Bonding technique

Compiled by: Slawomir Chorek

Articles

Bonding technique

A short course in basic concepts.

Table of contents:

Adhesion

Cohesion

Surface preparation for bonding

Examples of correct bonding

Direction of forces on bonded joints

Application methods for 2-part adhesives

Adhesion

Adhesion is defined as the forces of adhesion between the surfaces of different materials. The physical forces of attraction or adsorption, known as Van der Waals forces (Van der Waals forces are long-range attractive interatomic or intermolecular interactions), are of primary importance in adhesion.
The interaction range of these intermolecular forces is much smaller than the mechanical roughness of the treated surfaces. Therefore, the adhesive must penetrate the roughness and completely wet the surfaces.
The ability of a liquid adhesive to wet the surface depends on the surface energy of the materials. The adhesive will only sufficiently wet the surface of a material if its surface tension is at least equal to or less than the surface energy of the material. Examples of the surface free energies of different materials at room temperature:

PTFE (Teflon): 18 mN/m
PVC : 40 mN/m
Polyamide 6/6: 46 mN/m
Iron: 2030 mN/m
Tungsten: 6800 mN/m

for comparison:

anaerobic adhesives: 30-47 mN/m

The table shows that metals are easy to bond, whereas plastics are often critical. Appropriate pre-treatment can have a positive effect on the surface energy of the parts to be bonded.
Adhesive failure occurs when the adhesive forces are less than both the cohesion forces and the external load.

Cohesion

The cohesion of an adhesive bond is defined by its mechanical strength, which is a manifestation of the mutual attraction of the adhesive particles. Destruction of the bond can occur as a result of

Detachment of the adhesive layer from the substrate – Adhesive failure
Destruction of the adhesive film – cohesive destruction
Destruction of the bonded material – structural failure.

Cohesive failure occurs when the intermolecular bonding forces of the adhesive give way to the cohesion force and the external load force.
According to the rule that a chain is only as strong as its weakest link, the adhesive and cohesion forces should be of similar magnitude.

Surface preparation for bonding

The stronger the bond, the more thoroughly the surfaces in the bond area have been cleaned.
Bond strength can be significantly increased by

Removal of foreign surface layers by degreasing or mechanical treatment.
Formation of new active surface layers by chemical treatment.

Degrease mating surfaces

The basis of a reliable joint is the complete removal of oil, grease, dust and other contaminants from the surfaces to be bonded, as these reduce the holding forces at the joint. All solvents that evaporate without trace from washed surfaces are suitable for this purpose.

Mechanical treatment

Metal surfaces often have an oxide layer that cannot be removed by degreasing alone.
It is then recommended that the surface be mechanically treated by sanding, grinding or roughening.
When sanding with sandpaper, make sure that the grit size is appropriate (e.g. 300 to 600 for aluminium, 100 for steel).
After any of these methods, the parts to be bonded should be thoroughly degreased. When bonding rubber parts it is recommended to mechanically remove any pressed or vulcanised layers.
Sandblasting plastics with hardened iron or electro-corundum powders has been found to be effective.
Rubber surfaces should be stripped of anti-adhesive agents using a solvent or sandpaper.

Chemical treatment

Some materials that are difficult to bond (especially plastics) require chemical treatment. The most common treatment is surface etching. The composition of etching baths is recommended by adhesive manufacturers in their instructions.

Examples of correct bonding

The properties and capabilities of adhesives should be considered at the design stage. For optimum results, only shear and/or compression forces should be applied to the bond.

Peel forces have an extremely negative effect on the bond, but can be avoided by modifying the design. The surfaces should be as large as possible in order to transmit high forces.

During assembly, care must be taken to ensure that the applied adhesive is not pushed off the parts. Chamfer the parts to be joined (chamfer angle 15-35°). It is also necessary to check the mutual positioning of the parts, as correcting them during the curing process will destroy the polymerisation chains formed, affecting the final strength of the bond.

When fitting parts into a blind hole, the compressed air in the hole can push the adhesive off the part being fitted. This can be avoided by using a vent hole or by dispensing the adhesive directly into the blind hole. When the mating part is pressed in, the adhesive is pushed up and fills the gap well.

When bonding parts with very different coefficients of thermal expansion, large tensile forces can be generated at the joint when temperature differences occur. The adhesive can transmit such forces in the shaft-hub joint if the inner part has a higher coefficient of expansion. Otherwise an interference fit must be used to ensure that the hub does not slip off the shaft.

Direction of forces on bonded joints

The figures on the left illustrate the correct distribution in a bonded joint. Structures with forces acting in the directions shown in the figures on the right (eccentric pull and peel) should be avoided.

Application methods for 2-part adhesives

Bond with a hardener in the form of a ‘varnish’. One of the surfaces to be bonded can even be prepared well in advance of the bonding process by applying a layer of varnish hardener beforehand.

Hardener in paste or powder form is added to the adhesive immediately before bonding. The open time determines the time before the parts must be assembled. Some adhesives require very thorough (even) mixing of both components.

Dosing by means of a dispenser with automatic mixing of the two adhesive components.

Glue in two chamber cartridges. Dispensing by manual or pneumatic gun. Cartridges provide a ‘ready made’, simple and cost effective dispensing system, replacing expensive dispensing equipment.

Bead-on-bead (drop-on-drop) adhesive application.

The classic A/B system. The adhesive components are applied separately to each surface and then joined together. The curing reaction only occurs when the two surfaces come into contact.

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October 9, 2023

MONOLITH – Leader in Structural Adhesives

Written by: Aleksandra Lewandowska, Sławomir Chorek

MONOLITH – Leader in Structural Adhesives

Structural Adhesives – Definitions

By definition, a structural adhesive is an adhesive that forms a stronger bond than the materials it is used to join. In practice, it is an adhesive that allows similar or dissimilar plastics to be bonded by participating in the final structural unit and its strength. Typically, the minimum bond strength expected is greater than 7 MPa.
MONOLITH structural adhesives are characterised by their high bond strength and hardness. They replace traditional material bonding or alternative other bonding methods. This group of adhesives includes epoxy, polyurethane and methacrylate based acrylics.

Structural Adhesives Division

This type of adhesive can be divided into two-component and one-component adhesives. A two-part adhesive contains two separate components in a non-reactive state. These must be thoroughly mixed in the correct proportions before use to achieve the desired properties of the cured adhesive. A one-component adhesive contains only one component that cures when exposed to certain environmental conditions or energy sources.

Comparison of structural adhesives and other material bonding methods

How do the properties of materials bonded with Monolith structural adhesives compare to other common bonding methods? The characteristics are shown in the tables below.

Structural Bonding vs. Mechanical Bonding

Mechanical Bondinge	Monolith Structural Adhesives
Structure
– Unsightly appearance – Difficulty in joining thin materials	+ Invisible on the surface + Easy bonding of thin, lightweight materials
The bonding process
– Requires drilling of holes – Difficult to paint – Requires additional sealing + Good to look at	+ Wipe the surface dry before bonding (acrylics) + Bond and seal in one go – Inspection usually results in material damage
Final performance
– Stress sources – May leak – Joint may weaken over time – Galvanic corrosion + Can be replaced	+ Even stress distribution + Excellent strength + Prevents corrosion – Difficult to replace/remove

Structural bonding vs. Welding

Welding	Monolith Structural Adhesives
Structure
– Causes surface imperfections – Difficult with thin materials – Unsuitable for joining dissimilar materials – Difficult with complex shapes	+ Produces smooth surfaces + Can be used with thin, lightweight materials + Can be used to create complex shapes + Ideal for joining different materials
The bonding process
– Causes surface distortion (welding heat) – May require additional sealing – Requires some skill to perform – Damages metal coatings – Usually requires finishing + Ready to use	+ Will not warp + Bonding and sealing in one operation + No special skills required + Little or no post-treatment – Longer working time
Final performance
– Sources of stress – Corrosion is present – Poor vibration characteristics + Good reception	+ Even stress distribution + Excellent strength + Prevents corrosion + Reduces vibration + Bond strength can exceed weld strength

Structural Adhesives vs. Sealing Compounds

Sealing Compounds	Monolith Structural Adhesives
Structure
– Forces too small for construction – Does not contribute to the overall structure – Requires more reinforcement/stiffening + Lower cost/litre	+ Contributes to the overall design + Requires limited bracing/reinforcement
The bonding process
– Requires solvent cleaning – May require primer – Usually slow cure + Usually no mixing required	+ Simply wipe the surface dry before gluing (acrylics) + Normally no primer required + Short bonding time – Requires mixing of ingredients
Final performance
– Typical bond strength <5 MPa – Not resistant to torsion of the structure – Sensitive to ageing + Gives 100% or more elongation	+ Bond strength >12MPa + Excellent strength

Structural adhesives vs. High performance adhesive tapes

High performance adhesive tapes	Monolith Structural Adhesives
Structure
– Do not contribute to the overall structure – Require more reinforcement/stiffening – Difficult to use for complex shapes – High cost per running metre	+ Contributes to the overall design + Limited stiffening/reinforcement required + For use with complex shapes
The bonding process
– Requires solvent cleaning of surface prior to bonding – Difficult to automate – Difficult to apply in corners – Tape cannot be repositioned after application – Requires high application pressure + Instant adhesion + Dry application	+ Simple dry wiping of the surface before gluing (acrylics) + Manual or automatic application + Easy to use on corners + Easier to bond uneven surfaces than smooth surfaces – Longer bonding time
Final performance
– Deformation sensitive – Bond strength <1MPa – Not resistant to torsion of structures – Very sensitive to temperature changes + Gives 100% or more elongation	+ No deformation + Bond strength >12MPa + Contributes to surface integrity + Limited temperature sensitivity

