Micromechanical characterisation of plasma treated polymer surfaces

It has been recently demonstrated that a physically thick (about 50 nm) int erfacial region ('interphase') is formed between a plasma deposited film an d the underlying plasma treated or untreated polymer substrate. This can ha ve an important effect on the performance of optical coatings, protective c oatings, barrier films for packaging, and others. In the present work we st udy the effect of N-2 and He plasma treatment of polycarbonate on the surfa ce and near-surface (composite) mechanical properties. Multi-technique mech anical testing (scratching and depth-sensing indentation) has been performe d using a broad range of applied loads (1 mN-10 N). We demonstrate that low -load scratching provides a more surface-specific information on the hardne ss and scratch resistance than do other methods. We also point out the adva ntage of constant-load, multipass scratching compared to the progressive-lo ad approach. (C) 1999 Elsevier Science S.A. All rights reserved.