Tackification Studies of Natural Rubber/Styrene-Butadiene Rubber Blends

Abstract

Abstract A 50:50 blend of NR and SBR 1011 is heterogeneous. When tackified with a resin which is compatible with the NR phase, but not the SBR phase, the resin appears to partition unequally between the NR and the SBR. The resulting heterogeneous pressure-sensitive adhesives exhibit very broad storage modulus transition zones. The increased breadth occurs predominantly at the lower frequency portion of the transition. This is quite different from the NR/SBR blends tackified with a resin which is compatible with both NR and SBR. The NR/SBR blend with compatible resins exhibits a single sharp transition which is similar in character to either pure NR or pure SBR adhesives prepared with completely compatible resins. The differences due to heterogeneity are clearly manifested in the mechanical properties of the blend and are reflected by the rolling ball tack and shear strength to steel properties. Rolling ball tack data are consistent with the hypothesis that the NR phase is more highly tackified than is the SBR phase. Shear adhesion to steel data further support this conclusion.