Xylan esters as bio-based nucleating agents for poly (L-lactic acid)

Xylan esters of varying alkyl chain lengths (C2-C12) were screened for their effect on the crystallization of poly(L-lactic acid) (PLEA). Among the xylan esters, only xylan propionate (XylPr) and xylan butyrate (XylBu) exhibited a nucleating effect on PLEA during non-isothermal crystallization. Blending of 1% XylPr or XylBu with PLEA led to a decrease in the crystallization temperature (T-c) of PLEA from 125 degrees C to 96 or 97 degrees C, respectively. Similar results were also obtained for 0.1% blends of the same ester. Isothermal crystallization studies revealed that the PLEA blends exhibited faster crystallization rates, higher crystallinities and smaller spherulites than neat PLEA. Consequently, the PLEA blends possessed lower degrees of haze than neat PLEA and their thermal expansion values were also lower than that of neat PLEA when heated above their glass transition temperature (60 degrees C), indicating their resistance to heat deformation. The mechanism of nucleation was proposed based from the WAXD analysis results. (C) 2013 Elsevier Ltd. All rights reserved.