In summary, Monolith Structural Adhesive has a number of advantages that give it a significant advantage over other common bonding methods. A summary of the main advantages is given in the table below:

Best structural design
+ Bonding of different materials + Bonding of thin materials + Aesthetic bonding line	+ Contributes to the overall design + Limited stiffening/reinforcement required + For use with complex shapes
Best bonding method
+ Bonding and sealing in one operation + No special skills required + Gluing position can be changed + Adjustable bonding and working time + Powder coating possible	+ Simple dry wiping of the surface before gluing (acrylics) + Automatic or manual application + Easy on corners + Can be used on surfaces and coatings
Best performance
+ High fatigue resistance + High ageing resistance + No corrosion + Limited temperature sensitivity	+ No creep + Bond strength >12MPa + Contributes to the overall structure + Hardness

Principles of working with structural adhesives

The first step in the bonding process is surface preparation. The amount of attention we pay to this activity will pay dividends in terms of the durability of the bond created. Depending on the adhesive we are using, there are specific rules to follow. Acrylic adhesives usually require minimal surface preparation. Dry wiping may be sufficient. Their use is environmentally friendly and user friendly. Epoxy and urethane adhesives require prior degreasing of the surface with isopropyl alcohol (IPA). Some materials also require abrading (sanding). Plastics with low surface energy may require corona or flame treatment. In addition, primers are sometimes used to improve adhesion on difficult to bond materials.

It is important to design the process well. A few design rules can help. Structural adhesives are designed for shear and compressive loads. Tear and peel loads should be avoided. The width of the adhesive should be at least 2 cm. It is a good idea to conceal protruding edges to minimise the risk of material peeling. The effect of thermal expansion should also be considered. It may be necessary to use welds or mechanical fasteners in strategic locations, particularly in areas where tearing and peeling are unavoidable. The figures below show some of the rules for joint design:

Structural adhesives is a growing industry due to increasing market demand. The use of bonding methods is becoming increasingly widespread in the construction industry. An example of this is the strengthening of existing joints by bonding various reinforcing elements. Structural adhesives are also used as stabilising elements, for example as chemical anchors. All in all, despite some limitations, adhesives are becoming a serious alternative to traditional methods of joining structures.

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August 19, 2019

Metal bonding in the industrial sector

Written: Aleksandra Lewandowska, Sławomir Chorek

Metal bonding in the industrial sector

Bonding is not a fundamental method of joining metals. It is still a developing field. There are more popular methods using traditional mechanical techniques. However, there are times when it is worthwhile, or there is no other choice, and joining a material using a chemical binder is the method of choice. So when is it worth using this method?

When are we going to glue?

It is certainly not a good method for joining thick components. Adhesive bonding is worth considering when the resulting structure is required to have high stiffness combined with low weight. Such requirements are found in the transport structures industry. The first industry to use this technology was the aerospace industry. Later it was used in isothermal bodies, buses, cars and containers. Another reason is when one component is one or two rows smaller than the others. Adhesives are also used to bond metals to plastics made from another raw material – glass or plastic.

However, before proceeding, we should remember that we need to answer some important questions in order to have a good idea of the technological possibilities of making a glued joint. An indication for the use of adhesives can be the disproportion in the dimensions of the elements to be joined, which precludes the use of traditional joining methods. Sometimes it is the physical conditions that determine the choice of a chemical bonding agent that is indifferent to these conditions. Other reasons are safety considerations, as in the case of the replacement of rusted supports for the sun visor on the gas tank at the EC III power plant in Lodz. It is interesting to note that Monolith® EP 2579-1 adhesive was used in this case.

The advantages

No other technology gives us results like bonding. By joining metals with adhesives, there is no bimetallic corrosion or thermal deformation, and there is also vibration damping. Another advantage is that the strength of the materials being joined is fully utilised. The bonding process does not create stress, i.e. it does not weaken the parts being joined, as is the case with welding, for example. It also preserves the surface of the material, as there is no need to drill holes or screw or rivet. Another advantage is that adhesives seal the joints themselves, eliminating the need for additional sealants. Bonding makes it possible to join parts of different thicknesses. It is the only technology that allows stainless steel sheets to be joined without holes or overlaps and without discolouration.
A major advantage, especially in industrial bonding, is the much lower skill level required of the workers. Traditional mechanical joining processes often require special qualifications acquired through courses or schooling. With adhesive bonding, virtually any worker familiar with the technology can perform the task.

Bonding vs. other techniques

A similar method to bonding is soldering, but bonding has a fundamental advantage over soldering. It is a more versatile method and can be used with more materials. Soldering with soft solder produces a joint that is only slightly stronger than a bonded joint.
Welding has significant disadvantages. It introduces stresses that require additional thermal methods to remove, adding cost. In addition, components with very small cross-sections are subject to permanent deformation. There are materials that cannot be welded, such as steel and aluminium. Welding destroys the galvanic coating and permanently discolours the stainless steel sheet. This method of joining metals often needs to be accompanied by additional factors such as inert gas shielding or the use of special expensive electrodes.
Bolted joints are another common but expensive method. However, these joints are leaky and prone to bimetallic corrosion. Welding is used to join sheets in a small thickness range. However, it is difficult to achieve an airtight joint and spot welding causes stress concentrations. Press joints with small component wall thicknesses do not allow sufficient clamping forces to be achieved and the assembled components require additional machining, increasing the cost of this method.

Adhesive selection factors

The following factors should be considered when choosing the right adhesive
– The nature of the surfaces to be bonded – tinned or non-tinned,
– The exposure to corrosion,
– The temperature at which the joint will operate,
– Ease of assembly and mechanical properties
– The cost of the bonding process.

Adhesive types

A number of studies have been carried out to find the adhesives with the best bonding properties for specific materials. Adhesive groups with different chemical bases, dedicated to specific tasks, have been identified. Here are the basic groups of adhesives:

– Anaerobic adhesives – These are based on methacrylate resins. The metal acts as a catalyst. When there is no air, and therefore no oxygen, in contact between two surfaces, at least one of which must be metal, the adhesive changes from a liquid to a hard, flexible solid. Where is this type of adhesive used? It is useful for securing threaded connections (disassembly by heating to a temperature higher than the maximum for the adhesive), seating bearings, gears, bushes, hubs, or sealing the mating surfaces of gear housings and covers. The cure time of anaerobic adhesives is influenced by the activity of the material. Active materials include copper, mild steels, unhardened carbon steels and cast iron. Inactive materials include high alloy steels, hardened aluminium and galvanised surfaces.

– Cyanoacrylate Adhesives – These are one-component substances manufactured on the basis of methyl, ethyl and alkoxy. Ethyl based adhesives are the most commonly used. Polymerisation occurs due to the catalytic properties of moisture in the air. This type of adhesive has a very short reaction time. With these adhesives we can achieve a strong bond on steel or aluminium, but also on plastics and various combinations of these materials. Cyanoacrylate Adhesives have a wide range of applications as they are very fast and strong. Due to these properties, they are mainly used for joining small parts. They are used in the manufacture of surgical instruments and in automated applications.
– Epoxy Adhesives – These are two-component substances. They are manufactured on the basis of polymeric epoxy resins. They are used for structural bonding of: carbon steels, alloy steels, stainless steels, aluminium, non-ferrous metals, most hard plastics, ceramics, glass, concrete, minerals and wood, and for bonding these materials to metals. They are ideal for bonding small rigid components.

– Methacrylate Adhesives – These are chemically cured two-part adhesives based on methyl methacrylate. They do not require thorough surface preparation and reduce build-up fields. The primary use of this type of adhesive is to bond plastics, but they are also used to bond plastics to metal or metal to metal. In industry they are used in vehicles, wind towers or in metal and plastic structures.
– Silicones – Synthetic organosilicon polymers with a siloxane structure. They are divided into acetic silicones, methoxy silicones, alcohol silicones and addition silicones. Their main advantage is high flexibility. Acetic silicones are best suited for bonding metals. Adhesive silicones are also used to bond metals, but also glass and ceramics. Their main advantage is that they cure throughout their volume without shrinking. This property allows them to be used as assembly adhesives and sealants. They are used where food contact approval is required.

– MS polymers (MS silanes) – These are polymers modified with silanes. They are an intermediate between polyurethanes and silicones. They are highly flexible and have high bond strength. They have good adhesion to metals and many other substrates. Advantages include UV resistance, better adhesion than polyurethane with an activator and cohesion, which can be selected according to circumstances. Thanks to these properties, the adhesives in this group are used for bonding materials with different coefficients of thermal expansion, in environments with constant humidity or in joints subject to vibration. They are also used to bond large components consisting of thin shells supported by stiffeners.

How do you bond metals?

As with other materials, it is important to start with good surface preparation. If a component is large or its mass is critical, various etching and coating processes are used, such as cataphoresis. These are complicated processes that require chemical baths and special health and safety precautions. A simpler approach is to perform the degreasing or primer application itself, which is designed to bind contaminants. The next step is to apply the adhesive. There are several techniques. The key is to apply and adhere to the other surface in such a way that there is no air between the two parts. The glue must be removed from the containers in the correct way. Rare glue in cartridge tubes or bottles is designed to displace air and flow around the joint by itself. This process occurs, for example, in threaded joints where adhesives with uniform capillary properties are used.
An air bubble is always a source of discontinuity in the joint and can cause delamination. Therefore, in structural joints, the problem of air bubbles in the joint is a major issue to be addressed. In these cases, it is not only the application of the adhesive that can be a problem, but also the application of the surface. Structural or process pockets cannot be used as they can trap air which will displace the adhesive to the outside.
What about using a thixotropic adhesive? This is a dense adhesive that contains fillers to increase strength, resist peeling and resist vibration. Such high strength adhesives are subject to increased notching, which makes them similar to metals. Therefore, the adhesive must be applied in a continuous stream without air bubbles. For this purpose, industrial packaging methods are used and the adhesive is applied directly from the packaging. For smaller joints, special applicators and cartridges are used (Figure 6), and for large parts, pumps are used to deliver the adhesive through hoses directly from drums or buckets.

