Enhanced crystallization of poly(lactide) stereocomplex by xylan propionate

• Published in: Polymer international 2016-03, Vol.65 (3), p.339-345
• Main Authors: Ishii, Daisuke, Kimishima, Misaki, Otake, Katsuto, Iwata, Tadahisa
• Format: Article
• Language: English
• Subjects: Blending; Blends; Crystallinity; Crystallization; Melt blending; Melt blends; Methyl alcohol; nucleating agent; poly(lactide) stereocomplex; Stereocomplexes; xylan propionate
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.5061

Enhancement of stereocomplex crystallization in poly(lactide) stereocomplex (scPLA) was accomplished by isothermal crystallization after melt blending of scPLA and xylan propionate (XylPr). The effect of xylan propionate (XylPr) as a novel biomass‐derived nucleating agent on the poly(lactide) sterecomplex was investigated. Addition of XylPr to an enantiomeric blend of poly(l‐lactide) (PLLA) and poly(d‐lactide) (PDLA) was performed in either the solution state or molten state. The solution blend of PLLA/PDLA with XylPr was prepared by mixing equal volumes of 1 wt% XylPr/PLLA and 1 wt% XylPr/PDLA solutions in chloroform and precipitating in methanol. The solution blend with XylPr showed shorter half‐time crystallization than the solution blend without XylPr in isothermal crystallization between 80 and 140 °C, although homocrystallization occurred. Enhanced stereocomplex crystallization in the solution blend with XylPr was observed at 180 °C, where no crystallization occurred in the solution blend without XylPr. Addition of XylPr to PLLA/PDLA blend in the molten state was performed at 240 °C. Thereafter, the melt blend of PLLA/PDLA with or without XylPr was either quenched in iced water or isothermally crystallized directly from the melt. Isothermal crystallization of the melt‐quenched blend with XylPr gave a similar result to the solution blend with XylPr. In contrast, the melt‐crystallized blend with XylPr formed only stereocomplex crystals after crystallization above 140 °C. Furthermore, the melt‐crystallized blend with XylPr showed a higher crystallinity index and melting temperature than the melt‐crystallized blend without XylPr. This shows that XylPr promotes stereocomplex crystallization only when the blend of PLLA/PDLA with XylPr is directly crystallized from the molten state just after blending. © 2016 Society of Chemical Industry