水辅混炼挤出聚合物/石墨烯纳米复合材料的结构与性能

Polymer/graphene nanocomposites exhibit extensive applications due to their superior properties. However, there is still a great challenge in their large-scale preparation. In this project, pioneering researches are carried out on preparing this kind of nanocomposites via water-assisted mixing and extrusion. Key set-up for water-assisted mixing and extrusion is developed. Fundamental scientific issues during water-assisted mixing and extrusion of polymer/graphene nanocomposites are investigated. The deformation and breakup of aqueous suspension droplets of graphene within flowing polymer melt in the extruder are investigated by combining visual experiments with theoretical analyses. The polymer/graphene nanocomposites are prepared via two incorporated modes of the graphene under different processing conditions. The rheologies, microstructure/phase morphology, and properties of the as-extruded nanocomposites are investigated and analyzed. Then the relationship among processing flow fields, rheologies, microstructure/morphology, and properties is analyzed. Based on the aforementioned results, the mechanism is revealed for synergistic promotion of the exfoliation and dispersion for the graphene and of the formation and development for the microstructure/morphology in the as-extruded polymer/graphene nanocomposites by both water and complicated processing flowing fields. This research work can help to promote the exfoliation and orientation of the graphene in polymers, and provide a theoretical base for preparing polymer/graphene nanocomposites with high properties and functionalities in a large-scale, continuous, and efficient way. Moreover, this work is expected to prompt the inventive principles and techniques for preparing novel materials.

聚合物/石墨烯纳米复合材料因其优异性能而具有广阔的应用前景，但目前其规模化制备方面仍存在很大挑战。本项目率先提出采用水这种绿色介质辅助混炼挤出技术制备这种纳米复合材料，自主研制水辅混炼挤出的关键装置，研究制备过程中的基本科学问题。采用可视化实验和理论分析相结合的方法，研究挤出机流场作用下石墨烯/水悬浮液滴在熔体中发生的形变和破裂过程。采用单种聚合物和共混物，通过两种石墨烯加入方式，并改变加工条件，制备纳米复合材料，研究、分析其流变行为、结构形态和性能，分析流场-流变-结构形态-性能之间的内在有机联系。在此基础上，揭示水和复杂加工流场协同促进石墨烯片层剥离和分散以及聚合物/石墨烯纳米复合材料结构形态形成和演变的机理。通过本项目研究，可促进石墨烯在聚合物中良好地分散和排列，为批量、连续、高效地制备高性能、功能化的聚合物/石墨烯纳米复合材料提供理论依据，有望获得制备新材料的创新原理和关键技术。

聚合物基纳米复合材料（尤其含石墨烯）因其优异性能而具有广阔的应用前景，但目前其规模化制备仍存在很大挑战。.主要研究内容：.1. 研制了水辅助混炼挤出的关键装置，构建一套与水辅助混炼挤出设备相连的可视化观测系统。.2. 采用在线可视化、实时观察实验并结合理论分析，对挤出机螺杆流场作用下水悬浮液滴在熔体中发生的流动、形变和破裂过程进行了研究。.3. 采用研制的水辅助混炼挤出设备，通过改变注水相关参数和螺杆结构等，连续制备了以下几种聚合物基（纳米）复合材料：.1）聚偏氟乙烯/氧化石墨烯（PVDF/GO）纳米复合材料和聚苯乙烯（PS）/PVDF-GO共混物纳米复合材料.2）聚甲基丙烯酸甲酯/膨胀石墨（EG）和聚丙烯/EG复合材料.3）PVDF/埃洛石纳米管（HNTs）和PP/HNTs纳米复合材料.对制备的纳米复合材料的线性和非线性黏弹行为、微观结构/相形态和晶体结构以及宏观性能和功能性进行了较全面的研究，分析了流变–结构形态–性能之间的内在有机联系。.4. 综合上述研究结果并结合挤出机螺杆的混炼流场，分析、揭示了水辅助混炼挤出（WAME）过程中注入的水和混炼流场协同促进纳米粒子剥离和分散以及聚合物基纳米复合材料结构形态和晶体结构演变的机理。.重要结果、关键数据及其科学意义：.1. WAME过程中注入的水促进了GO的插层、剥离和分散，揭示了水促进GO片表面含氧基团与PVDF分子链之间相互作用的机理，尤其是揭示了水促进GO分别与PS和PVDF相之间的相互作用以及促进GO增容PS与PVDF的机理。.2. 注入的水促进了EG的插层、剥离和分散，揭示了水促进EG与PMMA或PP之间相互作用从而提高复合材料热导率的机理。仅7 wt% EG使PMMA热导率提高3.1倍。.3. 揭示了水同时促进GO在PVDF中剥离和分散以及原位热还原从而提高PVDF/GO纳米复合材料热传导性能的机理。仅1 wt%的GO使PVDF热导率提高1.3倍。.4. 揭示了水促进HNTs在PVDF中分散并提高PVDF/HNTs纳米复合材料的β晶含量、塑性形变和熔体可拉伸性的机理。.据本项目组成员所知，上述结果是通过本项目研究首次获得的。