Crystallization behavior and morphology of polylactic acid (PLA) with aromatic sulfonate derivative

This article provides a detailed investigation of crystallization behavior and morphology of polylactic acid (PLA) in the presence of a nucleating agent: potassium salt of 5-dimethyl sulfoisothalate, an aromatic sulfonate derivative (Lak-301). Isothermal crystallization kinetics of PLA melt mixed with Lak at concentrations of 0.25-1 wt % was investigated at a range of crystallization temperature, 140-150 degrees C. To gain further insight on the effect of Lak, nonisothermal differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized optical microscope (POM), heat deflection temperature (HDT), and rheology were also performed. At 0.25 wt % Lak, crystallinity of PLA increased from 10% to 45%, and in 1 wt % Lak, maximum crystallinity of 50% was achieved. With 1 wt % Lak, crystallization half time reduced to 1.8 min from 61 min for neat PLA at 140 degrees C. The isothermal crystallization kinetics was analyzed using Avrami model. Values of the Avrami exponent for PLA with Lak were mainly in the range of 3 indicating a three dimensional crystal growth is favored. Crystallization rate was found to increase with increase in Lak content. Observation from POM confirmed that the presence of Lak in the PLA matrix significantly increased the nucleation density. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43673.