Time resolved study of oriented crystallisation of poly(lactic acid) during rapid tensile deformation
Time resolved study of oriented crystallisation of poly(lactic acid) during rapid tensile deformation
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DOI：
10.1016/j.polymer.2005.05.081
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发表时间：
2005-07-25
期刊：
影响因子：
4.6
通讯作者：
Fuller, W
中科院分区：
文献类型：
--
作者：
Mahendrasingam, A;Blundell, DJ;Fuller, W
具有 4% D-乳酸共聚单体的聚（L-乳酸）在 80、90、100、110 和 120 C 下以 4 s(-1) 的拉伸速率以无定形状态拉伸，同时以 0.12 s 的间隔记录 WAXS 和 SAXS 图案。在 80、90 和 100 C 下，结晶非常快（1-4 s(-1)），并遵循一级转变过程，得到高度取向的晶体。尽管结晶度接近 0.2，但在这些温度下几乎检测不到 SAXS 图案。在 110 和 120 摄氏度下，结晶非常缓慢（类似于 0.01 s(-1)），并产生取向度较低的晶体。最终在 120 摄氏度下结晶后，形成两点 SAXS 图案并具有狭窄的横向扩展，表明“烤肉串”形态。当 80 摄氏度拉制的样品在 120 摄氏度退火时，会形成很强的四点 SAXS 图案。较高拉制温度下拉制和结晶行为的变化归因于链收缩弛豫过程的开始。退火后的WAXS纤维图案显示中间层线上的采样与具有10(3)螺旋的a晶型一致。然而，在退火之前，采样表明存在不同的、不太明确的螺旋结构。 (c) 2005 Elsevier Ltd. 保留所有权利。
Poly(L-lactic acid) with 4% D-lactic acid comonomer has been drawn in the amorphous state at 80, 90, 100, 110 and 120 C at an extension rate of 4 s(-1) while simultaneously recording WAXS and SAXS patterns at intervals of 0.12 s. At 80, 90 and 100 C, crystallisation is very rapid (1-4 s(-1)) and follows a first order transformation process to give highly oriented crystals. SAXS patterns were barely detectable at these temperatures despite fractional crystallinity of similar to 0.2. At 110 and 120 degrees C, crystallisation was very slow (similar to 0.01 s(-1)) and gave rise to crystals with a lower degree of orientation. After eventual crystallisation at 120 degrees C, a two-point SAXS pattern develops with narrow lateral spread, suggesting `shish kebab' morphology. When the 80 degrees C drawn sample was annealed at 120 degrees C, a strong four point SAXS pattern develops. The change in drawing and crystallisation behaviour at higher draw temperature is attributed to the onset of chain retraction relaxation processes. The WAXS fibre pattern after annealing shows sampling on intermediate layer lines that is consistent with the a crystal form with a 10(3) helix. However, prior to annealing, sampling indicates a different, less defined helical configuration. (c) 2005 Elsevier Ltd. All rights reserved.