EFFECTS OF BLEND RATIO AND SBR TYPE ON PROPERTIES OF SILICA-FILLED SBR/NR TIRE TREAD COMPOUNDS

ABSTRACT The influences of blend ratio between SBR and NR and SBR type, emulsion SBR (E-SBR) and solution SBR (S-SBR), on properties of silica-filled passenger car tire tread–based compounds were investigated. Results reveal that, with increasing NR proportion, cure time and most mechanical and dynamic properties, for example, tensile strength, tear strength, modulus, abrasion resistance, and wet skid resistance of the compounds and vulcanizates, are reduced, whereas the improvements in elongation at break and crack growth resistance are observed. The unexpectedly impaired mechanical and dynamic properties identified in the presence of NR are mainly caused by thermal degradation of NR taking place during the mixing process at high temperature. Compared with E-SBR, S-SBR provides superior properties in many aspects, that is, higher modulus and greater abrasion and wet skid resistances as well as lower heat buildup and rolling resistance. However, E-SBR gives greater tear strength than S-SBR.