Non-isothermal crystal nucleation of poly (L-lactic acid)
Non-isothermal crystal nucleation of poly (L-lactic acid)
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DOI：
10.1016/j.polymer.2015.11.006
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发表时间：
2015-12-16
期刊：
影响因子：
4.6
通讯作者：
Schick, Christoph
中科院分区：
文献类型：
--
作者：
Androsch, Rene;Iqbal, H. M. Naeem;Schick, Christoph
采用快速扫描芯片量热法对聚L-乳酸（PLLA）在非等温条件下的结晶成核动力学进行了分析，定量探讨了可结晶聚合物熔体冷却条件、晶核形成与冷结晶行为之间的关系。在1 ~ 1000 K·s（-1）的不同冷却速率下，PLLA的松弛熔体被玻璃化，这抑制了熔体结晶，但导致晶核的形成，这取决于冷却速率。然后根据Tammann的两阶段晶核发育法通过等温冷结晶动力学分析来探测冷却过程中形成的晶核的量。当以低于0.5 K s（-1）的速率冷却熔体时，仅发生摩尔质量为约100 kDa的PLLA的结晶，但已发现晶核以高达50 K s（-1）的速率形成。随着冷却速率在50和0.5 K s（-1）之间降低，晶核的数量增加，这随后增强了随后加热时的冷结晶，并且这延迟了玻璃退火期间额外晶核的形成并减少了额外晶核的量。(C)2015爱思唯尔有限公司版权所有。
The kinetics of crystal nucleation of poly(L-lactic acid) (PLLA) at non-isothermal conditions has been analyzed using fast scanning chip calorimetry, with this investigation serving as a concept study to quantitatively approach the link between the condition of cooling the melt of crystallizable polymers, the formation of crystal nuclei and the cold-crystallization behavior. The relaxed melt of PLLA has been vitrified by cooling at different rates between 1 and 1000 K s(-1), which suppressed melt-crystallization but led to formation of crystal nuclei depending on the cooling rate. The amount of nuclei formed during cooling was then probed by analysis of the kinetics of isothermal cold-crystallization according to Tammann's two-stage crystal nuclei development method. While crystallization of PLLA with a molar mass of about 100 kDa only occurs on cooling the melt at rates lower than 0.5 K s(-1), it has been found that crystal nuclei form at rates up to 50 K s(-1). With decreasing cooling rate between 50 and 0.5 K s(-1) the number of crystal nuclei increases which then enhances cold-crystallization on subsequent heating, and which delays the formation and reduces the amount of additional nuclei during annealing of the glass. (C) 2015 Elsevier Ltd. All rights reserved.