Rheological and mechanical characterization of poly(lactic acid)/polypropylene polymer blends

Poly(lactic acid) (PLA) was melt blended with polypropylene (PP) with the aim of replacing commodity polymers in future applications. Since cost of PLA is quite high, it is not economically feasible to use it alone for day to day use as a packaging material without blending. This paper reports the preparation of poly(lactic acid)/polypropylene polymer blends (PLA/PP) using a laboratory scale single screw extruder. Rheological and mechanical properties of the prepared blends were determined. The rheological experiments were carried out on a capillary rheometer, the effect of shear rate, temperature and PLA content on the flow activation energy and true viscosity of the blends were described. Mechanical properties of the blends were investigated on dog bone-shaped samples obtained by injection molding; tensile tests were performed using Testometric M350-10KN. The effect of PLA content on Young's modulus, strain at break and stress at break of the blends were described. The rheological results showed that the true viscosity of the blends is between that of the pure polymers, whereas the flow activation energy of the blends is less than that of the pure polymers. The mechanical results showed incompatibility between PLA and PP in the blend.