The next step is to join the elements together. Here we make the very common mistake of pressing the elements together. In most cases we should not do this. They just need to be put together and fixed in place. Unless, of course, they deform, bounce or fall off under their own weight, in which case it is necessary to secure their position until the desired weld is achieved. But again, this is not a matter of pressing. Spacers, metal or rubber washers are used to ensure the correct thickness of the adhesive layer. A good example is responsible structural bonding, where adhesives with special glass beads are used to ensure the correct layer thickness.
With traditional mechanical methods of joining metals, such as welding or brazing, once the parts are joined, further processing of the product can begin. This is not the case with bonding, which can be a disadvantage. We have to set the bonded parts aside for a period of time while the weld forms. Technologists are working to minimise this time, which is so valuable in any manufacturing process.

Reduced adhesive setting time

Even in the production of adhesives, attempts are made to develop technology to achieve the shortest possible time for the bond to form. Adhesives with a booster, fast two-component adhesives, no-mix systems or activators are produced. Time can also be gained by optimising the adhesive application method. It is up to manufacturers and suppliers of dispensing equipment to optimise the process. The aim is to apply the fast setting adhesive as quickly and efficiently as possible. Pump performance is increasing, as is the accuracy of component mixing. Automation of the application and component assembly process is increasing. Closed loops are being created. In each of the next five years, the cost of maintaining adhesive processes will almost halve. As a result, smaller and smaller manufacturers can afford to use this method.

Summary

There are many ways to join metals. The key is to choose the right technology to achieve the desired effect. In modern industry, adhesives play an increasingly important role in joining metals to various materials. Hence the variety of types. They have made it possible to join materials that previously could not be joined and have greatly expanded the technological possibilities of modern industry. Bonding is often an irreplaceable method. In the future, when the barrier of intermolecular bonding is broken, traditional mechanical technologies will probably be history.

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March 5, 2018

Health and safety in the bonding process

Writting by: Katarzyna Gajda

Health and safety in the bonding process

Health and safety at work… For the ‘ordinary’ employee, it is usually associated with boring training courses. We want to change that! The purpose of this article is to make you aware of the importance of complying with and enforcing health and safety standards and rules for your employees, with particular emphasis on those relating to the bonding process.

Steps in the bonding process

In this article we will discuss the bonding process from a health and safety perspective. It consists of the following steps

Familiarise yourself with the adhesive data sheet.
Preparation of the surface to be bonded.
Preparing the adhesive.
Applying the adhesive.
Joining the parts.
Drying and curing.
Finishing the joint.

Read the adhesive safety data sheet

Unfortunately, this step in the bonding process is often overlooked. We should adopt good practice and always start by reading the MSDS of the adhesive. Safety data sheets are produced in accordance with Regulation (EC) No 1907/2006 of the European Parliament and of the Council (known as REACH). Each sheet is structured in the same way – it contains the date of preparation and 16 thematic sections. In terms of health and safety, we should focus on the following five sections:
2. hazard identification
4. first aid measures;
8. exposure controls and personal protective equipment
11. toxicological information
13. waste management.

Hazard Identification – in this section we will find out what substances we are ‘dealing with’ and how they are classified and labelled (according to Regulation (EC) No 1272/2008 of the European Parliament and of the Council on classification, labelling and packaging of substances and mixtures). Pictograms are shown in Figures 1-3.

First aid – we should read this section very carefully before starting work. We will learn about the main symptoms and effects (acute and delayed), as well as how to seek immediate medical attention and how to treat an injured person in the event of an accident at work. Should we witness an accident or be the one who suffers an accident, we will know what to do. It is also good practice to keep the safety data sheets for the substances (adhesives) in a place where all the workers can access them and the medical services can consult them if necessary – THIS WILL REDUCE THE RESPONSE TIME! It is worth noting that doctors and paramedics are not chemists, let alone experts in adhesives, so they could obtain the relevant information from a reliable source such as safety data sheets.

Exposure controls and personal protective equipment – this section provides information on the maximum allowable concentration (MEL) of the substance in the workplace that needs to be monitored. It also indicates what personal protective equipment (PPE) should be used during work. As a reminder – Figure 4 shows the most commonly used safety phrases in SDSs.

Figure 4: The most common prescriptive phrases in SDSs for adhesives (from left): eye protection prescriptive, hand protection prescriptive, respiratory protection prescriptive.

Toxicological information – reading this section may seem superfluous at first, but… if we work with a chemical for 8 hours a day and do not follow health and safety rules, this chemical may have a toxic effect on us and this toxicological information may be extremely important for our doctor, for example. Maybe prevention is better than cure? Absolutely! So let’s read this section before we work and do the work in a safe way and we will never experience these ‘toxic issues’ first hand.

Waste management – safe working should culminate in proper waste management. Some chemicals cannot be disposed of in ‘normal’ waste because of the risk of contamination or poisoning of living organisms. There are also substances that react strongly with water or water vapour – this can lead to exothermic reactions. These in turn can create a fire hazard.

Once you have read the MSDS of the adhesive in detail and understand the risks of working in breach of health and safety regulations, you can move on to the next stage of the bonding process.

Preparation of the bonding surface

Depending on the materials we are dealing with, the cleaning/preparation of the bonding surface varies. There are two main methods: mechanical and chemical. In the case of mechanical treatment we should pay particular attention to the use of dust masks, gloves and goggles. Chemical treatment involves the use of a cleaner or primer – so follow the information on the chemical and technical data sheets of these chemical preparations.

Preparation of the adhesive

Once we have a suitably prepared bonding surface, we can proceed to prepare the adhesive. If we are using a single component adhesive we can skip this step, but if we are using a two component adhesive we need to be aware of the volume or weight ratio in which the components need to be mixed. Sometimes it is possible to buy a special applicator that will apply the glue in the correct volume ratio – this will make the job much easier. Those adhesives that need to be mixed in the correct weight ratio are best mixed in a separate container. Estimate how much glue you will need, because mixing too much glue is both a waste of money and a risk of inhaling more glue fumes. Most people think of the smell of the glue, thinking that the one that smells bad is more ‘toxic’ – nothing could be further from the truth! Let’s compare two types of glue – methacrylates and epoxies. The smell of methacrylates is pungent, suffocating, ‘dental’, while epoxies have a peculiar but less irritating smell – you might think they are less harmful than methacrylates, but it is quite the opposite. It’s also worth mentioning that packaging containing chemicals should always be sealed – inhaling some vapours can be bothersome and even harmful to us. In addition, different fumes can react with each other in different ways – which can lead to disaster. We should also remember to ventilate the room properly. In production, use additional bench ventilation. If the vapours are lighter than air and rise upwards, use top ventilation and if they are heavier, use bottom ventilation. An example of an adhesive whose fumes are heavier than air is cyanoacrylate. Using top-down ventilation when working with this adhesive would result in additional worker exposure to the substance, as the vapours would be mechanically drawn up into the worker’s upper respiratory tract. Such ventilation would do more harm than good. On the other hand, if we are gluing in a domestic environment, we should open a window during the work – if the conditions outside are favourable – or when the work is finished. Nothing is better than a breath of fresh air!

Application of adhesive

Remember to wear protective gloves when applying the adhesive – this will prevent your hands from getting dirty and some substances from entering your body through the skin. Wearing gloves greatly improves our safety in the workplace and reduces exposure to chemicals. To apply the adhesive, use brushes, rollers, applicators or dispense it directly from the tube – the latter two are best from a health and safety point of view.

Joining the parts

Depending on the project or what we are bonding, the joining of the parts is done differently. If we are gluing small parts, the joining is done ‘by hand’, whereas if the process takes place in a production company or the parts to be glued are very large, we must follow the health and safety instructions for the process, which are drawn up by the employer in consultation with the company’s health and safety department. Once the parts have been bonded, we leave them to cure. There are, of course, exceptions… When using solvent-based adhesives, the joining of the parts is a little different. We apply glue to both surfaces. We then wait for the solvent to evaporate (we check this by touching the glue layer – if it doesn’t stain our gloves, we can join the two surfaces). At this point we can put the parts together and wait for the glue to cure – this is called contact bonding.

Allow to cure time

Someone might ask, ‘Why not dry the weld to speed it up?’ – Crazy? Yes… and no. In most gluing processes, drying involves leaving the glued parts ‘alone’ and waiting for the glue to set well. In some industries, such as bookbinding, mechanical drying is used, which shortens the whole process considerably. However, it is important to remember that not all adhesives can be dried – it is worth contacting our experts to find out what can be done to speed up the process. For example, single component polyurethane and cyanoacrylate adhesives will absorb water from the air as they cure, so it is essential that the room is properly humidified when using polyurethanes and cyanoacrylates. Epoxy or methacrylate adhesives, on the other hand, bond through the chemical reaction of the activator with the base. In the case of solvent adhesives, after contact bonding, the bonded parts must be left to allow the residual solvent in the adhesive to evaporate. So remember, the less contact you have with the bonded areas, the better. The adhesive from a single component emits few harmful substances, but when we bond many components at the same time, the concentration of these substances can cause the Maximum Permissible Concentrations (MPC) to be exceeded.

