Effects of cooling conditions on the crystal structures of the matrix in knitted glass fabric reinforced polypropylene composites

Four groups of knitted glass fabric reinforced polypropylene (PP) composites with different cooling conditions are prepared by changing the method used in the cooling period. The crystal structure of the matrix in composites arising from different cooling conditions is studied using wide angle X-ray diffraction. It has been found that the various cooling conditions have no effect on the crystal types of the PP matrix. However, the crystal degree and sizes of microcrystal and spherulite vary with cooling conditions. They increase with the decrease of the cooling speed and the prolongation of the cooling time.