A comparative study of the effect of degradation on the properties of PP/NR and PP/RR blends

The effect of various degradations on the tensile and morphological properties of polypropylene (PP)/natural rubber (NR) and PP/recycle rubber (RR) blends at different rubber content were studied. The blends were melt mixed using a Brabender Plasticorder torque rheometer at 190degreesC and 50 rpm. All blends were exposed at three different conditions, i.e., heated in oven (100degreesC) for 24 hrs, immersed in distilled water (90degreesC) for 24 hrs, and immersed in ASTM oil No. 3 for 70 hrs. The results indicated that at a similar rubber content and degradation condition, PP/RR blends exhibit a higher percentage of retention of tensile strength and Young's modulus but a lower elongation at break than PP/NR blends. Scanning electron microscopy (SEM) examination of the tensile fracture surface of PP/NR blends indicates a smooth fracture Surface than PP/RR blends after thermo-oxidative aging. This observation supports the higher retention of tensile strength after thermo-oxidative aging of PP/RR blends than PP/NR blends. Thermogravimetric analysis of both blends show that the thermal stability of PP/RR blends is higher than that of PP/NR blends.