Finishing the joint

As someone wise once said, ‘Pretty things sell better’, so as well as being durable, glue joints should be as invisible as possible. To achieve this, we sand and rub down the glue and paint the whole piece. So remember to protect your eyes, hands and respiratory tract during this stage.

Summary

The bonding process requires practical eye, hand and respiratory protection at all times. Use safety goggles, gloves and dust masks – they are inexpensive and improve comfort. In addition, ensure that there is adequate ventilation in the areas where you are working, close chemical containers and tighten them securely when not in use and, above all, start each job by familiarising yourself with all available documentation on the product and process in question (e.g. your company’s H&S manual). Following all the advice in this article will not only improve the safety of those involved in the bonding process, but will also improve their working comfort and the quality of the bond. When finishing work with all types of adhesives, also consider the environment by making appropriate arrangements for waste storage and disposal.

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December 15, 2016

Design and construction of composite bonding

Luxury yacht Cruising rivers – depositphotos.com

Written: Katarzyna Gajda, Sławomir Chorek

Design and construction of composite bonding

Although there are many guides to bonding composites on the internet, it is worth taking a moment to read the advice on bonding these materials.

Composites

First of all, it is important to remember what composites are. They are a wide variety of materials with a heterogeneous structure consisting of two or more components (i.e. phases) with different physical and chemical properties. It is extremely important to note that the properties of a composite material are not the sum or average of the properties of its components, which means that the bonding process of such materials can initially appear problematic and unpredictable.

Composite materials are widely used and can be found in cars and trucks, motorboats and yachts, among other things. They are also used to make propellers for wind turbines and architectural elements such as bridges. These are just a few examples of where composites are used. It is the diversity of these materials that allows them to be used in so many areas. The most common are glass fibre, carbon fibre and aramid composites with resins mainly polyester and epoxy.

Advantages of composites

The advantages of composites are many, and these fibre-reinforced plastics are characterised by

a good stiffness to weight ratio – light and strong structures
high mechanical strength
low specific weight
high mouldability.

Composite bonding

Designers of composite joints can face some difficulties due to the reduced resistance of these materials to local loads. For example, localised fasteners do not work well when joining these materials. The use of such fasteners can result in cracking or pull-out. For designers, the stiffness of the overall structure/component to be joined and the ability to achieve a defined overall shape are very important. The aerodynamics and hydrodynamics of the structure are also extremely important, as well as the aesthetics of the joints. It is well known! Beautiful things sell better…

How can composites be joined?

Depending on what we want to bond, we need to prepare accordingly. We need to understand the materials we are joining and choose the best adhesive to achieve a permanent bond. Bonding composites to other composites – in this case mainly gluing/bonding composites to give them the right shape and size – is very important when bonding cockpit components in a car, for example.

Bonding composites to a structure – usually steel or aluminium – in which case the composite is usually intended to enhance the aesthetics of the product. The most important and strongest structure is ‘inside’, but appearance is also very important – who would buy an ugly yacht?

It is also common to glue on all sorts of decorative/finishing elements, e.g. door frames or nameplates. The combination of these materials must be simple, durable and aesthetically pleasing. And the assembly of the various brackets and fasteners also requires very high strength. In all these cases, the use of adhesives is extremely convenient and aesthetically pleasing.

Disadvantages/weaknesses of bonding composites

Bonding always has ‘some’ disadvantages, and the same is true for bonding composites. Below are the main disadvantages of bonding these materials:

It is necessary to improve the technological process in order to achieve 100% reproducibility of the results – to ensure adequate stabilisation of the glued elements and the whole structure when the total curing time is reached.
The gluing process extends the whole technological process by an additional operation.
During the curing time, the glued structure cannot be moved, which is connected with the need to store and immobilise the glued elements somewhere.
Some adhesives require special surface preparation, which prolongs the process and increases costs.
When bonding composite materials, the different coefficients of thermal expansion must be taken into account.
In many cases it is necessary to remove adhesive drip – too much drip has a negative effect on the aesthetics of the bond and increases the cost of the entire bonding process. This is related to the manual dispensing of the adhesive – the drip rate can reach 30-50%. Too much efflorescence = wasted adhesive and therefore higher costs for the entire process.
Adhesive is an additional material, especially as it is much more expensive than native materials.

Advantages / Strengths of composite bonding

Having discussed the disadvantages of composite bonding in detail, it is important to look at the advantages that often lead manufacturers to choose this method of joining materials.

Bonded structures are lightweight and stiff (favourable weight to stiffness ratio).
Composites are not resistant to local loads (which makes riveting impossible, for example). However, bonded structures are much better at withstanding such loads.
Bonded joints are very airtight – many joints are resistant to water, rain, salt spray and unwanted ventilation and can therefore be used in marine applications.
Adhesives allow composites to be bonded to a wide range of materials including: metals, plastics, glass and even wood. Despite the different coefficients of thermal expansion, the different materials bond effectively.
The aesthetics of bonded joints are much better than, for example, riveted joints. Bonding makes it possible to create joints that are invisible to the untrained eye.
Bonded composites are more resistant to vibration and varying loads. This is an important feature in transport applications, for example, but also in wind turbine propellers, where resistance to shock and fatigue is critical. For example, in the case of wind turbine propellers, resistance to many millions of cycles. This is particularly important for structures that run continuously.

What do I use to bond composites?

To select the ideal adhesive for bonding composites, it is important to understand a number of factors that affect the bonding process. You need to know what is being bonded, at what temperatures the process will take place, under what conditions the whole structure will be used and what loads it will be subjected to.
If you ask anyone with even a basic knowledge of adhesive technology what the best adhesive for composites is, they will answer without hesitation: “METHACRYLATE! This is usually the case: methacrylate adhesives are ideal and very convenient.

Methacrylate (acrylic) adhesives are ideal for bonding composites to metals. They are two-part, chemically curable adhesives based on methyl methacrylate that, when cured, resemble a hard plastic with the right adhesive-specific properties. This is why they work so well for bonding composites.

Methacrylates do not require any surface preparation, degreasing or priming prior to bonding. Methacrylates dissolve gelcoats and polyester resins very well without damaging the bonded surfaces. Bonded joints are also resistant to temperatures up to 120°C, water, petrol and various types of oil. Bonded joints in composite materials are airtight and isolate the bonded materials (phases) from each other. In addition, the adhesive layer dampens vibrations and noise and, if it is thick enough, bridges the differences in the coefficients of thermal expansion of the materials to be bonded.

One of the most important properties of bonded joints when bonding composites is elongation. Details are given in Figure 1. It should be noted that these are indicative values and there are no clear examples. If you want to use an adhesive that has a high elongation, you need to look at the detailed technical data sheet where the data – preceded by many tests – are given. For example, the elongation of Monolith 342-1 – an adhesive that is very good for bonding composites – varies between 100% and 125%.

Advantages of methacrylate adhesives:

They require no preparation of the bonded surface – no degreasing, priming or roughening is required.
They have strong solvent properties for most polyester resins and gelcoats.
They will not damage the parts being bonded.
They have short cure times.
They are highly resistant to temperatures up to 120 ^oC, water, petrol and oils.

Disadvantages of Methacrylate Adhesives

One of the disadvantages of methacrylate adhesives is their flammability and the explosiveness of their vapours, so it is advisable to carry out the gluing process in production areas with very good ventilation or under a local exhaust hood. Always prepare as much glue as will be used. Another disadvantage of methacrylates is the strong odour of the glue, but it should be noted that it is not harmful to health.

The price is often cited as one of the main disadvantages of methacrylate adhesives, but in many cases it is better to choose a more expensive adhesive that has a short curing time and virtually no preparation time for the glued surface (saving time in a complex technological process can be crucial). For the layman, methacrylate glue is expensive, but it makes up for its price by being easy to use. It is hard to mess up with this adhesive.

Composite adhesives from our range

Our range includes MONOLITH and PLEXUS branded methacrylate adhesives, which are well suited to bonding composites. These adhesives require no surface preparation and are safe – reducing VOC and dust emissions into the working environment.

One of the most commonly selected adhesives for bonding composites is Monolith 342-1, which is most often recommended to transport equipment manufacturers due to its properties, short time to initial strength and high tolerance for imperfections in the mixing ratio of this two-part adhesive. Another recommended adhesive for bonding composite materials is Monolith 345-1, which offers a unique combination of high strength, excellent fatigue life, very good impact resistance and high environmental resistance.

PLEXUS brand adhesives perform very well in the automotive and transportation industries due to their short cure times, high oil resistance, ease of use and high fatigue resistance. For a detailed specification of these adhesives please click here.

Epoxy Adhesives in Composite Bonding

In addition to methacrylate adhesives, epoxy adhesives are also used to bond composites. In the case of these adhesives, it is best to contact our technical advisor and carry out a test bond, as different composites may react differently to the adhesive. One of the most commonly recommended epoxy adhesives for bonding composites is Monolith 2510-1. This adhesive can withstand high mechanical loads and is suitable for bonding body panels and spoilers in the automotive industry and in vibration damping assemblies. It allows the bonded parts to be coated with a powder coating.

Another adhesive recommended for bonding composites is the hybrid adhesive Monolith SE 131-1 and 132-1, which is a derivative of epoxy and MS polymer. It contains no solvents, isocyanates, silicones or PVC and is convenient to use as it is virtually odourless. The main advantage of this adhesive is its elongation, which can reach over 200%.

