Melting behavior and crystallization kinetics of starch and poly(lactic acid) composites

Differential scanning calorimetry was used to characterize the melting behavior and isothermal crystallization kinetics of pure poly(lactic acid) (PLA) and blends of PLA with various corn starch contents at varying isothermal crystallization temperatures (90-125degreesC). The experimental data were evaluated using the well-known Avrami kinetic model. The Avrami exponent, constant, half-time of crystallization, and degree of crystallinity were obtained. Talc, a nucleating agent, was also blended with PLA at 1% by volume (v/v) as a comparison. Starch effectively increased the crystallization rate of PLA, even at a 1% content, but the effect was less than that of talc. The crystallization rate of PLA increased slightly as the starch content in the blend was increased from 1 to 40%. An additional crystallization of PLA was observed, and it affected the melting point and degree of crystallinity of PLA. (C) 2003 Wiley Periodicals, Inc.