Crystal distribution and molecule orientation of micro injection molded polypropylene microstructured parts

Polypropylene (PP) microstructured part which comprises micro columns array and a macroscopical base plate was manufactured by micro injection molding. The morphology distribution in micro columns is quite different from that of the base plate. This article investigates the crystal distribution and molecule orientation of the microstructured part by X-ray diffraction. The hardness of shear zone of micro columns was evaluated by Nano Indenter. Test results show that both micro columns and macroscopical base plate contain α and β phase. However, the relative proportion of β phase in micro columns is markedly higher than that of the base plate. β phase distributes only in the shear zone of the microstructured part. So, the mechanical properties of micro columns must differ from that of the base plate. In addition, the orientation of 100 μm micro columns is slight, which indicates that the mechanical anisotropy of micro columns induced by orientation could be ignored. POLYM. ENG. SCI., 49:1661-1665, 2009.