Solvent-based adhesives are found in consumer glues, but are also used in industrial settings. You may be exposed to them if you work in printing, textiles, or any kind of manufacturing environment. It is important to know the dangers of solvents and the precautions to take when working around them, but first you should understand what they are and how they are made.
A solvent-based adhesive is a glue or adhesion product that is usually available in the form of a liquid. Water-, oil-, and low-boiling gasoline-based adhesives are the most common — liquids are usually quite viscous to make it easier for them to dry, while aerosol-packaged solutions are very popular due to their quick-dry function.
The logic behind solvent-based adhesives is that containing an adhesive inside a more malleable or spreadable substance will make it easier to apply. This allows users to be more thorough when applying the adhesive, reaching areas that would be difficult to cover with a solid glue. A more thorough coating of adhesive will ensure effective performance.
Solvent-based adhesives are produced when an adhesive material is blended with a suitable solvent to create an adhesive polymer solution. This is not a simple process, as some polymers are effectively incompatible with certain solvents — the most effective solvent-based adhesives will be produced using a polymer with a stable molecular structure that complements the chosen solvent.
A polymer (synthetic or natural) is dissolved in a solvent, usually either liquid or low-boiling gasoline product, to produce a polymer solution. The polymer can take a great deal of time to dissolve, depending on the stability of the polymer and the corrosive qualities/temperature of the solvent solution. Great care is taken not to accelerate the process, as this can destabilise the chemicals leading to an ineffective bonding process as well as potentially dangerous by-products.
Resins are dissolved in a solvent to produce a tacky polymer solution, which can be extremely adhesive when dry, as well as acting as a thermal insulator. Most commercial solvent-based adhesives will also contain inhibitors to stop them setting in the tube, as well as accelerators that react on exposure to moisture and light to reduce drying times.
Most general-purpose adhesives will be included in this bracket, which makes water solvents the most commonly used glue product in the household and classroom. They were originally produced using natural compounds such as cellulose, rubber latex, and starch, but can now be developed using synthetic materials such as polyvinyl acetate (PVA), which will improve the adhesive qualities of the eventual compound.
Organic solvents are used to dissolve or extract materials. The drying time of the adhesive tends to be far quicker than that of a water solvent, as the faster evaporation of the solvent allows the glue and any additives to be concentrated and exposed to set. Organic solvents can be a much more effective in an adhesive formulation than a water solvent, but have been the subject of concern given their toxicity and association with environmental issues like global warming.
When solvent-based adhesives are applied, the polymer solution is effectively allowed to dry quickly as the solvent evaporates. The time this takes will vary based on what sort of adhesive solution you are using, and the solvent used in the formulation. The solution needs to be given time for the solvent element to evaporate, leaving only the glue-like substance behind. For an aerosol can this may happen in a matter of seconds, but for a liquid-based adhesive this can take some time, depending on the surface and the environment. After the solvent evaporates, the glue will become stronger until there is no solvent left in the solution, and the adhesive reaches its maximum effectiveness.
Water-solvent adhesives are generally not as permanent or as quick to dry as organic solvents. As long as the glue has not dried, it is possible to remove any unwanted spills of a water-based adhesive with warm water — some types are even soluble in water after they have dried. They are generally very easy to spread and have no corrosive qualities, so can be used on any material without a chemical reaction — though they will only be effective on certain materials.
The strongest of the organic solvent adhesives will dissolve materials, effectively welding them together as the glue dries. Many organic solvents are designed to work with specific materials, due to the molecular structure of the adhesive compound. For example, a PVC cement will only work when applied to PVC. Application to any other materials, including clothing, can cause major problems. This applies to many different types of organic solvents and great care should be taken to ensure that you aren’t applying the wrong type of adhesive to your material, as discussed in the next section.
As important as it is to choose an appropriate adhesive, preparing the surface is key. It isn’t simply a case of wiping the area of dust before applying the adhesive, as many surfaces will have several layers of dirt and materials that will prevent an adhesive from working correctly. We would recommend giving the surface a wipe clear of any dust or debris before applying a degreaser to rid the surface of traces of oil or grease. Finally, the surface should be abraded to remove any flecks of paint or old adhesive. This can be done using a fine-grain sandpaper or possibly steel wool.
Due to the range of chemicals used in solvent-based adhesives, it is important to check whether this adhesive is the most appropriate to use in the circumstances. Water solvents are great in that they are easy to use, aren’t dangerous and can be semi-permanent if you only require temporary sticking. Organic solvents, however, are much stronger and are structured using water-resistant bonds — these often have sufficient flexibility to enable them to join together materials such as fabric or leather. These adhesives can be unstable however, and applying the solution to certain materials could cause volatile chemical reactions, which will not only damage the material but could cause you harm.
Due to its natural resistance, paper is one of the easiest materials to stick. Paper can be fragile though, and susceptible to being damaged if the wrong type of glue is used.
