Biodegradable silica rubber core-shell nanoparticles and their stereocomplex for efficient PLA toughening
Biodegradable silica rubber core-shell nanoparticles and their stereocomplex for efficient PLA toughening
复制标题
DOI：
10.1016/j.compscitech.2018.02.026
复制
发表时间：
2018-05-03
影响因子：
9.1
通讯作者：
He, Chaobin
中科院分区：
文献类型：
--
作者：
Li, Zibiao;Muiruri, Joseph K.;He, Chaobin
为了克服可再生聚乳酸聚乳酸易碎和机械稳定性差的缺点，提高可再生聚乳酸聚乳酸相对于传统石油基热塑性塑料的竞争优势，采用顺序开环聚合（ROP）法制备了可有效增韧聚乳酸的硅橡胶核壳纳米颗粒。设计了以二氧化硅为内核，P（CL-mLA）为“橡胶”中间层，末端PDLA链（SiO2-r-PDLA）为核壳结构，便于与PLLA基体形成立体配合物，增强界面控制。采用溶液共混-注射成型法制备了PLLA/SiO2-rPDLA纳米复合材料。核磁共振（H-1 NMR和C-13 NMR）结果证实了二氧化硅颗粒表面接枝“橡胶”链和PDLA链的存在。此外，通过差示扫描量热法（DSC）和拉伸测试，PLLA/SiO2-r-PDLA纳米复合材料的热性能和力学性能均有显著改善。除了在纳米复合材料中形成立体配合物外，对这些立体配合物纳米复合材料的熔融稳定性的详细研究表明，当橡胶段存在时，这些立体配合物具有“记忆”立体配合物行为，即在熔体再结晶后具有完美重组的能力（熔体记忆效应）。最后，利用扫描电镜（SEM）和小角x射线散射（SAXS）对结构变形机理进行了研究。从SAXS上可以清楚地观察到裂纹，而扫描电镜显示纤维化结构。因此，裂纹和纤颤是PLLA/SiO2-r-PDLA体系的关键变形机制。这些令人兴奋的新型填料为PLA高级复合材料的应用开辟了新的领域。(C) 2018年Elsevier Ltd.出版
In the effort to overcome the shortcomings such as brittleness and poor mechanical stability, and increase the competitive edge of renewable poly(lactic acid) PLA over conventional petroleum-based thermoplastics, silica rubber core-shell nanoparticles for effective PLA toughening were successfully synthesized by sequential ring opening polymerization (ROP). The core-shell structure was designed with silica as inner core, P(CL-mLA) as 'rubber' middle layer and terminal PDLA chains (SiO2-r-PDLA), to facilitate the stereocomplex formation with PLLA matrix for enhanced interface control. The PLLA/SiO2-rPDLA nanocomposites were fabricated through solution blending-injection molding process. Nuclear magnetic resonance (H-1 NMR and C-13 NMR) results confirmed the presence of grafted 'rubber' and PDLA chains from the surface of silica particle. In addition, PLLA/SiO2-r-PDLA nanocomposites showed tremendous improvement in thermal and mechanical properties using differential scanning calorimetry (DSC) and tensile testing, respectively. Besides the formation of stereocomplex in the nanocomposites, a detailed study on the melt stability of these stereocomplex nanocomposites revealed a 'memorized' stereocomplex behavior, i.e., having the ability to perfectly reassemble after re-crystallization from melt (melt memory effect), when rubber segment is present. Finally, structure-deformation mechanisms were studied using scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS). From SAXS, crazing was clearly observed whereas SEM revealed fibrillated structures. Thus, crazing and fibrillation are the key deformation mechanisms in PLLA/SiO2-r-PDLA system. The exciting new fillers could open up new horizons for PLA advanced composites applications. (C) 2018 Published by Elsevier Ltd.