Junhong Li

X-ray analysis on crystal structures of crystalline polyimides

A high performance engineering plastic material based on crystalline polyimide was prepared by hot-press method after the resin was synthesized. The mechanical properties including tensile properties, compression properties, bending properties, impact toughness, shearing strength were first investigated. The material displayed excellent mechanical properties and could be used at high temperatures. Since the tensile experiment was operated at 25°C, 250°C and 280°C, respectively. So the progress of crystals grown was affected by load and temperature at the same time, and residual stress would be existed in the samples. X-ray diffraction experiments were then conducted to investigate the difference of crystal structures formed under different conditions. Results indicated that the main diffraction peaks were almost same, but the position of some week peaks changed a little. The material then isothermally crystallized at different temperatures and they displayed same crystal structures by X-ray diffraction experiment.