Effect of electrodeless glow discharge on polymers

Abstract

The effects of gas plasma generated by electrodeless (inductive coupling) glow discharge on polymers were investigated as functions of gas pressure, discharge power, exposure time, and type of plasma gas. A remarkable similarity between the plasma susceptibilities of low molecular weight organic compounds and polymers was observed; i.e., polymers which have ether, carbonyl, ester, or carboxylic acid attached to a nonaromatic structure are very susceptible to plasma. The weight loss was proportional to the exposure time and exposed area. The discharge power and type of gas were found to have a great influence on both the rate of weight loss and the morphology of the exposed surface. The predominant effect of plasma on polymers was found to be degradation (manifested by weight loss). The crosslinking effect was found to be marginal with many polymers; however, significant crosslinking was observed with double bond-containing polymers. The crosslinking was examined by swelling the treated films. With copolymers of styrene–butadiene, 4-vinylpyridine–butadiene, methacrylic acid-butadiene, and acrylic acid–butadiene, the crosslinking was greatly dependent on the discharge power, the butadiene content of the copolymers, and the exposure time. Both degradation and crosslinking by gas plasma were generally limited to the exposed surface; however, the propagation of crosslinking in the direction of thickness was observed with copolymers of styrene–butadiene. The plasma of organic vapor also cause degradation of plasma-susceptible polymers, particularly at high wattage, although the deposition of polymer occurs simultaneously.