کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5204521 1381964 2006 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Effects of molecular weight and small amounts of d-lactide units on hydrolytic degradation of poly(l-lactic acid)s
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Effects of molecular weight and small amounts of d-lactide units on hydrolytic degradation of poly(l-lactic acid)s
چکیده انگلیسی

Films of poly(l-lactic acid) (PLLA) with different number-average molecular weights (Mn) and d-lactide unit contents (Xd) were made amorphous and the effects of molecular weight and small amounts of d-lactide units on the hydrolytic degradation behavior in phosphate-buffered solution at 37 °C of PLLA were investigated. The degraded films were investigated using gravimetry, gel permeation chromatography, polarimetry, differential scanning calorimetry, X-ray diffractometry, and tensile testing. To exclude the effects of crystallinity on the hydrolytic degradation, the films were made amorphous by melt-quenching. The incorporation of small amounts of d-lactide units drastically enhanced the hydrolytic degradation of PLLA. In the period of 0-32 weeks, the hydrolytic degradation rate constant (k) of PLLA films increased with increasing Xd, while the k values did not depend on Mn. This means that the effects of Xd on the hydrolytic degradation rate of the films are higher than those of Mn. In contrast, in the period of 32-60 weeks neither Xd nor Mn was a crucial parameter to determine k values, probably because in addition to these parameters the differences in the amount of catalytic oligomers accumulated in films and crystallinity affect the hydrolytic degradation behavior of the films. The initially amorphous PLLA films remained amorphous even after the hydrolytic degradation for 60 weeks.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer Degradation and Stability - Volume 91, Issue 8, August 2006, Pages 1665-1673
نویسندگان
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