功能化石墨烯对聚合物/石墨烯纳米复合材料发泡行为的影响研究

The proposal is focused on the preparation of polymer/graphene nanocomposites and studies on the foaming behavior of polymer/graphene nanocomposites, based on previous results on the preparation of graphene, functionlized modification of graphene, preparation of polymer/graphene nanocomposites and foaming of polymer and polymer nanocomposites using supercritical CO2 as physical blow agent in my research group. polymer (PP and PS)/graphene nanocomposites will be prepared via direct melt compounding (mixer or twin screw extruder) using modified graphene, in which the graphene has cotrollable C/O ratio, higher surface area and good electrical conductively, prepared using low temperature exfoliation method of graphene oxide(GO). The targeted homogeneous dispersion of graphene in polymer matrix is achieved using the compatibilizer, which will be in situ formed via π-π stacking interaction for PS/graphene nanocomposite and PP(PS)/modified graphene nanocomposites or using commercial PP-MAH and SMA polymer as compatibilizer. The foaming behavior of polymer/graphene nanocomposites is investigated using in situ image technology to reveal the effect of modified graphene on the cell nucleation, cell growth and stabilization of polymer during the foaming process. The polymer nanocomposite foams are prepared by batch foaming(PS matrix), reactor foaming(PP matrix) and continuous extrusion foaming (PP and PS matrixes) using supercritical CO2 as physical blow agent. The mechanical, electrical and EMI properties of polymer/graphene nanocomposite foams are characterized and studied to correlate with the foam structure and morphology.

本研究在已进行的关于石墨烯制备、改性及聚合物/石墨烯纳米复合材料及聚合物微孔发泡研究基础上，利用制备出具有不同结构特性（包括不同C/O比、比表面积和电导率等）的石墨烯，通过对石墨烯进行功能化改性，利用熔融共混制备出不同石墨烯/聚合物体系的纳米复合材料，研究具有不同分子链结构的聚合物与石墨烯在熔融共混下的相互作用及作用机制，实现石墨烯在聚合物中的均匀分散。选择两大类聚合物的代表即非晶的聚苯乙烯（PS）及结晶的聚丙烯（PP）为聚合物基体材料，利用CO2为发泡剂，结合微孔发泡原位成像技术研究石墨烯对聚合物微孔发泡过程中泡孔成核及生长的影响；使用间歇发泡（包括釜压发泡等）及连续挤出发泡等实验方法对聚合物/石墨烯纳米复合材料的发泡行为进行系统研究，研究发泡过程中功能化石墨烯对于聚合物泡孔成核、生长及抑制泡孔聚并与稳定化的影响及微孔结构的形成对于聚合物/石墨烯发泡材料力学、导电和电磁屏蔽性能的影响。

本项目以低温热膨胀还原的石墨烯或高温热还原的石墨烯为功能填料，通过熔融共混或溶液共混的方式与聚乳酸、聚丙烯、热塑性聚氨酯等聚合物进行复合，并根据各自特点选择超临界二氧化碳发泡或相分离发泡技术手段制备高性能功能性发泡材料，期间研究了石墨烯对聚合物微孔发泡过程和行为的影响，同时也结合聚合物/石墨烯发泡材料以及石墨烯基碳泡沫考察了微孔结构的形成以及宏观结构设计对于微孔发泡材料导电和电磁屏蔽性能的影响。结果表明：石墨烯作为异相成核剂能显著增强泡孔成核过程，稳定泡孔尺寸；同时发泡过程使得泡孔壁受到强烈的双向拉伸作用有利于石墨烯在基体中进一步分散，从而使得发泡材料具有更低的导电逾渗阈值。另外，微孔结构在电磁屏蔽过程中可以大大增强电磁波在泡孔内部的多重反射衰减，从而进一步提升材料对电磁波的吸收性能。除此之外，通过梯度结构和三明治结构设计可以分别增强聚合物/石墨烯复合多层泡沫在电磁屏蔽过程中对电磁波的吸收性能或总屏蔽效能。