Preparation of skim natural rubber and polypropylene blends via melt blending: A study on physico-mechanical properties

High percentage of non-rubbers in Skim Natural Rubber (SNR) has restricted its use in manufacture of advanced rubber products. SNR were melt blended with polypropylene (PP) at different blend ratios to generate thermoplastic elastomers (TPEs). Standard Lanka Rubber (SLR) and PP blends were also prepared for the purpose of comparison. Tensile, hysteresis, hardness, water absorption, and dynamic mechanical properties of unvulcanized (UV) and dynamically vulcanized (DV) SNR/PP and SLR/PP blends were compared. Stress-strain behavior and TPE characteristics of both blends were similar. Tensile strength and modulus of SNR/PP blends decreased with the increase of SNR percentage. Elongation at break showed a decrease in UV blends and maxima at 50:50 blend ratio for DV blends. Dynamic vulcanization of the rubber phase improved tensile properties and hardness of the blends. Water absorption studies showed significantly higher equilibrium moisture content in SNR/PP blends, while difference in this property diminished with the increase of rubber phase. Water absorption and equilibrium moisture content decreased with dynamic vulcanization of rubber phase. Dynamic mechanical analysis confirmed multi-phase microstructure of the blends. Both blend systems showed similar dynamic mechanical properties and almost comparable thermo-mechanical properties confirming the potential of SNR as an alternative to SLR for selected applications.