Study on phase transition behavior and lamellar orientation of uniaxially stretched poly(L-lactide) / cellulose nanocrystal-graft-poly(D-lactide) blend
Study on phase transition behavior and lamellar orientation of uniaxially stretched poly(L-lactide) / cellulose nanocrystal-graft-poly(D-lactide) blend
复制标题
单轴拉伸聚(L-丙交酯)/纤维素纳米晶-接枝-聚(D-丙交酯)共混物的相变行为和层状取向研究
DOI：
10.1016/j.polymer.2018.07.036
复制
发表时间：
2018
期刊：
影响因子：
4.6
通讯作者：
Zhang Jianming
中科院分区：
文献类型：
--
作者：
Nagarajan Selvaraj;Hu Jian;Wu Hao;Duan Yongxin;Zhang Jianming
随着高性能绿色复合材料的发展，表面功能化纤维素纳米晶（CNC）作为增强体沿着生物高分子材料得到了广泛的应用。在我们的前期工作中，已经证明CNC接枝PDLA（CNC-g-PDLA）可以通过PLLA/PDLA立体复合物的相互作用提高PLLA基质的结晶成核密度和热分散能力。在此，为了理解CNC-g-PDLA对PLLA/CNC-g-PDLA纳米复合材料的变形行为的作用，将熔融淬火的PLLA/CNC-g-PDLA纳米复合材料在160 °C下以各种拉伸比单轴拉伸。拉伸的PLLA/CNC-g-PDLA复合材料允许我们区分复合材料中的三个单独组分的晶体转变和晶体取向，即（i）PLLA基质，（ii）PLLA/PDLA立体复合物作为界面相存在，和（iii）CNC增强体。结果表明，在拉伸过程的初始阶段，出现了PLLA α′和PLLA/PDLA立体复合物（βC）晶体。随着拉伸比的增加，无序α′逐渐向有序α和β相转变，而β C相在整个拉伸过程中基本保持不变。对各种晶体取向函数的计算表明，α型片晶沿拉伸轴的取向度最大，取向度为沿着轴。同时，CNC纳米颗粒与β C晶体在拉伸过程中形成纳米尺度的串晶结构，并呈现出相对较低的取向。该研究为制备具有分级结晶和取向结构的高性能聚乳酸纳米复合材料提供了物理指导。
Towards the development of high-performance green composites, the surface functionalized cellulose nanocrystals (CNC) have been widely used as reinforcement along with biopolymer. In our previous work, it has been demonstrated that CNC grafted with PDLA (CNC-g-PDLA) could improve the crystal nucleation density and heat distraction ability of PLLA matrix via the PLLA/PDLA stereocomplex interaction. Herein, to understand the role of CNC-g-PDLA on the deformation behavior of PLLA/CNC-g-PDLA nanocomposites, the melt-quenched PLLA/CNC-g-PDLA nanocomposite was uniaxially stretched at 160 °C with various draw ratios. The stretched PLLA/CNC-g-PDLA composites allow us to discriminate the crystal transformation and crystal orientation of three individual components in the composites, that is, (i) PLLA matrix, (ii) PLLA/PDLA stereocomplex existed as interfacial phase, and (iii) CNC reinforcement. The results indicate that PLLA α′ and PLLA/PDLA stereocomplex crystals (βC) appear at the initial stage of drawing process. The disordered α′ transforms to ordered α and β forms gradually with increasing in draw ratio, whereas βC-crystals keep almost unchanged during the whole drawing process. The calculation on orientation function of various crystals suggests that the lamellaes of α form have the largest orientation degree along the stretching axis. Meanwhile,CNC nanoparticles and the βCcrystals form the nano-dimensional shish kebab structure during stretching and present relatively low orientation. This study provides the physical insight to guide the preparation of high performance PLLA nanocomposites with hierarchical crystal and orientation structure.