Flexible adhesives (polyurethanes and MS polymers)

Polyurethanes and MS polymers work very well for bonding composites and are also paintable. Polyurethanes are also flexible adhesives, capable of elongation in excess of 100% (sometimes as much as 400%), but it should be remembered that such results are achieved with a long joint and a suitably thick bond. When using polyurethane adhesives and MS polymers in this process, it is important to consider their cure time.

When discussing flexible adhesives for composite bonding, MS polymers should also not be overlooked. They are more expensive than polyurethanes, but they are easier to use because they do not require any special surface preparation, which simplifies the whole process and saves technological time. Like polyurethanes, they can be painted and even withstand powder coating, which would destroy a polyurethane joint, for example. Although MS polymers have been on the market for more than 10 years, they are still rarely used, but it is worth knowing their advantages and starting to use them.

One of the disadvantages of single component flexible adhesives is that they take longer to cure. This time is affected by the humidity in the room where the bonding is taking place, as these adhesives absorb moisture from the air. The curing time is also affected by the width of the gap – the wider the gap, the longer the curing time of the bond.

These adhesives cure at a rate of 2-4mm/day. Under optimum conditions, a 10 mm deep joint will cure in 3-5 days. Although initial strength is achieved in 24 hours and the bonded parts can be transported, final strength will have to wait.

Two-component adhesives are better – the curing time is about an hour, which significantly shortens the technological process, but these adhesives are more expensive because we have to use special glue dispensers during the bonding process. In addition, polyurethanes require primers and thorough surface preparation.

Summary

The use of our adhesives in bonding composites depends largely on the creativity of the joint designer. Trials are extremely important to determine if a particular type of adhesive will work for a particular type of joint – we encourage you to read the article ‘Structural Bonding of Thermoplastics’. Our experts are available to answer any questions you may have about bonding these different materials – please contact us for a consultation. Remember to use tested and reliable adhesives when bonding composites, read the technical data sheets for details.
The bonding of glass fibre reinforced composites is the very concept of composites. Bonding technology provides structural reinforcement and most of the benefits for which composites are used in structural applications can be exploited..

Bibliography

Piekarczyk M., Application of adhesive joints in metal structures, Construction. Czasopismo Techniczne, Wydawnictwo Politechniki Krakowskiej, 1-B/2012, Zeszyt 2, Rok 109.
Proxima Adhesives, PLEXUS adhesives
Proxima Adhesives, Structural bonding of thermoplastics

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August 18, 2016

Hull bonding of laminate yachts

Written by: Zygmunt Tyska

Hull bonding of laminate yachts

Yachts

With more and more sailing enthusiasts owning motor or sailing yachts, some even building their yacht “from scratch”, we would like to introduce you to the use of PLEXUS adhesives in yacht building. At sea, every sailor expects a boat he can rely on – durable and resistant to harsh conditions. Therefore, many boat and yacht building companies are inclined to use newer and newer technologies in their construction. PLEXUS adhesives fit perfectly into the manufacturers’ expectations.

Like road vehicles, yachts are subject to dynamic wave action. Vehicles are equipped with shock absorbers that reduce structural loads and improve ride comfort; in the case of yachts, this role is fulfilled by PLEXUS adhesives, which replace rigid joints in the yacht’s structure. The diagram below (Figure 1.) shows the shock-absorbing contribution of the adhesive in the hull structure.

Figure 1: The cushioning contribution of PLEXUS adhesives to the construction of the yacht’s hull. “Rigid” curve – rigid laminated construction. Damped” curve – construction bonded with PLEXUS adhesive.

The same amount of energy is absorbed in both constructions, but a yacht glued with PLEXUS adhesives is subjected to gentler loads, which has a positive effect on the comfort of sailing and increases the life of the yacht.
PLEXUS adhesives have the necessary certificates from regional classification societies.

PLEXUS adhesives in yacht bonding

PLEXUS offers a wide range of methacrylate adhesives, but only a few are suitable for bonding basic yacht components. Ideal for these purposes are those that have a relatively low modulus of elasticity and allow a large weld thickness. PLEXUS MA425 is most often used in the production of Polish yachts. However, in the case of larger yachts, the parameters of this adhesive may not be sufficient and another PLEXUS adhesive should be selected.

For the average amateur yachtsman, using PLEXUS adhesives for gluing yachts will bring the following advantages

Improve the quality of the swim.
Reduce the magnitude of loads, resulting in a reduction in the amount and size of damage.
Increase fatigue strength.
Extend the life of the yacht.

An example of the use of PLEXUS adhesive for bonding a yacht hull

The hull of the motor yacht shown in the photo (Fig. 2) was built at the GEMINI GROUP GDANSK shipyard.

A bottom insert weighing 1200 kg was bonded into the hull with a length of L=50′ (Figure 3). The adhesive used was PLEXUS MA557, which allowed for a 10-37 mm adhesive layer and a shelf life of 80-90 minutes.

Glue was applied using cone-shaped bags to flatten the liner to the desired width and thickness as it was pressed against the jacket, requiring the width, length and frequency of the applied glue rollers to be selected accordingly (Figure 4).

Bonding operations, including mixing the adhesive components, applying them to the surfaces to be bonded, and placing and pressing the insert, took 75 minutes, and bonding the deck to the side plating took even less time. Bonding significantly reduces the time required to join yacht components, and allows for the joining of inaccessible parts that would be impossible to join using lamination. If yachts were to be built on a larger scale, it would be possible to mechanize the application of glue, which would greatly improve the entire yacht production process.

Working safely with PLEXUS adhesives

In the course of any work, it is extremely important to follow health and safety rules. PLEXUS adhesives allow working in safe conditions – they emit minimal amounts of vapors harmful to human health. With proper organization of work, the maximum permissible concentrations (MPC) are not exceeded, and working in such conditions does not threaten the health and life of employees.
In the shipyard of GEMINI GROUP GDANSK, up to 170 kg of glue was used, and the working conditions were very good, the concentration of glue vapors was much lower than the permissible standards.

Advantages of PLEXUS Adhesives

Preparation for bonding does not require special procedures.
Production costs are reduced.
Bonding significantly reduces the time required to join components.
Joints are strong and durable.
Allows simplification of construction.
Improves worker health and safety.

Curiosity

There is a well known case from the now defunct VACE shipyard in Gdansk, Poland, where a yacht ran aground while in use and its hull was badly damaged, but the weld that connected the underwater part of the stainless steel hull to the upper part of the laminate hull was not damaged. PLEXUS MA550 adhesive was used to make this joint, and it turned out to be extremely strong and very good at bonding stainless steel to laminate.

Summary

PLEXUS adhesives are widely used in boatyards for bonding laminate yacht hulls. Thanks to their strength and resistance to harsh conditions, they provide solidity and safety during sailing. PLEXUS adhesives replace traditional rigid joints to absorb the impact of waves and improve sailing comfort. They also make yachts more durable and significantly extend their service life. An example of the use of PLEXUS adhesives is the bonding of the bottom liner to the yacht’s hull, which reduces the time required to join the components and provides strong, durable joints. They are extremely effective and meet the highest standards of yacht builders.

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January 12, 2016

Flexible structural bonding

Written by: Sławomir Chorek, Marek Bernaciak

Flexible structural bonding

For bonding materials with significantly different thermal expansion coefficients that are exposed to vibration, we recommend MONOFLEX MS 611-1. In addition to MS 611-1, we also offer a similar adhesive Alpha DP007.
This is an elastic adhesive – a sealant based on a silane-modified polymer. This adhesive cures to a rubber-like form due to moisture in the air. In summer and during the heating season it is important to ensure that the room in which the gluing process is carried out is sufficiently humid.

Purpose of MONOFLEX MS 611-1 adhesive:

Bonding of floors of buses, trams, refrigerated trucks, semi-trailers, etc.
Bonding of vehicle body panels,
Bonding of multi-layer panels,
Bonding of glass panes in skylights, covers in machine tools, etc.
Bonding of sheet metal reinforcements, doors and sheet metal covers, etc.

Advantages of MONOFLEX MS 611-1:

has excellent adhesion to metals, steel, stainless steel, glass, plastics, plexiglass, paint, etc.
The joint acts as a vibration damper, compensating for stresses caused by differences in thermal expansion,
Prevents corrosion – joints are sealed,
One component – easy to apply,
UV resistant (no yellowing),
Paintable – can be painted after curing.

BASIC TECHNICAL DATA OF MONOFLEX MS 611-1

Feature	Value
Density [g/cm³]	1,5
Volume change (DIN 52451) [%]	< 2
Tixotropy	excellent
Skin formation time (DIN 50014) [min]	10 – 15
Cure Rate (DIN 50014) [mm/24h]	3
Shore hardness (DIN 53505)	60
Tensile strength (DIN 53504) [MPa]	3,0
Elongation at break (DIN 53504) [%]	230
Tension at elongation 100% (DIN 53504) [MPa]	1,5
Temperature resistance [^oC] – short term [^oC]	-40 / +100 do 120
Operating temperature [^oC]	+5 / +40

Przeznaczenie kleju MONOLITH SE 131-1 i SE 132-1:

MONOLITH SE 131-1 and SE 132-1 (formerly SE 105-1, now replaced by SE 132-1) are recommended for flexible structural bonding of components made of various materials, including those that are difficult to bond, with high impact resistance. SE 131-1 has a higher viscosity than SE 132-1 and allows bonding with a maximum gap of up to 5 mm instead of 0.5 mm. SE 132-1 is also suitable for coating and encapsulating electronic components. It is self-leveling.
These are two-part adhesives based on a modified epoxy hybrid that cures by chemical reaction to a hard elastic mass:

For elastic bonding of metals, steel, difficult to bond plastics, for bonding a wide variety of materials,
Elastic sealing of seams and joints in vehicle construction, containers, ventilation and air-conditioning systems.
Bonding of construction elements with high requirements for impact resistance – bonding of glass panes in military armoured equipment (opinion WZI – 985/WT concerning SE 105-1), in bank vehicles, etc.

