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Study on biodegradable polymer materials based on poly(lactic acid). I. Chain extending of low molecular weight poly(lactic acid) with methylenediphenyl diisocyanate
Author(s) -
Zhong Wei,
Ge Jinjie,
Gu Zhenyu,
Li Wenjun,
Chen Xin,
Zang Yi,
Yang Yuliang
Publication year - 1999
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19991205)74:10<2546::aid-app24>3.0.co;2-z
Subject(s) - prepolymer , crystallinity , polymer , polymer chemistry , condensation polymer , materials science , lactic acid , glass transition , molar mass distribution , crystallization , chemical engineering , chemistry , polyurethane , organic chemistry , composite material , biology , bacteria , engineering , genetics
Methylenediphenyl diisocyanate (MDI) was used as the chain extender for low molecular weight poly(lactic acid) (PLA) to produce high molecular weight biodegradable polymer material with a better heat resistance. PLA prepolymer with a number‐average molecular weight ( M n ) of 5800 and a weight‐average molecular weight ( M w ) of 9800 was produced by direct polycondensation using stannous octoate as the catalyst. After 40 min of chain extension at 175°C, the resulting polymer had a M n of 15,000 and a M w of 57,000. The glass transition temperature ( T g ) of the low molecular weight PLA prepolymer was 48.6°C. After chain extension, the T g of the resulting polymer was raised to 67.9°C, as determined by DSC. DMA results also indicate that the heat resistance was improved by the chain extension. The DSC spectrum and X‐ray diffraction pattern of annealed samples showed that both the crystallinity and rate of crystallization of PLA were lowered by chain‐extension reaction due to the formation of branched molecular structure. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2546–2551, 1999