直接混炼法制备膨胀石墨导电母料的研究

【作者】 李玉超；

【导师】 陈国华；

【作者基本信息】 华侨大学 ， 材料学， 2007， 硕士

【摘要】 蠕虫状膨胀石墨EG表观密度很低,膨胀体积很大,且纳米石墨片相互纠缠在一起,造成了很多气孔的存在。这致使膨胀石墨极易团聚,与聚合物复合加工困难,不易实现理想的纳米复合。若将其应用于工业生产中,也必会造成大量的能源和能量上的浪费。解决这一缺陷,必须对膨胀石墨预先进行改性处理。母料法制备聚合物/膨胀石墨复合材料是一种新型的制备膨胀石墨填充聚合物导电复合材料的方法。本硕士论文就是基于该母料法的特点,利用原位聚合和熔融复合各自独特的优点预先对膨胀石墨进行改性处理,制成了分散性较好的聚合物/膨胀石墨的浓缩体(即母料);然后以该母料为填料,实现了母料法制备聚合物/膨胀石墨导电复合材料。本文研究了不同制备方法、不同载体树脂对膨胀石墨的改性效果;表征了膨胀石墨在各种母料中的分散状态;比较了母料法制备复合材料较直接复合方法制备复合材料在电学和力学性能上的优劣;同时借助XRD、SEM、DSC等基本手段对复合材料的晶体结构、表面形貌、结晶和熔融等行为作了研究,系统阐述了复合材料结构与性能之间的关系。研究的主要结果表明:利用MMA单体原位聚合法改性的膨胀石墨母料,MMA单体部分渗入到EG片层内,所得母料具有优异的电学性能;但当EG含量高于20 wt%后,聚合变得很困难,不利于改性石墨母料的批量制备。利用PMMA树脂通过熔融复合制备的改性膨胀石墨母料,PMMA大分子链不能插入到EG片层之间,但在刚性PMMA分子链的阻碍作用下,EG蠕虫状的结构被破坏,使EG片相互剥落,以纳米石墨薄片的形态存在于基体中。基于这一点,母料法成功地实现膨胀石墨的纳米分散,减少了超声制备纳米石墨薄片的复杂步骤,较易地制备纳米复合材料。本文还研究了以结晶性PE和非结晶性PS为载体改性膨胀石墨母料以及母料法制备HDPE/EG复合材料的电学、力学和热学等性能。结果表明,以聚合物树脂为载体制备的改性膨胀石墨母料,浓缩物中EG含量以60 wt%为宜。该含量下,膨胀石墨可以较好的分散于载体树脂中,母料法制备的HDPE/EG复合材料具有较低的渗流域值,膨胀石墨在基体树脂中的分散性得到了很大的提高,同时改善了复合材料的机械性能和热学性能。更多还原

【Abstract】 Vermicular expanded graphite (EG) has a big bulk volume because of small apparent density. The graphite sheets are tangle with each other with big open and close pores in it which leads to easy agglomeration and difficulty in mixing with polymers. It may consume much energy in industrial manufacture to achieve well-dispersed materials. Thus, EG should be modified before use in order to solve this problem.Master-batch process is a new way in the preparation of polymer/EG conducting composites. According to the advantages of in-situ polymerization and direct melt blending, EG was first pretreated to be well-dispersed concentrates (i.e. master-batch). Then, blending this modified graphite (MG) as a kind of filler with other polymers. Polymer/EG conducting composites were prepared by master-batch filling process. The effect of different preparation methods and different carriers on EG dispersion state were studied in this article. The electrical and mechanical properties prepared by master-batch process and direct-melt blending process were compared in assistance with XRD, SEM, DSC. The relationship between structures and properties was elucidated systematically.Results showed that EG master-batch modified by in-situ polymerization of MMA monomer had excellent electrical properties. However, it was hard for MMA to cure when EG content higher than 20 wt% which limited its uses. Another investigation showed that EG tangled structure was almost destroyed into isolated pieces when direct melt-blended EG with PMMA resin. From this point of view, master-batch process had successfully achieved nanoscale dispersion of EG. In addition, polymer/graphite nanocomposite could be easily done by master-batch filling technique without the complicated process that graphite nanosheets were first made by sonication.Crystalline PE and noncrystalline PS were studied as carriers in the preparation of EG master-batches. Electrical, mechanical and thermal properties of HDPE/EG composites made by master-batch filling process showed a perfect master-batch content of 60 wt% where the percolation threshold was very low and its mechanical and thermal properties were also enhanced.更多还原