Plastics and composites are commonly used in the manufacture of engineered products as a result of their favourable properties like light weight, flexibility and chemical resistance, but the solvent and heat resistance exhibited by many of these materials can make them extremely difficult to bond to. This means that if a plastic component needs to be painted, coated or joined with adhesive then the surface of the substrate must be treated first to avoid bond failure at the interface.
One way of preparing plastic surfaces is to use chemical adhesion promoters. Most adhesion promoters for plastics contain aromatic hydrocarbons like toluene, xylene or ethyl benzene as well as a functional additive. The solvents swell the plastic surface to cause entanglement of the functional polymer chains with the substrate, creating a primed surface that is then compatible for bonding or coating.
But aromatic hydrocarbons are a source of concern for manufacturers in terms of health, safety and environment, and many people are now looking for alternatives. In addition to solvents, many of these adhesion promoters contain chloropolyolefins which cause recycling issues at the end of product life due to their slow degradation.
On some substrates these adhesion promoters are not effective enough to meet the bonding requirements that are required for product performance, and an alternative is needed if the same substrate is to be used for production. Fortunately OAS has a solution.
We have designed a series of chemical surface treatments that promote adhesion to plastics and plastic composite substrates without the use of harmful aromatic hydrocarbons. Based on our proprietary technology, Onto™ Highly Reactive Chemistry, the mechanism of adhesion promotion does not rely on solvent disrupting the surface and is effective on even the most inert substrates. Instead, heating the treatment causes a chemical reaction, bonding the treatment permanently to the surface. Many of our treatments are waterbased which means that VOCs are reduced, and we are working towards non-flammable, low-VOC versions of our treatments.
This is good news for manufacturers – a solution with no aromatic hydrocarbons means a safer working environment for employees and a more environmentally friendly production process. This is particularly good news for automotive manufacturers that are looking to decrease the level of emissions released during production, helping to bring them in line with current legislative targets in air quality.