Benefits of MONOLITH SE 131-1 and 132-1 adhesives:

adheres to many substrates, no primer required,
high viscosity, will not run off vertical surfaces,
has no shrinkage, the joint is even on the surface, without tension,
does not contain solvents, isocyanates, silicones, PVC, is virtually odourless,
is practically odourless, has a high tolerance to disproportioning of mixed components,
can be painted after curing
cures at room temperature
easy to apply – can be used in most weather conditions
soft and flexible

PODSTAWOWE DANE TECHNICZNE KLEJU MONOLITH SE 132-1

Feature	Value
Mixing ratio (by volume)	2:1
Tixotropy	excellent
Shore hardness (DIN 53505)	55 – 85
Tensile strength (various materials, 0.5 mm gap) [MPa]	3,0 to 7,0
Peel strength – aluminium (ISO4578):	140 – 160 N/25mm
Elongation to break (DIN 53504) [%]	150 – 200
Temperature resistance [^oC] – short term [^oC]	-40 / +100 +150

For more detailed information, please refer to the Technical Data Sheets and Material Safety Data Sheets.

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July 11, 2015

Bonding of conveyor belts and rubber linings

Written: Marek Bernaciak

Bonding of conveyor belts and rubber linings

with PKT adhesive

Introduction

This study is intended as a guide for those who wish to carry out cold bonding of industrial rubber conveyor belts and rubber to metal bonding, for example in the manufacture of bumpers or rubber linings. Proxima Adhesives offers a special high-strength adhesive, MONOLITH PKT, for this purpose, which enables flexible and durable joints to be made.

General notes on rubber bonding

As an adhesive substrate, rubber is a specific substrate. It oxidises easily and covers itself with a passive layer of brittle ‘crust’. This process is very rapid under atmospheric conditions, especially when the rubber is exposed to ozone and sunlight.

Therefore, the basic operation when bonding rubber is to remove the oxidised layer using wire brushes, scrapers, coarse sandpaper or other mechanical means.

Bonding rubber conveyor belts

Bonding rubber conveyor belts with adhesive is probably the most common method, both for bonding new belts and in emergency situations. It allows a joint to be made that is resistant to weathering, repeated bending and scraping.

The basis of a good splice is

Correctly cut and align the tape,
Apply the adhesive in accordance with the technical data sheet,
Apply sufficient pressure and leave the bonded tape in place until the adhesive is fully cured.

Preparing the tape for bonding

Before applying the adhesive, the following operations must be carried out:

Cut the tape at a 60° angle with an allowance of approximately 1.5 tape widths.
Both ends of the tape should be staggered so that any scrapers do not catch and tear the splice. The number of steps should be equal to the number of plies minus one (see sketch).

Once properly trimmed, care should be taken to ensure that the adhesive surfaces are well roughened using tools such as rotary wire brushes.

Applying the adhesive

MONOLITH PKT adhesive must first be thoroughly mixed with the amount of hardener supplied. If only part of the adhesive is to be used, weigh out the appropriate amount of adhesive using an accurate scale. Do not measure the amount of adhesive by eye. An error can significantly reduce the strength of the bond.

The mixed adhesive should be applied to the surface of the tape to be bonded using short bristle brushes. The first layer of adhesive should be allowed to dry more than the second (see Technical Data Sheet). If the substrate is very absorbent, apply three coats of adhesive. The first two coats should be thoroughly dry.

The last layer of adhesive should only be allowed to dry to the so-called dry touch, i.e. to the point where touching the finger causes only slight adhesion of the finger to the adhesive (the adhesive does not stick to the finger).

It is then necessary to press the two parts of the tape together using a thick (preferably 2-3 cm) plywood or even steel plate (8-12 mm). Press the two parts together with a roller (8-16 mm) or a heavy hammer (approx. 2 kg). Accuracy of pressing is essential for a good bond.

Bonding rubber flooring

The bonding of rubber linings is typically used in the following types of structures:

Chemical resistant linings for tanks, gutters,
Abrasion resistant lining of chutes, cyclones,
Lining of drive drums in mining belt conveyors, etc,
Manufacture of bumpers or their components

Preparation of the rubber surface

Thoroughly grind the metal (usually steel) to white metal, leaving as rough a surface as possible. If only part of the steel structure is to be rubber lined, sand the adjacent area as well (approx. 100 mm from the proposed rubber edge). Then apply PKT Metal Primer to the entire sandblasted metal surface. If no primer is available, MONOLITH PKT Adhesive mixed with hardener according to the technical data sheet can be used to prime the steel).

Applying the adhesive

We do not apply the adhesive until it has been thoroughly mixed with the hardener. We try to use the entire batch of mixed adhesive within the time specified in the technical data sheet.

Bonding to rubber is applied in the same way as for conveyor belts.

Glue on steel is applied similarly, except that the first layer of glue is dried very thoroughly. This may mean that the drying time is twice as long as for rubber. Always use a short bristle brush to apply the adhesive.

Tip

Our data reflect the current state of chemistry and technology and do not claim to be exhaustive. The best safeguard against possible errors, for which we cannot accept any responsibility, is to carry out your own tests. In this way, the variable data, which depend on the application, working method and materials, will be confirmed in each case under specific conditions.

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November 26, 2014

Structural Bonding of Thermoplastics

Written by: Marek Bernaciak

Structural Bonding of Thermoplastics

New MA Adhesives for Bonding Plastics and Metals

Introduction

Structural bonding of components during assembly using adhesives is a rapidly developing technology in industry. This article provides examples of the use of adhesives in the automotive and shipbuilding industries, where it has been adopted by the world’s leading manufacturers. Critical design and control criteria for the assembly process to ensure technical success are identified. The results of today’s adhesive applications are also discussed.

The trend toward part consolidation is leading to the bonding of large parts. While this simplifies the assembly process, it also increases the risk of failure. After all, almost every structural bonding operation involves parts that are large, expensive and responsible. If something goes wrong, the result can be costly or dangerous. Therefore, this article includes some considerations that are usually overlooked in other bonding situations.

From an industrial manufacturer’s point of view, the introduction of adhesive bonding into aerospace and all structural bonding has led to a general interest in the true capabilities of adhesives. In structural bonding, an adhesive is used that carries the full load of the structure. Very often the joints are also subjected to severe working conditions. Adhesives used in such cases, regardless of chemistry, must have the following properties:

Strength in the range of 10-35 MPa,
very high impact and peel strength, and
operate in a temperature range of -50 to 170°C.

Considering the above working conditions, special attention should be given to the selection of the right adhesive and durability tests.

Adhesive selection: a job for the engineer-designer

An engineer’s task of selecting an adhesive is like an awkward gauntlet of products and technologies. When engineers approach their first adhesive application, they typically try to gather as much information as possible about each type of adhesive and each chemistry. This is the wrong path and the wrong approach. It often leads to delayed production starts and process control problems.

A better way to design an assembly operation with adhesives is to review the expectations of the finished, assembled product and the operational constraints in the factory environment. This approach leads to defining joint durability expectations and manufacturing process requirements prior to substrate processing and adhesive selection. Defining these parameters in advance will clearly guide adhesive selection and limit the choice to a few chemistries (Figure 1).

Thinking about the sustainability of the connection

The most important issue in structural bonding is the durability of the bonded part. A single specimen does not answer the question of whether the bonded part will last 10 or 20 years in a working assembly. It is often true that adhesives that cause substrate failure in shear or peel tests fail completely in cyclic fatigue tests. Experience shows that simply testing overlap bonded specimens is a very poor indicator of long-term durability. In critical applications, it is better to perform repeated tests under expected loads, possibly with thermal cycling. Such a methodology is a far better indicator of the true durability of bonded joints, and a reputable adhesive supplier will be happy to assist with such testing.

When it comes to structural bonding, a critical requirement is to properly determine the requirements of the finished joint. Failure to fully understand the durability requirements is the number one cause of field failures observed by the author in the field. Here’s what to consider and how to properly investigate the following factors:

Working loads on the joint,
Type of stresses to be expected, i.e.: shear, impact, bending, etc,
Operating temperature range,
Cyclic thermal loads,
Impact and shock resistance,
Chemical resistance, and
Expected product life.

Technological parameters

Having defined the requirements for the durability of the bonded joint, the next step is to determine the process parameters for the bonding operation. Some points to consider are

The desired fixation time,
The required life time (mounting)
Bonding position, e.g. vertical or horizontal
Folding position and time,
Reaction method, i.e. heat, room temperature cure, etc,
Solvent system – aqueous, acetone, 100% solids, etc,
Adhesive rheology, i.e. should it be more liquid or more viscous?
Manual or automatic assembly,
Adhesive packaging – small, or feeding from bulk packaging (e.g., drum)
Dispensing equipment, one, two, three component,
Non-destructive testing of bond quality and adhesion, and
Transportation of parts.

Substrate Selection

Because the surface chemistry of the substrates to be bonded can affect the curing properties of many adhesives, it is best to leave the final selection of substrates to a time when the parameters of joint durability and manufacturing technology have already been defined. This is consistent with the philosophy of “design for manufacturing. A responsible engineer should make the selection of substrates and adhesives the result of defining prior requirements for joint durability and manufacturability. However, because such reasoning goes against the “common sense” favored by many engineers, the process too often is to select substrates and then build the concept of the bonding process around them.

