Effect of processing on the melt degradation of starch-filled polypropylene

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

Influence of compatibilizer on blends degradation during processing

“…Torque values for blends were roughly between the torque values for PP and PS. We observe for all cases a torque reduction as a function of processing time, as expected due to thermomechanical degradation of polypropylene [52] and polystyrene [27,53] . The values of torque after loading (10 minutes), the values of torque in 90 minutes and the variation between 10 and 90 minutes of experiment are summarized in Table 1.…”

Effect of photo‐initiators on melt degradation of polypropylene and starch‐filled polymer

“…A comparison between these data with those in Fig 1 (a–c) at 0.5 wt% of the PIs indicates that the presence of starch in the pp matrix brings stability to the polymer 6. 15 Corn starch does not accelerate thermal oxidation of the pp, but rather acts as a heat stabiliser. This can be explained by the effect of some additives on its composition and thermal barrier action of the starch 18.…”

“…A stabilising effect of corn starch on thermo‐oxidation of low‐density polyethylene has recently been reported 6. It has also been found that addition of 6 wt% corn starch to pp prevents polymer degradation completely during melt processing of the blend 15…”

Recent advances in starch, polyvinyl alcohol based polymer blends, nanocomposites and their biodegradability

“…Starch can also be used as a filler to produce reinforced plastics (Bagheri, 1999;Evangelista, Nikolov, Sung, Jane, & Gelina, 1991). Usually, a small amount of starch (6-30%) was compounded with synthetic polymer, increasing the products' biodegradability.…”