松香型聚丙烯成核透明剂成核机理的研究

Dehydroabietic acid was separated and purified from disproportionated rosin, the effects of rosin-type nucleating agent, which was prepared from co-crystallizing of dehydroabietic acid, potassium dehydroabietate and sodium ehydroabietate, on polypropylene crystallization were studied. The results of Differential Scanning Calorimeter(DSC) and X-ray Diffraction proved that the cocrystal of dehydroabietic acid, potassium dehydroabietate and sodium dehydroabietate[Nu-(K+Na)] was formed, rather than a simple blend of single metallic salts. When it was added in PP, the size of PP spherulite was decreased; the mechanical properties, crystallization temperature and transparency of PP could be substantially improved. Thus Nu-(K+Na)could act as a more effective nucleating agent for PP. The influence of rosin-type nucleating agent Nu-(K+Na) and low density polyethylene (LDPE) on the crystallization process of polypropylene (PP) from the melt state was studied by DSC and polarization microscope (PLM) also. It was found that the cooperative effect of 3%LDPE and Nu-(K+Na) made the crystallization rate of PP increase greatly, the spherulites of PP became much smaller and dispersed more uniformly, and the transparency of PP was further improved evidently, thus LDPE could decrease the amount of Nu-(K+Na) added. Kinetic analysis of PP isothermal crystallization showed that LDPE and Nu-(K+Na) decreased the fold surface energy of the developing crystals of PP, promoted the nucleation and crystallization of PP.

以歧化松香为起始物，完成了脱氢枞酸分离与纯化，研制成功脱氢枞酸及脱氢枞酸钾，钠复合盐共晶成核剂。该成核剂不是钠盐与钾盐共晶型成核剂的简单混合物，它有着与之不同的熔点与X射线衍射峰。它在聚丙烯中较单盐成核剂成核效果更好，极大改善聚丙烯的透明性，提高聚丙烯的弯曲模量，冲击强度及结晶温度。研究了在少量聚乙烯协同作用下，上述成核剂对聚丙烯结晶过程，结晶动力学及结晶形态的影响。结果表明：3%的LDPE加入聚丙烯中，有效地协助成核剂在聚丙烯中分散，强化了成核剂的成核能力，使聚丙烯半结晶时间大大缩短，并降低了聚丙烯结晶的界面自由能，使聚丙烯球晶变小，透明性增强，聚乙烯的加入可降低上述成核剂的用量并取得较好的成核效果。