Poor Adhesion (Surface Energy)
Non-stick may be a great feature for ensuring your food doesn’t stick to the pan, but it’s certainly not a good thing for the adhesive industry. We have all experienced the frustration of trying to bond something, only to find that the glue has peeled off or the substrate has fallen off. However, fret not as here at Forgeway we enjoy a challenge.
When it comes to bonding with an adhesive, there is one key factor which can determine whether you will have a strong or a weak bond between the adhesive and the substrate. This determining factor is surface energy, which can be thought of as a willingness to bond. Each material has a different surface energy, for example glass and metal have high surface energies whereas plastics such as PTFE and PE have very low surface energies.
For an adhesive to be successful it must be able to flow out and make intimate contact with the substrate, this is referred to as “wetting out” the surface. When an adhesive is placed on a substrate if the adhesive has a higher surface energy than the substrate, it will not ‘wet out’ effectively. Another way of thinking about this is to imagine a child in a toy shop, if the toy shop has lots of toys (high surface energy) the child will grab hold of the toys and not want to leave. However, if the toy shop is empty (low surface energy) the child will have nothing to grasp and will quickly walk out.
At Forgeway we can carry out Dyne testing to determine the surface energy of your substrate and give advice and recommend products to ensure you get a strong bond. One way of increasing the surface energy of a substrate is to use our Formoa surface activator. However, there are other ways of increasing the surface energy such as plasma and corona surface treatment.
So, when it comes to bonding plastics or difficult substrates, its crucial you consider surface energy and take the necessary precautions to ensure you achieve a strong bond. For more advice don’t hesitate to call or see page 41 of The Fundamentals of Adhesives.