表面修饰纤维素晶须改性生物质基聚酯材料结构与性能研究

In order to improve the miscibility between cellulose whisker (CW) and hydrophobic polymeric matrix, inhitbt the self-aggregation as high loading-level of CW and enhance thermal stability of CW for melting compounding and thermoforming, the surface structure and properties of the modified CW will firstly be regulated by controllable chemical reaction in this project, and then be used to modify the biomass-based polyesters, such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS) and so on, by melting compounding and thermoforming techniques. Based on the research on surface modification of CW and melting compounding techniques of CW-based nanocomposites, in situ chemical modification of CW surface in the process of melting compounding will be explored. Furthermore, it is expected to develop high-performance cellulose whisker (CW)-modified materials and establish relevant structural design theory and large-scale preparation technique. Hence, to understand the regulation mechanism of the structure and properties on the CW surface toward the micro-strcuture and performances of the as-prepared nanocomposites, the characterization methodology and especially the study on the interface between filler and matrix will be developed, and, meanwhile, the reaserch ideas of the structrue-properties relatioship, including the effects of physical and chemical properties of the CW surface on the interfacial structure and interaction with matrix, the changes of the matrix organization and so on, will be established. This project will enrich the research on the cotrollablity of surface chemical modification of CW, extend the application of CW as a reinforcing filler and provide the large-scale preparation techniques of CW-based nanocomposites. Furthermore, these methods and techniques as the guideline will be used to develop the foaming materials based on CW-modified polyester, and hence be expected to produce new CW-based materials with great application potential.

为了解决纤维素晶须（CW）与疏水性基质的相容性、高含量复合改性时易团聚、热稳定性无法达到熔融复合和热成型加工要求等共性问题，以期发展高性能纤维素晶须改性材料及相适应的材料结构设计理论和规模制备技术，本项目通过可控化学修饰方法改造CW的表面结构和性质，将表面修饰的CW与聚乳酸、聚丁二酸丁二醇酯等生物质基聚酯熔融复合、热加工成型；基于表面修饰方法和熔融复合技术的研究，探索CW在熔融复合过程中原位修饰的技术方案。进而，针对CW表面结构和性质调控纳米复合体系结构和性能的机制，发展以填料/基质界面为重点的结构表征方法体系，建立涉及填料表面物理化学特性及其影响的与基质的界面结构和相互作用、基质微相结构变化等较全方位的评价方案。本项目将丰富CW表面化学修饰可控性方面的研究内容，为拓展CW作为增强填料广泛应用及其复合改性材料规模化生产提供科学依据，指导CW改性聚酯发泡材料的研制，提供具有应用潜力的新材料。

纤维素晶须（CW）作为一种高强高模的生物质纳米填料，被尝试用于生物质基聚酯材料的增强增韧及功能化，但受限于其亲水表面与疏水聚酯的相容性欠佳。申请人前期研究发现CW表面化学修饰可改善CW对生物质基聚酯的改性效果。因此，在前期工作基础上，本项目围绕CW表面化学调控及可控性，发展了酯基、巯基、炔基、多巴基等官能基的酸酐酯化、硅氧烷化等修饰方法以及内酯开环聚合接枝的离子液体反应体系，特别是利用酸酐酯化制备出相比于TEMPO氧化法对表面结构破坏程度低的高羧基含量的CW，同时乙酸酐酯化可控制取代度差异呈约10%的梯度，表面修饰2-16个碳原子甚至更高的碳链可控制于25-30%取代度范围内。通过调控乙酸酐酯化取代度，发现提高取代度可促使CW表面能与聚酯更为相近，有利于CW在基体中的分散，具有更好的增强效果并且减少了延展性的下降。进而，结合逾渗网络理论，疏水改性时在CW表面引入羧基，可在聚酯基体中形成与其相容性好的CW网络，促使模量、强度和伸长率同步分别提升4.5%、140%和200%。拓展CW改性聚酯的应用，利用CW提高聚酯熔体强度的特点，发展了CW改性聚丁二酸丁二醇酯的发泡材料，提高了弯曲强度和弯曲模量。通过CW表面化学修饰引入能与基体化学耦合形成共连续结构的官能基，针对热固性聚合物材料体系构建填料与基质多位点接枝的星系型网络结构，证明了该高性能化改性理念适用于一维棒状纳米粒子并将填料与基质反应类型拓展到Click型Huisgen反应。仅添加1.0 wt%的炔基化CW就促使强度、模量和伸长率同步提高了103%、100%和12%。综上所述，本项目研究结果证明了CW表面修饰对CW/聚酯界面及聚酯材料多级结构与性能的调控能力，发展了CW高值利用途径并促进了生物质基聚酯材料的应用，丰富了纳米填料表面结构微小变化对材料结构与性能的放大效应与调控机制等理论研究内容。