Ultrasonic cleaning of SBR rubber to improve the performance of subsequent plasma torch treatment

Paraffin wax and other moieties in sulfur vulcanized styrene-butadiene rubber formulations may migrate to the surface, reducing the adhesive strength in joints produced with polyurethane adhesive. In this study, with the aim to remove paraffin wax and other anti-adhesion moieties on the rubber surface to improve adhesion, prior to plasma torch treatment, a methyl ethyl ketone (MEK) cleaning in an ultrasonic bath has been carried out. The surface modifications produced on the rubber surface have been analyzed by contact angle measurements, ATR-IR spectroscopy, XPS and SEM. The adhesion properties have been evaluated by T-peel strength of treated rubber/polyurethane adhesive joints. Ultrasonic cleaning in MEK resulted in partial removal of paraffin wax on the rubber surface and, thus, lower contact angle values, decreased relative intensity of the infrared bands due to hydrocarbon moieties and lower percentage of carbon assessed from XPS spectroscopy were obtained. The ultrasonic cleaning in MEK of the rubber increased the effectiveness of the atmospheric pressure plasma torch treatment, and surface oxidation was produced. However, the oxidation degree decreased with time after plasma torch treatment, likely due to ageing of the surface treated rubber.