The Effects Of TMB-5 On The Crystallization Structure Of IPP

Study of crystallization in polymers has drawn much interest in recent years, because it implies the possibility of predicting and controlling the final structure and properties of semi-crystalline polymers. Polypropylene(PP) is a semi-crystalline polymers well known as its abundant raw material source, low price and excellent comprehensive performance,so that it is widely used in various industries, such as auto industry and consumer goods, etc.PP is usually the alpha crystal type, which is light, heat resistance, corrosion resistance, but its high hardness, poor toughness limits its range of applications. But polypropylene containing beta crystals has good ductility and toughness. The study of isotactic polypropylene with β-nucleating agent has aroused a great interest of scientists.In this work, polarizing optical microscope, wide-angle X-ray diffraction, small-angle X-ray diffraction and differential scanning calorimetry were used to explore the influence of nucleating agent content of beta crystal, the crystallization temperature and the cooling rate on the crystallization behavior of polypropylene.It was found that after the addition of nucleating agent, spherulites quickly filled with vision at the same time, but the spherulite of pure iPP growed slowly. With the increased nucleating agent content, the spherulite numbers increased and the size decreased dramatically. The content of beta crystal reaches the critical value as the nucleating agent content is 0.1wt%; above it, the content of beta crystal almost keeps a stable value. For i PP with β-nucleating agent, when the crystallization temperature is higher than 140 centigrade, it can inhibit the growth of beta crystals.The effect of temperature on the crystallization behavior was investigated by means of the melt isothermal crystallization, and it was found that the content of beta crystals could be increased obviously after the addition of nucleating agent. We found that for the specific content of β-nucleating agent, the degree of crystallinity keeps at a stable value and is independent of the crystallization temperature. With the increase of crystallization temperature, the lamellar thickness gradually increased, and the degree of perfection of the crystal also increased, which leads to the shift of the melting peak to the high temperature.For the pure iPP and iPP with β-nucleating agent cooling at different rates, it was found that with the increase of cooling rate, the crystallization peak became more and more wider, the crystallization temperature gradually shifted to low temperature zone. We also inferred that before the crystallization of polymer, there has been a pre-ordered structure – mesophase.