Adhesive Selection: The Role of the Manufacturer (Supplier)

Once the durability requirements, process parameters, and substrate selection have been determined, it’s time to bring the adhesive manufacturer into the equation. The technical service department or a good distributor of almost any major adhesive manufacturer can usually provide a great deal of assistance at this stage. This can lead to the establishment of an industry-accepted test standard. Pitfalls in process parameters can also be identified. Because structural bonding depends so much on the condition of the substrate, the adhesive supplier usually (but not always – MB) can’t help with surface preparation, finishing and debris removal. Ultimately, any reputable company will be able to assist with bonding and test samples to demonstrate that the bonded joint meets the requirements.

Performance Standard

The next step in bonding implementation is to develop a written manual, a “production standard” that links process parameters, substrate specifications, and adhesive requirements. This step is often overlooked and is the key to continuous technology improvement. Problems can be solved by going back to this point where some parameters can be adjusted or changed and then written into an updated production standard.

Experience shows that serious problems arise when there is no production standard for the structural bonding process.

Case Study: Ford Car Bumpers

In 1986, Ford introduced a new model of the Taurus / Sable series. This series went down in history as the best-selling cars. The bumper design of this model used a completely new solution. The entire bumper consisted of a thermoplastic face and reinforcement beam bonded with reinforced methacrylate adhesive (Photo 1 and Figure 2). Determining the durability requirements and process parameters was critical to the choice of substrate and adhesive. Obviously, the bumper had to meet low-temperature impact requirements comparable to its metal counterparts. Ford’s long experience in defining bumper durability requirements added additional requirements, as did Federal Motor Vehicle Safety Standards (FMVSS) No. 215 for bumpers.

Durability requirements

Based on this experience, Ford determined that a structure using adhesive bonded substrates must achieve 80% of the control values after the following durability tests:

1000 hours at 88°C,
1000 hours at 38°C / 100% relative humidity
1000 hours at 54°C / water immersion
240 neutral salt spray cycles
80 Ford thermal cycles

Ford’s new bumper is made from the new Xenoy plastic manufactured by GE Plastic. This plastic is designed to be impact resistant, weather resistant, easy to paint and fully recyclable. It met all the durability requirements and was chosen for the job. One critical requirement was obvious: the bumper had to withstand a crash at -40°C at 8 km/h without failure. It was important for both the plastic and the adhesive to retain their energy absorption properties at this temperature without cracking. As a result, the Xenoy bumpers performed admirably, sustaining even less damage than their metal counterparts. To date, Ford has bonded more than 4 million thermoplastic bumpers with the reinforced methacrylate adhesive without a single failure during their service life.

Field Repair and Recycling

The history of Ford bumpers has highlighted two other issues that have led to increased interest and use of structural bonding. The first is the need for the bonding system to facilitate field repairs. Because structural bonding applications involve parts that are typically very large and valuable, the ability to repair them in the field is fundamental.

Second, more and more manufacturers, especially in the automotive industry, are choosing adhesive systems that can be recycled. This includes most thermoplastic adhesives and excludes most chemically cured adhesives. When an adhesive is recyclable, it means that the bonded part can be completely cut up and reshaped without costly and time-consuming cutting of the adhesive line from the recycled part. The methacrylate adhesives Ford chose to bond its thermoplastics meet both requirements.

Case Study: Vanguard’s Racing Sailboats

Vanguard manufactures high-end fiberglass racing sailboats for club and collegiate programs. The company’s most popular boat, the Club 420, went into production more than 20 years ago. Since then, more than 1,800 of these boats have been sold. They are used by every major school, university and yacht club in the United States. The boats are designed to withstand all the difficult situations caused by inexperienced boaters, such as collisions with a kaya or other boat, stranding (coming ashore – MB), and capsizing and sinking.

Patrick Muglia, production manager at Vanguard, explains: “We sell to the institutional market, our customers demand durability, some of these schools like Coast Guard and marine schools keep these boats in the water seven days a week. So they are constantly colliding, including with buoys during maneuvers.”

An analysis of customer observations and warranty repairs led to the conclusion that a disproportionate number were caused by installation with putty used to bond the hull to the deck and other fiberglass components. Over time, these putties became brittle and cracked, causing leaks and weakening the boat’s structure.

Before choosing an adhesive to replace the polyester putty, Vanguard asked us to compare the methacrylate polyurethane adhesives commonly used in yacht construction, as well as how they compare to a commonly used method such as bonding with a glass mat saturated with polyester resin (Figure 4).

Figure 4 shows a comparison of cyclic fatigue tests comparing both a marine polyurethane adhesive/sealant and a well-known methacrylate adhesive. The tests were performed under two different loading conditions. It is clear that polyurethane is not up to the task. It performs better as a sealant than as a structural adhesive.

Conversely, the methacrylate adhesive gives results that exceed the capabilities of polyester resin. How is this possible? The lightweight, flexible adhesive allows slight deformation, unlike a rigid resin, and the energy of the deformation is converted to heat.

Upon closer inspection, Vanguard found other problems with the previous production techniques using putty. Before applying putty, the entire surface to be bonded had to be thoroughly sanded or abraded to improve adhesion. This task is time-consuming, labor-intensive, and results in a high degree of scattering, which is also considered a normal feature of the technology.

Sanding produces fiberglass dust, which is harmful to health and causes illness by inhalation. For this reason, workers must wear safety goggles, dust masks, appropriate protective clothing and gloves while performing this operation. Note from Mr. Muglia: “People really hate this job. They have to change clothes, they sweat in those clothes, the goggles fog up… to tell you the truth, no one wants to do this job”.

Vanguard’s initial comparison yielded a financial result that they say will add $60 to the cost of building Club 420 boats. Mr. Chip Johns, President of Vanguard: “At first we just compared material costs. But that didn’t give us the whole picture. We gained labor savings, eliminated the sanding process and materials like sandpaper, and significantly reduced the cost of claims.

When they finished comparing costs, production efficiencies and warranty repairs, Vanguard was truly amazed. Despite the fact that methacrylate adhesives are much more expensive than polyester putties, overall production costs have definitely dropped.

Pat Muglia summed up his experience with adhesives this way: “Since we’ve been using structural adhesives in production, we’ve produced better quality boats, we’ve cut costs, people are happier, and I don’t have to worry about warranty repairs.

Chip John: “Our boats had a definite weakness – it was the bonding of the deck to the hull. The putty was the weak link in the whole system. Now that same joint is the strongest point in our design. The boat is as if it was made in one piece, which takes our product to a higher level of quality.

ISO 9000 and adhesive dispensing equipment

The philosophy of the ISO 9000 system is to continually build and improve the written standard that defines the entire structural assembly process. Describing each step in the actual assembly process, as well as specifying breaks for equipment maintenance, helps ensure that the job is done correctly. Many bonding operations also extensively involve the adhesive dispensing and application system. Inadequate equipment maintenance can result in a lack of repeatable bonding. One major boat manufacturer has taken the ISO 9000 philosophy to heart. Here, every adhesive dispensing machine has a maintenance action plan and a work card permanently attached to the machine. The benefits of ISO 9000 are tremendous when fully implemented in a bonding shop.

Adhesives Reduce Fugitive Emissions

Federal, state, and local laws regarding fugitive emissions are another challenge for manufacturers. Often, new adhesive technology can replace existing methods and reduce emissions. In another case study, a boat manufacturer reduced fugitive emissions by approximately 60% by introducing bonding of composite stringers in the assembly of liners. In this case, this represented a reduction in emissions of approximately two thousand kilograms per year.

Summary

The Ford bumper example illustrates the benefits of properly defining the required durability of an assembly based on structural bonding at the beginning of the manufacturing process. More than four million bumpers have been bonded without a single complaint or failure. The Vanguard example shows how durability requirements evolve over time. The use of polyester putty to bond the hull to the deck was appropriate 10 years ago. However, what was acceptable in the previous decade is a lower standard today. That’s why Vanguard re-evaluated the durability requirements for its boats and found that reinforced structural adhesives significantly improved this parameter. As Chip Jones noted, the project was successful because it focused on the durability expectations of the end product, not just the cost of materials.

Based on a paper presented at the Adhesives ’97 conference in Rosemont, M.Sc. Marek Bernaciak – Technical Consultant

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November 26, 2014

Adhesives simplify composite construction

Written by: Marek Bernaciak

Adhesives simplify composite construction

New MA adhesives for bonding plastics and metals

Introduction

Structural adhesives can help reduce emissions, increase assembly speed and improve productivity. The article explains how these adhesives have simplified the construction process in many composite applications in the architectural, transportation, marine and construction industries.

The use of structural adhesives has increased significantly over the last few decades. Among other things, these adhesives have been used to bond the Shuttle’s thermal shield tiles and have replaced mechanical fasteners in well-known bombers and stealth fighters. But what are structural adhesives? How do they simplify composite structures?

Simply put, ‘structural adhesives’ are those adhesives that, regardless of chemical structure, are used in load-bearing joints. Applications include the bonding of large or expensive parts, or joints where failure of the bonded joint could be very dangerous. The use of structural adhesives, particularly methacrylate structural adhesives, speeds up the manufacture of glass reinforced plastic (GRP) structures by allowing such parts to be bonded together without costly surface treatment or sandblasting. Labour costs are reduced and production is simplified.

Methacrylate adhesives

One of the major advantages of methacrylate adhesives is their ability to bond most materials with little or no surface preparation. In particular, methacrylate adhesives have a strong solvent action on almost all polyester resins and gelcoats. As a result, GRP parts made in open or closed moulds can usually be bonded without sanding or roughening.

