| Abstract: | Compounded polypropylene powders with various concentrations of corn starch were processed in a Haake torque rheometer at constant temperature, 180 °C, for different times in a closed system. A scanning electron micrograph of 5‐min processed sample shows a fine dispersion of starch particles in the polypropylene (PP) matrix. A good distribution and interaction of the starch particles are seen with increasing processing time (up to 15 min). Infrared spectroscopy evidence on the extracted films shows that most interactions between PP and starch are obtained after about 10 min processing. The presence of 2–6 wt% starch in the PP has a melt‐stabilising effect by reducing melt flow index and increasing apparent viscosity with a good correlation. However, 6 wt% starch gives complete inhibition of the PP melt degradation up to 20 min processing. Carbonyl groups are not formed during processing of PP containing 6 wt% starch. This is also an indication of a starch stabilising effect on the PP chemical structure. An increase in elongation at break of PP films having 6 wt% starch, when compared with the controls, is observed, while their ultimate tensile strength remains almost the same. © 1999 Society of Chemical Industry |
