Isothermal and non-isothermal crystallization behavior of poly(l-lactic acid): Effects of stereocomplex as nucleating agent: [Polymer 47 (2006) 3826-3837]
Isothermal and non-isothermal crystallization behavior of poly(l-lactic acid): Effects of stereocomplex as nucleating agent: [Polymer 47 (2006) 3826-3837]
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DOI：
10.1016/j.polymer.2006.05.053
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发表时间：
2006-05
期刊：
影响因子：
4.6
通讯作者：
H. Tsuji;Hiroki Takai;S. Saha
中科院分区：
文献类型：
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作者：
H. Tsuji;Hiroki Takai;S. Saha
在聚乳酸（PDLA）含量为0.1 ~ 10wt%的范围内，研究了聚乳酸（PDLA）作为PLA立体复合物微晶对聚L-乳酸（PLLA）等温和非等温结晶行为的影响。在从熔体等温结晶中，PLLA球晶的半径生长速率（结晶温度（Tc）≥125°C）、PLLA球晶形成的诱导期（ti）（Tc≥125°C）、PLLA微晶的生长机制（90°C≤Tc≤150°C）以及PLLA膜的机械性能不受PDLA的掺入或立体复合物微晶作为成核剂的存在的影响。与此相反，立体复合物微晶的存在下显着增加PLLA球晶的数量每单位面积或体积。在熔体等温结晶中，在PDLA含量为10wt%时，由于PLLA球晶数量的增加，PLLA整体结晶的开始、一半和结束时间（分别为tc（S）、tc（1/2）和tc（E））比PDLA含量为0wt%时的那些短得多。当PDLA含量为0.1wt%时，tc（S）、tc（1/2）和tc（E）均比PDLA含量为0wt%时的大，可能是由于球晶数目减少和球晶长度增加所致。这似乎是由游离的PDLA链引起的，其没有形成立体复合物微晶。另一方面，在0.3- 3wt%的PDLA含量下，对于低于95°C和高于125°C的Tcran范围，tc（S）、tc（1/2）和tc（E）短于或类似于在0wt%的PDLA含量下的那些，而对于100-120°C的Tcran范围，该倾向相反。在从熔体冷却期间的铸态或非晶制得的PLLA膜的非等温结晶中，添加高于1wt%的PDLA有效地加速了PLLA的整体结晶。X射线衍射分析表明，当PDLA含量大于1wt%时，PLLA薄膜中形成了立体复合物。该研究表明，当仔细选择PDLA含量和结晶条件时，加入少量的PDLA可有效地加速PLLA的整体结晶。
The effects of incorporated poly(d-lactic acid) (PDLA) as poly(lactic acid) (PLA) stereocomplex crystallites on the isothermal and non-isothermal crystallization behavior of poly(l-lactic acid) (PLLA) from the melt were investigated for a wide PDLA contents from 0.1 to 10wt%. In isothermal crystallization from the melt, the radius growth rate of PLLA spherulites (crystallization temperature (Tc)≥125°C), the induction period for PLLA spherulite formation (ti) (Tc≥125°C), the growth mechanism of PLLA crystallites (90°C≤Tc≤150°C), and the mechanical properties of the PLLA films were not affected by the incorporation of PDLA or the presence of stereocomplex crystallites as a nucleating agent. In contrast, the presence of stereocomplex crystallites significantly increased the number of PLLA spherulites per unit area or volume. In isothermal crystallization from the melt, at PDLA content of 10wt%, the starting, half, and ending times for overall PLLA crystallization (tc(S), tc(1/2), and tc(E), respectively) were much shorter than those at PDLA content of 0wt%, due to the increased number of PLLA spherulites. Reversely, at PDLA content of 0.1wt%, the tc(S), tc(1/2), and tc(E) were longer than or similar to those at PDLA content of 0wt%, probably due to the long tiand the decreased number of spherulites. This seems to have been caused by free PDLA chains, which did not form stereocomplex crystallites. On the other hand, at PDLA contents of 0.3–3wt%, the tc(S), tc(1/2), and tc(E) were shorter than or similar to those at PDLA content of 0wt% for the Tcrange below 95°C and above 125°C, whereas this inclination was reversed for the Tcrange of 100–120°C. In the non-isothermal crystallization of as-cast or amorphous-made PLLA films during cooling from the melt, the addition of PDLA above 1wt% was effective to accelerate overall PLLA crystallization. The X-ray diffractometry could trace the formation of stereocomplex crystallites in the melt-quenched PLLA films at PDLA contents above 1wt%. This study revealed that the addition of small amounts of PDLA is effective to accelerate overall PLLA crystallization when the PDLA content and crystallization conditions are scrupulously selected.