Studies on blends of natural rubber and ethylene propylene diene rubber modified with phosphorylated cardanol prepolymer: Processability, physico-mechanical properties, and morphology

Abstract

The melt processability and physico-mechanical properties of blends of natural rubber (NR) and ethylene propylene diene rubber (EPDM) containing different dosages (0-10 phr) of phosphorylated cardanol prepolymer (PCP) were studied in unfilled and china-clay-filled mixes. The plasticizing effect of PCP in the blends was evidenced by progressive reduction in power consumption of the mixing and activation energy for melt flow with an increase in the dosage of PCP. The PCP-modified blend vulcanizates showed higher tensile properties and tear strength despite a decrease in the chemical crosslink density (CLD) index. This is presumably due to the formation of a crosslinked network structure of PCP with the rubbers and improved dispersion of the filler particles in the rubber matrix, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermogravimetric analysis showed an increase in thermal stability of the blend vulcanizate in presence of 5 phr of PCP.