低缺陷石墨烯/UHMWPE纳米复合材料的制备、结构与导电性能研究

High-quality Graphene/UHMWPE Nanocomposite:Preparation,Structure and Electrical Performance

设法以简单的工艺实现低缺陷石墨烯的高效、规模化制备,对于促进其在聚合物改性领域中的成功应用具有重要意义。本文报道了一种低缺陷石墨烯的简单制备方法及其对超高分子量聚乙烯(UHMWPE)的复合改性作用。首先,利用超支化聚乙烯(HBPE)在氯仿中借助超声高效剥开天然石墨制得石墨烯分散液,然后分别与两种不同粒径的UHMWPE粉末进行溶液混合,经溶剂挥发和热压成型制得石墨烯/UHMWPE复合材料。利用透射电子显微镜(TEM)、原子力显微镜(AFM)、X射线光电子能谱(XPS)、拉曼光谱(Raman)、广角X射线衍射技术(WAXRD)和扫描电子显微镜(SEM)等手段对所得石墨烯及其复合材料的结构进行了深入表征,并对所得复合材料的导电性能进行了评价和比较。结果表明:所得石墨烯结构缺陷较少,厚度5层以下,表面存在少量非共价吸附的HBPE,比例达0.39 g(g石墨烯)-1;通过所述复合工艺可制得具有隔离网络结构的石墨烯/UHMWPE复合材料,借助该结构,只需少量石墨烯即可有效提高UHMWPE的导电性能,其逾渗阈值仅为0.25 vol%(粒径60μm UHMWPE)和0.50 vol%(粒径25μm UHMWPE);相比小粒径UHMWPE粉末,由大粒径粉末所得复合材料具有更低的石墨烯导电愈渗阈值及更优的导电性能。相关研究结果可为低缺陷石墨烯的高效制备及应用提供重要的实验基础。

It is of significant importance to obtain high-quality graphene in large scale through relatively simple process for successful applications of graphene in polymer modification fields. We herein report a facile method for the high-efficiency production of high-quality graphene and its modification effects on ultra- high molecular weight polyethylene (UHMWPE). Stable dispersions of graphene were first prepared by noncovalently exfoliating graphite in chloroform with a hyperbranched polyethylene (HBPE) under assistance of ultrasonication, and then were mixed with two kinds of UHMWPE powders having different particle sizes, followed with drying and hot- pressing to give a series of graphene/UHMWPE composites. The structures of the as- prepared graphene and its composites were systematically characterized with different technologies, including transmittance electron microscopy (TEM), atomic force microscope (AFM), X- ray photoelectron spectroscopy (XPS), wide- angle X- ray diffraction(WAXRD), Raman spectroscopy and scanning electron microscopy (SEM), respectively. Meanwhile, the electrical performance of the resulting composites was also evaluated and compared. The as-obtained graphene is confirmed to be low structurally defective and have a thickness lower than 5 layers, with some HBPE (0.39 g (g graphene)- 1) irreversibly adsorbed onto its surface by means of noncovalentint eractions. The graphene/UHMWPE composites are found to have a segregated graphene network structure and thus exhibit greatly improved electrical conductivity upon addition of little graphene with percolation thresholds low as 0.25 and 0.50 vol% for UHMWPE having particle size of 60 and 25 μm,respectively. The particle size of UHMWPE powder has a significant influence on the electrical conductivity of the resulting composite at a given graphene loading, that is, the bigger the particle size,the lower the graphene percolation threshold. The results found herein may provide important experimental basis for the scalable production and application of high-quality graphene.