Analysis Of Morphology Of PP Micro Arrays Manufactured By Micro Injection Molding

For material molding, morphology determines mechanical performance. Yet the current research of morphological analysis is far from adequate, therefore study of morphology establishes great significance to improvement of mechanical and even service performance of microstructured components.Design and manufacture micro injection mould which includes two parts: main body and micro insert. The insert is 10×10 micro blind hole arrays in 400μm silicon die made by photo etching and ion etching. There are three specifications for it, whose diameters are respectively 60μm, 110μm and 130μm; and heights are both 250μm. On such basis, three kinds of Polypropylene (PP) microstructured column arrays are obtained, whose diameters are accordingly 60μm, 110μm and 130μm, and heights are both 250μm.The effects of molding parameters, such as mold temperature, injection pressure and mold vacuum on the microstructures are also investigated. Experiment results reveal that the micro columns under inappropriate parameters have some defects, such as short filling, rough surface, hollow and ablation; and that they are entirely filled without the above defects under appropriate ones: mold temperature at 90℃, injection pressure at 100 MPa, hold time by 3 s and mold vacuum.Analyze morphology of micro columns without defects by polarized light microscope (PLM), scanning electronic microscope (SEM) and micro-area X-ray diffraction instrument (MXRD). A three-layer hierarchy similar to routine injection components, known as " skin-core structure", is observed by PLM, with amorphous surface, column crystal shear zone and spherocrystal core zone outside-in. Yet there is some dissimilarity as well: thinner amorphous surface and larger shear zone. The different sizes of spherocrystal are presented by SEM, with the larger ones closer to core. Columns with different diameters have various spherocrystal sizes and distributions. The dimension of spherocrystals with diameter of 110μm is comparatively smaller than that of ones of 130μm. Crystalline mode of the components was revealed by MXRD with such results as bothαandβin micro column and base shear zone, and onlyβin base core. There exist moreβin column with diameter of 110μm than the one of 130μm.