Degradability of expanded starch/PVA blends prepared using calcium carbonate as the expanding inhibitor



In this study, expanded starch/poly(vinyl alcohol) (PVA) blends for packing material were prepared by using calcium carbonate as the expansion inhibitor to investigate the degradability and the structural and mechanical properties of expanded starch/PVA/calcium carbonate blends (ESPCs). The structure of ESPCs became more compact with increasing CaCO3 content and at least 2 parts of CaCO3 were required to obtain the sufficient inhibiting effect on the expansion. As CaCO3 content increased from 1 to 4 parts, tensile strength more than doubled from 70 to 180 KPa, while elongation at break increased about 1.5-fold. The moduli of ESPCs also increased with increasing CaCO3 content, but they decreased continuously with exposure to UV radiation over all periods of exposure and remained in the range of 10–15 KPa after exposure for 7 weeks. The weight loss of ESPCs due to exposure to soil environment increased with exposure time and the final weight loss after the 5-week exposure was about 25–30%. Specifically, the degradability of ESPC with 20 parts of PVA was 5% higher than that of ESPC with 30 parts of PVA. The water solubility of ESPC with 30 parts of PVA was somewhat higher than that of ESPC with 20 parts of PVA. Furthermore, most of ESPCs began to be degraded thermally at 292°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 911–919, 2004