Sarah Vickers, Marketing and Product Manager at Oxford Advanced Surfaces, discusses the benefits and issues of water-based adhesives when bonding plastic or reinforced composite components.
With the legislative targets for greener vehicles, manufacturers in the automotive and other transport industries are investigating using lightweight materials as one approach to reducing emissions. Plastics and reinforced composites are increasingly being used to make components throughout the vehicle, but the bonding difficulties associated with these materials can cause a real headache for manufacturers. Mechanical fasteners add weight to the vehicle, clearly not ideal for lightweighting, so people look to adhesives for joining these substrates together.
A common way of bonding to plastics is to use solvent-based adhesives which swell the substrate surface and cause entanglement of the polymer chains. Aromatic hydrocarbons like ethyl benzene, xylene and toluene are common components in solvent based adhesives because they are effective at causing swelling on many, albeit not all, plastics. However the hazards that they pose to humans as well as to the environment are making them increasingly less welcome in manufacturing.
As a result, there is a drive towards using water-based adhesives that do not contain these harmful substances. However this leads to bonding issues because the primary adhesion mechanism to the plastic surface has been removed. This of course calls for some method of adhesion promotion.
Onto surface treatments provide a way of using water-based adhesives on plastics. OAS used its Onto EP1030 product to demonstrate how a water-based adhesive can be used to bond leather to a polyamide substrate. Without any adhesion promoter, the leather could easily be peeled away from the plastic. The Onto treatment boosted the adhesion to the extent that the leather actually tore before delamination occurred. The treatment is water/alcohol based and, like all of our products, contains no aromatic hydrocarbon solvents or chloropolyolefins.
Another benefit of water-based adhesives of course is that they are non-flammable, so OAS is currently developing a series of non-flammable adhesion promoters to complement these products.