聚酰亚胺薄膜层叠体热处理过程中的结构演变

The Structure Evolution of PI Sheaf During Heat Treatment

将双向拉伸PI薄膜,层叠后经800℃炭化所得样品在热压机中进行从2 500℃到2 800℃的高温石墨化处理制得了高定向石墨材料。借助SEM、XRD、四探针法等测试手段分析了PI薄膜层叠成型体在热处理过程中尺寸、传导性能、微观结构等的变化。结果表明石墨化处理后,样品径向增大,厚度减小;2 800℃处理后材料层间距接近单晶石墨的理论层间距,表现出了较高的石墨化程度,且具有高的取向性和传导性能,根据电阻率与热导率的相关公式推得其热导率为1 000 W/(m.K)～1600 W/(m.K).在整个热处理过程中,所生成的物质继承了原料分子的取向性。

The highly-oriented graphite was prepared from bi-oriented polyimide（PI） films by the processes involving in piling up several PI films to form a multi-layer film,which was carbonized into the multi-layer film at 800 ℃ and was pressed under high temperature graphitization treatment by a hot-pressing machine at 2 500 ℃ and 2 800℃.The variation of dimensions,conductivity and microstructure of the PI sheaf were analyzed by using SEM,XRD and the four-probe method.The results showed that the sheaf was increased along the radial direction and its thickness was decreased.After the thermal treatment at 2 800 ℃,the PI sheaf with crystalline parameter d002 close with the theoretical interlayer distance of single crystal graphite had high oriented and conductive properties and displayed the high graphitization degree.The thermal conductivity of PI sheaf deduced from Mason formula was 1 000 W/（m.K）～1 600 W/（m.K）.The PI sheaf maintained the orientation property of the raw material during the whole heat treatment process.