Investigating the effect of the thermal component of atmospheric plasmas on commodity polymers

Atmospheric pressure non-equilibrium plasma (APNEP) has been developed in t he UK by EA Technology Ltd and is currently being investigated in a joint p roject with the University of Surrey. APNEP has been used to induce surface modification changes on commodity polymers such as high density polyethyle ne (HDPE), low density polyethylene (LDPE), polypropylene (PP), poly(ethyle ne terephthalate) (PET) and poly(methyl methacrylate) (PMMA). A stable atmospheric pressure glow discharge can be formed with a variety o f gases, (e.g., nitrogen, air, argon and helium). In all cases, the plasmas are capable of inducing surface modification of commodity polymers in the near-field and remote afterglow regions. However, as APNEP can have a signi ficant thermal component, care must be taken to avoid thermal decomposition of the polymers. This study has used differential scanning calorimetry (DSC) and thermogravi metric analysis (TGA) to investigate the thermally induced transitions and thermal decomposition behaviour of commercial polymers. The DSC measurement s give melting points, heats of fusion and crystallinities. TGA has been us ed to measure the onset of thermal degradation in both air and nitrogen atm ospheres. In parallel with these experiments, temperature profiles of the d ownstream region of APNEP have been recorded. As a result, positioning of s amples and residence times to avoid thermal damage to the substrates can no w be achieved. (C) 1999 Elsevier Science B.V. All rights reserved.