Modification of styrene–butadiene rubber surfaces by plasma chlorination

Abstract

Chlorination with halogenating agents in organic solutions is a common surface treatment for styrene–butadiene rubber materials to improve their adhesion to polyurethane adhesives. An attempt to replace this wet chemical method with a clean plasma technique has been undertaken. Styrene–butadiene rubbers (both model elastomers, such as Finaprene 435 and Finaprene 507 and a typical composite vulcanised rubber) were exposed to the action of plasma generated in various reactive mixtures containing chlorine moieties. As chlorine precursors, trichloromethane (CHCl 3), tetrachloromethane (CCl 4), and chlorine (Cl 2) were used. These compounds were supplied to the reactors as a pure agent or in a mixture with argon or oxygen. Pure argon and air were also tested. The process was performed both in RF (13.56 MHz) and AF (20 kHz) glow discharges, utilising electrode reactors working at low pressure. FTIR spectroscopy, contact angle measurements, and T-peel tests (before and after plasma treatment) characterised the elastomer surfaces. It has been found that for the pure CHCl 3 and CCl 4 plasmas with a relatively low power, the peel strength of the treated rubber surfaces is approximately 56% higher than that for the materials chemically chlorinated, and two to three times higher in comparison with the non-treated surfaces.