Abstract: A surface modification of calcium sulfate whiskers was performed by using a KH-550 silane coupling agent, and their structures before and after the surface modification were investigated comparatively by Fourier-transform infrared spectroscopy. The crystallization and melting behaviors of polypropylene (PP) nucleated with β-nucleating agent (TMB-5), surface-modified CaSO4 whiskers(K-CSW), and a mixture of CaSO4 whiskers and TMB-5 were studied by differential scanning calorimetry, and the nucleating effects of these three nucleating agents were compared. The results indicated that the K-CSW could effectively promote the formation of β-crystals and it also exhibited a synergistic nucleating effect with TMB-5, thus resulting in an improvement in crystallinity of PP. When 0.2 wt % of TMB-5 and 2 wt % of K-CSW were incorporated into PP, the relative content of β-crystals in PP reached 90.1 %, and the peak crystallization temperature of nucleated PP increased to 127.2 ℃ from 122.3 ℃ of pure PP.

Key words: β-nucleating agent, calcium sulfate whisker, polypropylene, synergistic nucleating effect