生物质聚羟基脂肪酸酯纤维及其扭转拉伸诱导结晶研究

Polyhydroxyalkanoates (PHAs) is a kind of green, environmental-friendly ,biodegradable and renewable polymeric materials synthesized by microorganisms. However, their developing prospects are limited by poor heat resistance in processing, weak melt strength, slow crystallization rate and the low fiber toughness. In this project, the chemical structures, melt strength and crystallization kinetics of PHAs are regulated through molecular chain structure design and the induction of twist-draw process. And the focus of this project are studying the effects of PHAs’ chemical structure on heat-resistance, linear viscoelasticity, crystalline structure and crystallization kinetics, which reveals the inducing relationships of reverse stretching position and stretching technique on oriented crystallization process of fibers, and tracks the evolution laws of service behavior and fiber structure. Also, in this project, better thermal stability, high nucleate temperature and fast crystallization rate bio-based fibers were fabricated, and mechanism of realizing molecular chain microbeam twisting by reverse-stretch was clarified. In conclusion, this project, not only offers a new way to developbiomass PHAs fiber, a new idea of building high-strength bio-based fibers, but also promotes the development about intersection of polymer chemistry, condensed matter physics and engineering disciplines, which broadens the application field of bio-based polyester fibers.

聚羟基脂肪酸酯(PHAs)是一类由微生物合成的可降解高分子材料，具有绿色、环保、可再生的优点，但同时存在加工耐热性差、熔体强度低、结晶速率慢和纤维脆性大的问题。本项目拟从化学结构设计和扭转拉伸外场诱导两方面调控PHAs的化学结构、熔体强度和结晶动力学。重点研究化学结构对PHAs耐热性、线性黏弹性、结晶结构和结晶动力学的影响，揭示扭转拉伸位置和拉伸工艺对纤维结晶取向的诱导关系，跟踪并研究生物质纤维的服役行为及其结构演变规律。项目最终制备一种集高热稳定性、高成核温度、快结晶速率等性能为一体的生物基新材料，探索发明一种扭转拉伸诱导生物基纤维结晶的新方法，阐明扭转拉伸实现 “分子链微束加捻”的机理。本项目的开展，不仅为开发生物质PHAs纤维提供新的方法、为构建高强度生物基纤维打开新的思路，还能促进高分子化学、凝聚态物理学、工程学等学科的交叉发展，扩宽生物质聚酯的应用范围。

本项目针对生物基PHBV纤维熔纺过程中存在的成核活化能低、结晶速率慢、初生纤维易粘连、纤维强度低等难题，通过结晶异相成核、长链支化结构设计、应力外场诱导等手段，获得了系列拉伸强度高、断裂伸长率大的PHBV复合纤维。首先，研究了异相成核对PHBV/WS2复合材料等温结晶行为和结晶形貌结构的影响关系，探讨了牵伸诱导对纤维晶体结构与力学性能的内在规律，建立了异相成核与牵伸诱导纤维晶型转变机理，解决了初生纤维粘连问题。其次，通过反应共混制备了长链支化PHBV(LCB-PHBV)，研究了长链支化、牵伸诱导、扭转拉伸对LCB-PHBV高熔体强度和快结晶速率的调控关系，建立了反应加工、速冷成核与多级牵伸协同新技术, 实现了LCB-PHBV高成核温度、快结晶速率和高热稳定性的性能集成, 克服了PHBV熔体强度低、喷头拉伸控制难的问题。再次，通过分子链缠结、异相成核和应力外场控制等研究了复合纤维的微结构调控与宏观力学性能之间的影响关系，建立了异相成核与长链支化协同诱导PHBV晶型转变新方法，进一步获得了高β晶含量、高取向和高力学性能的PHBV熔纺纤维。项目研究成果在Composites Science and Technology等期刊发表SCI论文11篇，授权发明专利5项，培养博士后、研究生等5人。本项目为生物基聚酯的应用开发提供了一定的理论基础和技术支撑。