Study of two types of styrene butadiene rubber in tire tread compounds

The ratio of vinyl butadiene and styrene groups in styrene butadiene rubber (SBR) structures is a crucial factor that affects the inherent rubber char acteristics such as glass transition temperature, T-g, hysteresis, strength , etc. In this paper, two types of SBR (Krynol 1721 and Buna VSL 5025-1) wh ich contain higher ratios of these two groups, were blended with natural ru bber (SMR 5) and compared with a blend of general purpose SBR (Krynol 1712) and SMR 5. The results show that the blends with the two rubbers possess a markedly lower resilience (i.e. higher hysteresis) than that of the genera l purpose SBR. Besides resilience, other properties of the compounds, Moone y viscosity, scorch time, cure time, tensile strength, tear strength, and a geing resistance were also investigated. At a similar blending ratio of 50: 50, blends with Krynol 1721 and Buna VSL 5025-1 show markedly lower rebound resilience while other mechanical properties are considered acceptable. Th is preliminary investigation indicates that the two rubbers are suitable fo r wet grip improvement, Subsequently, the ratio of Krynol 1721 and Buna VSL 5025-1 in the blends was varied from 30 to 70 phr. As the ratio of the rub bers is increased, a reduction in rebound resilience is also observed and t he effect of Buna VSL 5025-1 is more pronounced than Krynol 1721. The resul t is consistent with the higher T-g of the former. Mooney viscosity, scorch time, cure time and ageing index (based on tensile strength) are increased but there is a slight drop in tensile strength and tear strength. (C) 2001 Elsevier Science Ltd. All rights reserved.