Effect of fillers on mechanical properties of dynamically crosslinked styrene butadiene rubber/high density polyethylene blends

The effect of fillers on the mechanical properties such as stress-strain behavior, tensile strength, percentage strain at-break, Young's modulus and tear strength have been investigated. Different filled crosslinked thermoplastic elastomers of styrene butadiene rubber (SBR)/high density polyethylene blends (HDPE) blends were prepared using silica, HAF-carbon black, china clay and TiO2. The extent of polymer-filler interaction has been analyzed by Kraus as well as Cunneen-Russell equation. The reinforcement ability of the filler was increased in the order of silica > HAF-black > clay > TiO2. The nature of the filler and filler loading has a dramatic effect on the mechanical properties of SBR/HDPE blends. Filled blends showed improved mechanical properties such as enhanced of strain at-break, when fillers are incorporated. The initial trend of properties for all filled system is the enhancement of properties. When HAF-black is used as the filler, at higher loading strain at- break is found to decrease due to the stiffness of the matrix. In the case of clay, there is a deterioration of properties occurs on higher loading, which is attributed to dilution effect and all TiO2 filled system have lower elongation at break than the base polymer. Theoretical models namely Guith's and Kerner's model have been compared with the experimental values of Young's modulus of filled system. The experimental values of modulus are found to be higher than the theoretical values indicating strong interaction between the filler and the matrix. SEM studies of the tensile and tear fractured surfaces, of the filled blends have been carried out. The variation in properties was correlated with the morphology of the system.