The influence of plasma treatment on the surface properties of high-performance thermoplastics

The plasma treatments, corona and low-pressure plasma, were applied to two so-called high-performance thermoplastics, polyetherimide (PEI), a liquid crystalline polymer (LCP) and, for comparison, to polypropylene (PP). The treated surfaces were characterized by surface energy studies. In addition, the shear strengths of aluminium-polymer joints using a range of different adhesives were measured. While for PP the changes in surface energy corresponded to the changes in shear strength, for PEI and LCP a clear correlation between pretreatment and adhesive strength could not be found. Different failure mechanisms occurred due to interaction of the plasma treatment with the morphological structure of both polymers, adhesive and plastic substrate. (Author)