Imagine if the letters on your keyboard faded away, the coating on your glasses came off or the numbers of your dashboard disappeared. This can happen if the manufacturer does not properly treat the plastic surface.
It is often necessary to print, coat or glue plastic materials as part of the manufacturing process. In order for liquid adhesives, glues, coatings or inks to adhere to the surface of moulded or extruded plastics, it is necessary to increase the surface energy to improve the surface wettability, thereby promoting stronger adhesion.
Corona & Plasma Surface Treatment
The polymer composition of plastics presents considerable challenges when designing materials that will bond with or decorate plastic. Surface treatment improves wettability by raising the material’s surface energy and improving the adhesive characteristics by creating bonding sites. The most advanced and successful methods of surface treatment are based on a principle of corona or plasma discharge through air or under vacuum.
Specialized corona and plasma systems treat almost everything from syringes to dashboards.
Surface energy
The phenomenon of surface energy is based on the relative energies of the solid substrate and the liquid in contact with it. Determining the surface energy of a polymer surface is critical to ensuring proper coating and print quality, as well as the adhesion properties – particularly important with the growing popularity of water-based inks, coatings, and adhesives.
Practical measurements of surface energy involve the interaction with a test liquid to determine wetting tension of solid materials as a measure of surface energy – a so called dyne test.
Tantec Corona and Plasma Treaters make things stick
Although there are numerous theories explaining the principles behind the process of corona and plasma treatment, the most commonly accepted theory appears to be the theory of high-speed oxidation. This theory states that the energy of the discharge breaks the molecular bonds on the surface of the non-polar substrate. The broken bonds then recombine with the free radicals in the discharge environment to form additional polar groups on the plastic surface. These polar groups have a strong chemical affinity to the polar inks, coatings and adhesives, resulting in improved adhesion. Similarly, this results in increased surface energy for the polarized surface, which correlates to improved wettability.