Plastic can be difficult to stick due to its low resistance and the potential of an adverse chemical reaction if the wrong type of glue is used.
Wood also benefits from having a high amount of resistance, so sticking isn’t too difficult. Due to the density of wood, however, a strong glue should be chosen to counteract the gravitational force. A solvent-based adhesive will usually be the most appropriate to use for wood, due to its strong adhesive qualities.
Metal can generally be a difficult material to stick due to its high density and shiny surface. In addition, the practical application for sticking metal suggests it will be expected to be strong, sturdy and durable — this will require an effective hold.
When it comes to solvent-based adhesives, safety should be of a paramount importance. It is essential to know what the best practice is when working with these adhesives, and whether eye or mouth protection should be worn to stop inhaling fumes or irritating skin. Organic solvents can be particularly dangerous if the correct safety measures aren’t adhered to, especially in environments with children (such as schools).
As a general rule, water-based adhesives are fairly safe and therefore ideal for use in school environments. The only real issues associated with the use of water-based adhesives is if the user is allergic to a material in the compound, most commonly latex, as this can cause irritation to the skin and the eyes. Starch pastes, such as wallpaper paste, are the only water solvent to contain a potentially harmful substance, as fungicides are added to prevent fungi or spores growing in damp conditions.
Organic solvents can present a number of dangers to the user, the first of which being that nearly all organic solvents are highly flammable. For this reason, these solvents should never be used in an environment where they can easily come into contact with a naked flame. As well as being highly flammable, they should also not be applied directly to fabric or materials that will later be exposed to a naked flame, as there is a possibility that the material will retain its flammable properties. Always use in a well-ventilated room.
While it may seem quite obvious, organic solvents are dangerous, which can present a number of problems if they come into contact with the skin. Some solvents may cause irritation to the skin, particularly if they are left on for a long time. There is also the risk that the organic solvent can be absorbed through the skin. There is also the probability that the glue will remain on the skin and be difficult to remove, or even glue something else to the skin. In this case (depending on where the glue is on your body), the glue spillage should be cleaned with warm water as soon as possible, and medical attention sought if the glue retains its hold. The problem here is that as solvent-based adhesives are designed to be as water-resistant as possible, they don’t tend to dissolve in water unless they have just been applied.
You should also be sure to keep the room well-ventilated when using organic solvents, as inhaling the vapour can cause dizziness, sickness, and breathing problems. Inhalation of this vapour can be addictive, and the serious effects that it will have on the brain mean that great care should be taken to prevent any inhalation. You may even consider a face mask if you are working in close contact with a solvent-based adhesive solution throughout the day.
With a liquid glue comes the risk of accidental spillages, and the irreversible damage they can cause to clothing and other materials. Protective clothing should be worn when using solvent-based adhesives if the user anticipates any risk of spillage, while surfaces should also be covered in a disposable material such as newspaper or clear plastic.
The fluid nature of water-solvent adhesives makes the risk of spillage very real. These types of glue can be quite easy to clean up however, as long as you catch them before they dry. Sponging the spillage with cold water before it dries should be enough to save the material from the adhesive, but if you have used a weather-proof or waterproof compound, you may face a struggle. Once the glue is dry, you will face a struggle removing it, and it will almost certainly damage the materials if you do manage to unstick them.
For organic solvents, it isn’t as simple as trying to dissolve the glue in water, as this will often have no effect. The only effective way to remove organic-solvent adhesives is to use a similar solvent to that used in the original glue compound — this can be extremely difficult given that a lot of these solvents are not widely available, due to the dangers associated with them.
You must be very careful when attempting to remove these types of adhesive in case the two solvents end up reacting with each other. It isn’t the case of simply purchasing over-the-counter cleaners, as there is a huge variation between nail varnish remover, paint stripper, and leather cleaner — all possible solvents that can be used to remove glue.
You may find when purchasing an adhesive that major brands stock removal solutions. They are generally a lot more expensive than buying the solvent on its own, but the convenience of the purchase is probably worth the additional expenditure. At least this way you can be sure that you are purchasing the right removal solution for the job. Buying this in foresight of spillages could be an excellent decision.
Solvent-based adhesives should be stored in a cool, dry place with the lid securely attached, out of reach of children and animals. Never store organic solvents, particularly those in aerosol cans, within range of a naked flame or a source of heat.
The temperature of the room in which the adhesive is stored can seriously affect the longevity of the product. If you know that you’re looking to use the adhesive again within the few days, don’t waste your time packing it away in the shed — try covering it tightly and storing it in the fridge. The cold temperature stops the glue from hardening, you just need to be sure that it doesn’t leak onto the rest of your refrigerated items.
Please check the packaging of your solvent-based adhesive for any specific safety or application advice, and feel free to contact us if you have any additional questions about adhesives or any of our chemical products.