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.
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.
Contact Us
Please complete the form below and you will be contacted shortly.
For immediate technical assistance, please contact me on the following phone number:
601536440
