动态硫化可控制备高强韧PLA/CPU/MXene纳米复合材料及其强韧化机理

Elastomer has been proved to be a prominent toughener for poly (lactic acid) (PLA), however, the remarkable increase in toughness always accompanies a sharp decrease in tensile strength and modulus. High-performance PLA materials with balanced stiffness-toughness can be achieved by synergistically using elastomer and rigid inorganic nanofiller and controling the selective distribution and uniform dispersion of nanofiller in the elastomer toughening phase. In this project, two-dimensional MXene nanosheets is first intercalated and pre-dispersed with water soluble polyethylene glycol (PEG), and then subjected them to dynamic vulcanization with PLA/multifunctional isocyanate crosslinker (MIC) to "one-step" and green fabricate PLA/crosslinked polyurethane (CPU)/MXene nanocomposites with balanced stiffness-toughness. The effect of processing parameters (temperature, time, etc.) and composition (PEG molecular weight and loading, MIC type and loading, etc.) on the dynamic vulcanization kinetics and thermodynamics will be thoroughly investigated, and the dynamic vulcanization mechanism will be understood. Based on the above research, the effect of MXene on dynamic vulcanization kinetics and thermodynamics, and the microstructure and properties of composites will be studied. By regulating the dispersion, distribution and interface interaction of MXene in PLA/CPU blends, the high performance PLA/CPU/MXene nanocomposites with balanced stiffness-toughness will be controllable prepared via dynamic vulcanization. Disclosing the relationship between the morphology, structure, and performance of PLA/CPU/MXene nanocomposites, the strengthening-toughening mechanism will be explained. Overall, this project not only provide new ideas for the industrial preparation of high-performance PLA with balanced stiffness-toughness, but also provide theoretical support for expanding the application of MXene in the field of polymer composites, which has important academic and practical application value.

脆性聚乳酸与弹性体共混虽可提高韧性，却损失了强度和模量。调控刚性无机纳米材料定向分布且均匀分散于弹性体相，经两者协同作用可实现聚乳酸的高强韧化。本项目拟在水介质中以聚乙二醇插层预分散MXene纳米片，通过聚乳酸/聚乙二醇-MXene/异氰酸酯交联剂多元体系的动态硫化，一步绿色制备高强韧聚乳酸材料。研究工艺条件和组分配比对聚乳酸/聚乙二醇/异氰酸酯交联剂体系动态硫化反应动力学与热力学过程的影响机制，阐明动态硫化反应机理。在此基础上研究MXene对动态硫化反应过程及共混物微结构和性能的影响规律，调控MXene的分散分布及其与树脂基体的界面相互作用，探究共混物形态-结构-性能的构效关系，阐明强韧化机理，实现高强韧聚乳酸的动态硫化可控制备。项目成果不仅可为制备高强韧聚乳酸提供新思路，还可为扩展MXene在聚合物复合材料领域的应用提供理论支持，具有重要的学术和实际应用价值。

针对弹性体增韧脆性聚乳酸虽可提高韧性但却易降低其强度和模量的问题，提出通过调控刚性无机纳米材料定向分布且均匀分散于弹性体相，经两者协同作用来实现聚乳酸高强韧化的策略。通过控制乳化剂用量、核壳层单体比例及功能单体种类和含量，合成了不同粒径分布和不同核壳比的聚丙烯酸酯核壳乳液，讨论了不同核壳结构的聚丙烯酸酯含量对聚乳酸增韧效果的影响，研究发现，引入少量活性GMA单体，有助于提高聚乳酸和聚丙烯酸酯的界面相互作用，从而改善增韧效果；同时，讨论了不同的聚乙二醇分子量和用量、交联剂种类和用量及动态硫化温度、时间等工艺条件对聚乳酸/聚乙二醇/异氰酸酯交联剂体系动态硫化过程中各组分交联反应速度和交联密度的影响，研究发现，采用较小分子量聚乙二醇有助于提高交联聚氨酯的交联密度，从而对聚乳酸起到更好的增韧效果。在此基础上，分别在水介质中以聚丙烯酸酯胶乳和聚乙二醇插层预分散MXene纳米片，通过冷冻干燥得到MXene纳米片被充分剥离并均匀分散的聚丙烯酸酯/MXene共混物和聚乙二醇/MXene共混物，且所引入的聚丙烯酸酯和聚乙二醇分子链显著增大了MXene纳米片的层间距，从而改善熔融加工过程MXene纳米片的剥离和分散。进一步，在此基础上，结合原位反应界面增容的熔融共混和动态硫化技术，分别实现了MXene纳米片在树脂基体中的均匀分散以及在聚丙烯酸酯和交联聚氨酯中的定向分布，从而制备得到高强韧的聚乳酸/聚丙烯酸酯/MXene三元纳米复合材料和聚乳酸/交联聚氨酯/MXene三元纳米复合材料，研究结果表明，仅0.125-0.25wt%均匀分散且定向分布的MXene纳米片即可显著提高复合材料的拉伸强度。项目研究成果不仅为制备高强韧聚乳酸提供新思路，还为扩展MXene在聚合物复合材料领域的应用提供理论支持，具有重要的学术和实际应用价值。