COMPARATIVE STUDY OF PLASMA-THIOPHENE AND-ACETYLENE COATED SILICA IN SBR AND EPDM REINFORCEMENT

摘要

The surface characteristics of silica were modified by plasma-thiophene and -acetylene film deposition. The plasma-coated fillers were blended with S-SBR and EPDM, and their influence on the final vulcanizate properties was compared with untreated silica and silanized silica.The change in the surface energy of plasma-acetylene (PA) and thiophene- (PTh) coated silica was characterized by immersion tests in liquids of various surface tension, water penetration measurements, Thermo Gravimetric Analysis (TGA) and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS). All techniques gave evidence of a polymeric PA- and PTh-film deposition on the surface of silica. The properties of S-SBR and EPDM, filled with untreated, PA- , PTh- and silane-treated silica, were investigated by measurement of the Payne effect, bound rubber content and weight loss related to bound rubber, the reinforcement parameter, relative ranking of cross-link density and mechanical properties. The results show a lower degree of flocculation for PTh-silica filled EPDM due to a better match of the surface energies compared to untreated and PA-treated silica. EPDM filled with plasma-thiophene coated silica shows the lowest reinforcement parameter value, thus improved dispersion compared to untreated, silane-treated and plasma-acetylene silica. However, PA-silica filled EPDM shows better mechanical properties compared to untreated and plasma-thiophene coated silica. The PTh-silica filled S-SBR shows a higher bound rubber content, which results in better mechanical properties of the S-SBR compound compared to the one with PA-coated silica.The overall results show that the compatibility and interaction of silica with different rubbers can be controlled by tailoring the surface energy of the filler by plasma-polymerization. The different functionalities on the silica surface result in different levels of compatibility and interaction, as well as final vulcanizates properties.