Influence of Dispersoid Particle Size on the Morphology and Mechanical Properties of Natural Rubber With Island‐Nanomatrix Structure

ABSTRACT The influence of the dispersoid particle size variation on the morphological characteristics and mechanical properties of natural rubber (NR) with polystyrene island‐nanomatrix structure was investigated in this study. Fresh NR latex was incubated with urea and then processed through a series of centrifugation and redispersion steps at different forces to fractionate it into four low protein NR (LPNR) with average diameters of 238, 492, 721, and 1102 nm. Subsequently, graft copolymerization of styrene onto LPNR particles was carried out in the latex stage to prepare the NR with a polystyrene island‐nanomatrix structure. The relationship among particle size, morphology, and mechanical properties of the graft copolymer was analyzed. Transmission electron microscopy observations confirmed the formation of polystyrene island‐nanomatrix structure in each graft copolymer and revealed that the compactness of nanomatrix network increased as NR particle size decreased. The effect of nanomatrix network compactness on the mechanical properties was investigated through measurements of tensile properties, tear resistance properties, and viscoelastic properties, supported by digital image correlation strain mapping technology. A higher nanomatrix compactness was found to enhance mechanical properties and result in a more homogeneous distribution of strain.