Abstract: Molecular weight and distribution, crystallization behavior, and mechanical properties of polypropylene (PP) powers with different particle sizes were studied using differential scanning calorimetry and gel permeation chromatography. It was found that the molecular weight and distribution, crystallization temperature, crystallization rate, nucleating ability, and mechanical properties of PP were all obviously influenced by initial particle sizes of PP power. PP powers with small particle sizes had higher number-average molecular weight, wider molecular weight distribution, and higher melt flow rate. With decreasing particle sizes of PP powers, crystallization temperature, initial crystallization temperature, initial crystallization rate, and nucleating ability increased, tensile and impact strengths decreased, and spherulits became more uniform and finer.

Key words: polypropylene, particle size, relative molecular weight, relative molecular weight distribution, crystallization behavior, mechanical property