CHEMICALLY MODIFIED EMULSION SBR IN TIRE TREADS

A series of Emulsion SBRs (E-SBR) with polar and nonpolar third co-monomers are studied in silica filled compounds. The applied third co-monomers include polar types such as acrylonitrile (ACN), hydroxypropyl methacrylate (HPMA) and I-vinylpyridine (VP) and nonpolar types such as isoprene and 1,3-pentadiene. The impact of the third comonomers on compound reinforcement, hysteresis, abradability and viscoelastic properties is studied for single polymer compounds as well as polymer blends with 1,4-cis-polybutadiene (cis-BR) and Natural Rubber (NR). Changes in miscibility of the polymer blends are studied via viscoelastic temperature sweeps and via Atomic Force Microscopy (AFM). All blends show a miscibility behavior in agreement with Hildebrand solubility parameter predictions. The nonpolar comonomers lead to an increased miscibility while the polar co-monomers reduce the miscibility with cis-BR and NR. These changes only show up in blend Tg's and viscoelastic response and stay associated with a heterogeneous AFM blend structure with different degrees of mixed phase compositions. The impact of the third co-monomers is more pronounced in the case of cis-BR than in the case of NR blends in this study. The preferred chemically modified ESBR is the one with 3% HPMA showing improved performance relative to unmodified ESBR and unmodified Solution SBR (SSBR).