Elimination of the reactivation process in the adhesion of chlorinated SBS rubber with polychloroprene adhesives

Chlorination treatment of a thermoplastic styrene-butadiene-styrene rubber (SBS) with a 3 wt% solution of trichloroisocyanuric acid (TCI) in methyl ethyl ketone (MEK) introduces chlorinated and oxidized moieties on the rubber surface which increase its surface energy and produces surface microroughness. Consequently adhesion properties, evaluated by T-peel strength measurements in chlorinated SBS/solvent based-polyurethane adhesive/leather joints, are enhanced. In this study, two solvent-based polychloroprene adhesives (PCP0 and PCP30R) have been considered as an alternative to the commonly used solvent-based polyurethane adhesive (PU). A thermoreactive phenolic resin was added to one of the polychloroprene adhesive formulations (PCP30R). This tackifier resin favors chlorination of the adhesive and reinforces the interface between the chlorinated adhesive and the chlorinated rubber surface. Besides, PCP30R adhesive does not need adhesive reactivation and considerable high T-peel strength value (5.7 +/- 0.3 kN/m) was obtained. Elimination of the reactivation process implies a considerable improvement of the manufacturing process in the footwear industry.