Almost all resins can be successfully bonded. In the same way that methyl methacrylate monomer solvates polyester resin, it also solvates most of the waxes used in many other resins. On the other hand, if the parts are more than a few weeks old, some surface preparation may be required. In all cases, a laboratory test should be carried out to determine whether such preparation is necessary.

Architectural applications

The use of composite materials in architectural applications is growing rapidly. Architects are quickly learning that highly complex structures can be built quickly and easily from GRP. These structures are not only cost effective but also extremely durable.

The main consideration with such structures is how they are attached to the building. In general, this also means that such a structure can be attached to the building at a later date. The high strength and elongation of methacrylate adhesives give them the rigidity and durability to do this job. In addition, these adhesives work well in bonding materials with different coefficients of thermal expansion.

Bonding metal brackets

There are two important things to remember when gluing brackets to GRP. The first is to use toggle clamps to ensure the correct amount of pressure is applied as the glue cures. Secondly, the use of buttonholes provides a quick visual check that there is enough glue in the right place under the bracket.

When attaching metal brackets to composite structures, care must be taken to eliminate the ‘penetration’/transparency effect of the joint on the face. This effect can occur when the adhesive shrinks too much during curing, causing indentations on the face, and is particularly common when the laminate is very fresh or very thin. Fortunately, advances in adhesive technology have led to the development of new low-shrinkage adhesives that eliminate the penetration effect caused by adhesive shrinkage.

Figure 1. A slightly exaggerated diagram of a deformed aluminium profile bonded to a composite structure.

Stress and deformation of mismatched parts is another phenomenon that can also cause ‘voids’. Figure 1 shows a simple sketch of an aluminium reinforcement (actual application) whose curvature does not match the contour of the GRP part. Although the aluminium bracket is very rigid, the fitter presses the parts together in a clamp. Of course, once the glue had cured, the aluminium bracket returned to its original shape, causing the part to deform (Figure 2). As the assembly to be bonded was part of the façade of a large leisure centre, such play was unacceptable.

Figure 2. When glued together, the result is a concave surface that is aesthetically unacceptable.

Marine

The marine industry has been very quick to embrace the benefits of bonding. Applications that were typically done with glass mats (bonding structural components to resin and glass) are now routinely done with structural adhesives. The main advantage of structural adhesives in these applications is that they are faster and lighter than resin and glass. Another increasingly important advantage is the significantly reduced emissions of volatile organic compounds.

Figure 3 shows the hull of a 10 metre motor yacht after glue application. The deck is waiting above the hull to be lowered into place as soon as the workers have finished applying the adhesive. No expensive dispensing equipment is required for the application, as construction adhesives can be dispensed with most available dispensers. Photo 4 shows a worker using a simple plastic bag to dispense the mixed adhesive. The glue application time for a boat of this size is approximately 15 minutes.

There are two common types of deck to hull joints in boat building. Figure 5 shows a “knuckle-joint”, a pattern typical of Europe, Australia and New Zealand.

Figure 6 shows a joint known as a ‘shoe box joint’, which is more common in the USA.

From a technological point of view, a bolt joint may require additional time and material to produce sufficiently large flange surfaces for bonding. From an adhesive point of view, such a joint is superior to a ‘shoebox’ joint in every respect. Firstly, the horizontal surface of the flanges allows easier and more consistent application of adhesive by the installer. Secondly, a consistent thread of glue directly translates into a stronger and more leak-proof joint. Finally, the matching flat surfaces of the pin joint allow for easier alignment of the deck to the hull.

Once bonded, the joints can be shortened with bolts or riveted at regular intervals, depending on the manufacturer’s assumed design parameters and whether the boat is to be certified to Lloyds of London, Det Norske Veritas (DNV) or American Bureau of Shipping (ABS) requirements. In all cases the joint is covered by a bulwark railing).

Another construction technique that is increasingly being used in the marine industry is the use of stringers made entirely from GRP composites.

Figure 7.

For decades, boatbuilders had used plywood stringer systems as an internal framework to reinforce the hull and floor of the boat. Such systems were easy to make and very economical. On the other hand, water and moisture could attack wooden stringers and cause them to rot. In the age-old battle against seawater, many builders are now designing their stringers entirely from GRP composites. Despite the initial increase in tooling and material costs, the increased productivity and durability provide a very quick payback for builders. Studies show that gluing in GRP stringers increases bottom strength by 20 per cent and lateral strength by 10 per cent, without adding weight or labour.

Figure 8.

As well as the efficiency of gluing the stringers, customers and dealers also notice an improvement in quality. When you open the boot, you find a beautiful gelcoat room, not just a bare deck or old wood.

Transport applications

Today, many of the cabs of large trucks, their accommodation parts and fairings are made from GRP. The use of composite components is increasing as designers strive to make their trucks more aerodynamic. In addition, as interiors are designed to increase comfort for the driver, more GRP components are being used inside cabs for storage and rest (and entertainment) areas.

Figure 9.

Figure 9 shows the bonding of the stringer to the roof of the sleeper cab of a large truck. The stringer, which is glued to the roof, has flanges approximately 20 mm wide for gluing. The operator places the stringer on the roof and makes an outline of it with a red marker. He then applies glue to the inside of the roof and places the stringer in the correct position. A clamp is then used to hold the stringer in place for 80 to 90 minutes before the adhesive reaches its initial strength.

The use of structural methacrylate adhesive means that no sanding or roughening is required prior to bonding. In addition, adhesive application and assembly can be completed in less than half the time required for resin and glass mat bonding.

The benefits of structural bonding in large truck applications go beyond the elimination of simple surface preparation. The use of adhesives eliminates the need for fasteners such as rivets. Even today, most tractor trailers have metal panels joined by thousands of rivets. Each rivet creates a potential leak path through the cladding. The use of adhesives eliminates potential leaks and also creates an aesthetically pleasing appearance. In addition, where parts are made of GRP, adhesives reduce point loads, thus reducing potential cracking of the gelcoat.

Volatile organic compound (VOC) emissions

When composites are bonded using glass mat and resin, the amount of adhesive required is typically one third of the amount of resin.

Table 1.

Volatile Organic Compound (VOC) emissions for a general purpose styrene resin compared to a typical methacrylate adhesive

	Polyester resin	Methacrylate Adhesive
Quantity required	1500g	500g
Curing emissions	6% (styren)	1% (monomer MMA)
Calculation of emissions	1500 x 6% =	500g x 1% =
Net emissions	90g	5g

Table 1 shows the emission calculations for polyester resin and a typical methacrylate adhesive. It is clear from the table that emissions of volatile organic compounds can be reduced by more than 90%!

Simplified installation

The applications listed in this article show how structural adhesives can simplify assembly in composite structures.

The two marine applications shown – bonding the deck to the hull and bonding the stringers – are gaining increasing acceptance worldwide. Using methacrylate structural adhesives for these purposes allows boatbuilders to increase productivity without sacrificing quality.

In recent years, the construction of large truck cabins has evolved from a sheet metal flap fastened with thousands of rivets to the use of resin-glass composites (GRP) bonded with structural adhesives. The use of structural adhesives allows for faster assembly, reduced point loads on joints under load, and almost no translucency in the cab structure, bonnet or skin. In other words, the bonded part is stronger, more durable and more aesthetically pleasing.

Finally, the use of structural adhesives in place of polyester resins can also benefit the environment by reducing emissions of volatile organic compounds (VOCs) during composite assembly by up to more than 90%.

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November 26, 2014

Category: Articles

Compiled by: Slawomir Chorek

Bonding technique

Adhesion

Cohesion

Surface preparation for bonding

Examples of correct bonding

Direction of forces on bonded joints

Application methods for 2-part adhesives

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Written by: Aleksandra Lewandowska, Sławomir Chorek

MONOLITH – Leader in Structural Adhesives

Structural Adhesives – Definitions

Structural Adhesives Division

Comparison of structural adhesives and other material bonding methods

Principles of working with structural adhesives

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Written: Aleksandra Lewandowska, Sławomir Chorek

Metal bonding in the industrial sector

When are we going to glue?

The advantages

Bonding vs. other techniques

Adhesive selection factors

Adhesive types

How do you bond metals?

Reduced adhesive setting time

Summary

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Writting by: Katarzyna Gajda

Health and safety in the bonding process

Steps in the bonding process

Read the adhesive safety data sheet

Preparation of the bonding surface

Preparation of the adhesive

Application of adhesive

Joining the parts

Allow to cure time

Finishing the joint

Summary

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Written: Katarzyna Gajda, Sławomir Chorek

Design and construction of composite bonding

Composites

Advantages of composites

Composite bonding

How can composites be joined?

Disadvantages/weaknesses of bonding composites

Advantages / Strengths of composite bonding

What do I use to bond composites?

Advantages of methacrylate adhesives:

Disadvantages of Methacrylate Adhesives

Composite adhesives from our range

Epoxy Adhesives in Composite Bonding

Flexible adhesives (polyurethanes and MS polymers)

Summary

Bibliography

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Written by: Zygmunt Tyska

Hull bonding of laminate yachts

Yachts

PLEXUS adhesives in yacht bonding

An example of the use of PLEXUS adhesive for bonding a yacht hull

Working safely with PLEXUS adhesives

Advantages of PLEXUS Adhesives

Curiosity

Summary

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Written by: Sławomir Chorek, Marek Bernaciak

Flexible structural bonding

Purpose of MONOFLEX MS 611-1 adhesive:

Advantages of MONOFLEX MS 611-1:

Przeznaczenie kleju MONOLITH SE 131-1 i SE 132-1:

Benefits of MONOLITH SE 131-1 and 132-1 adhesives:

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