Mehrabi Mazidi Majid, Sharifi Hossein, Razavi Aghjeh Mir Karim, Zare Leila, Khonakdar Hossein Ali, Reuter Uta
Faculty of Polymer Engineering, Sahand University of Technology, Sahand New Town, Tabriz 51335-1996, Iran.
Department of Materials Science and Engineering, Sharif University of Technology, Tehran 1458889694, Iran.
ACS Appl Mater Interfaces. 2023 May 10;15(18):22445-22470. doi: 10.1021/acsami.2c21722. Epub 2023 Apr 28.
Super-tough poly(lactic acid)/polycarbonate (PLA/PC) (50/50) blends with an excellent balance of stiffness, toughness, and thermal stability were systematically designed and characterized. Poly(methyl methacrylate) (PMMA) was utilized as a novel, highly effective nonreactive interphase to promote PLA-PC phase compatibility. Partial miscibility of PMMA with both PLA and PC produced strong molecular entanglements across the PLA-PC phase boundary followed by an excellent phase adhesion. This was predicted from interfacial energy measurements and supported by dynamic mechanical thermal analysis, morphological observations, and mechanical tests. Ternary PLA/PC/PMMA blends exhibited an exceptional set of stiffness, tensile and flexural strength, tensile and flexural ductility, and thermal stability together with improved impact strength compared with neat PLA and uncompatibilized PLA/PC blends. Addition of nonreactive polybutadiene--styrene--acrylonitrile (PB--SAN) impact modifier to the compatibilized blend resulted in further dramatic improvements in the dispersion state of PC and PMMA phase domains followed by the development of an interconnected structure of PC, PMMA, and PB--SAN domains in the PLA matrix. Such a network-like morphology, with rubbery particles percolated at the interface between the dispersed structures and surrounding PLA matrix, produced a tremendous increase in impact resistance (≈700 J/m) and tensile ductility (≈200% strain) while maintaining excellent stiffness (≥2.1 GPa). The combined effects of interfacial localization of impact modifier particles, network-like morphology (extended over the entire volume of the blend), and strong phase interactions between the components (due to mutual miscibility) are described to be responsible for super-tough behavior. The role of PMMA as an efficient interphase adhesion promoter in the toughened quaternary blends is also clarified. Impact fractography revealed multiple void formations, plastic growth of microvoids, and the formation of void-fibrillar structures around as well as inside the dispersed structures as the main micromechanical deformation processes responsible for massive shear yielding and plastic deformation of blends. Blends designed in this work offer remarkable improvements in tensile and flexural ductility, impact resistance, and heat deflection temperature compared with neat PLA resin. The overall characteristics of these blend systems are comparable and/or superior to those of several commercial thermoplastic resins.
系统地设计并表征了具有优异刚度、韧性和热稳定性平衡的超韧性聚乳酸/聚碳酸酯（PLA/PC）（50/50）共混物。聚甲基丙烯酸甲酯（PMMA）被用作一种新型的、高效的非反应性界面层，以促进PLA-PC相的相容性。PMMA与PLA和PC的部分互溶性在PLA-PC相界处产生了强烈的分子缠结，进而具有优异的相粘附性。这是通过界面能测量预测的，并得到动态机械热分析、形态观察和力学测试的支持。与纯PLA和未增容的PLA/PC共混物相比，三元PLA/PC/PMMA共混物表现出一组特殊的刚度、拉伸和弯曲强度、拉伸和弯曲延展性、热稳定性以及提高的冲击强度。向增容共混物中添加非反应性聚丁二烯-苯乙烯-丙烯腈（PB-SAN）抗冲改性剂，导致PC和PMMA相畴的分散状态进一步显著改善，随后在PLA基体中形成PC、PMMA和PB-SAN畴的互连结构。这种网络状形态，橡胶颗粒渗透在分散结构与周围PLA基体之间的界面处，在保持优异刚度（≥2.1 GPa）的同时，使抗冲击性（≈700 J/m）和拉伸延展性（≈200%应变）大幅提高。据描述，抗冲改性剂颗粒的界面定位、网络状形态（扩展到共混物的整个体积）以及组分之间强烈的相相互作用（由于相互混溶性）的综合作用导致了超韧性行为。还阐明了PMMA在增韧四元共混物中作为有效界面粘附促进剂的作用。冲击断口分析表明，多个空洞形成、微空洞的塑性生长以及在分散结构周围和内部形成空洞-纤维状结构是导致共混物大量剪切屈服和塑性变形的主要微观力学变形过程。与纯PLA树脂相比，本工作中设计的共混物在拉伸和弯曲延展性、抗冲击性和热变形温度方面有显著提高。这些共混体系的总体特性与几种商业热塑性树脂相当和/或更优。
