山梨糖醇/稀土复合成核剂对等规聚丙烯非等温结晶行为的影响

Effect of the Composition of α/β Compound Nucleating Agents on Nonisothermal Crystallization Behavior of Isotactic Polypropylene

采用差示扫描量热仪(DSC)研究了山梨糖醇/稀土复合成核剂不同组成对等规聚丙烯非等温结晶动力学及其熔融行为的影响。动力学分析结果表明莫志深方法很好地描述聚丙烯非等温结晶动力学,用Kissinger公式计算所得非等温结晶活化能表明复合成核剂的加入提高了结晶活化能。结晶形态和熔融行为均依赖于复合成核剂的组成和降温冷却速率,较低的降温速率有利于β晶型的生成,随着降温速率的增加,β晶型的相对含量减少。在较多的β成核剂含量和较低的降温速率条件下,可以获得较高含量的β晶型。

The nonisothermal crystallization kinetics and subsequent melting behavior of isotactic polypropylene（iPP） nucleated by α/β compounding nucleating agents（NAs） with different composition ratios of α nucleating agent,di（3,4-dimethyl）dibenzaldehyde sorbitol（DMDBS）,to β nucleating agent,rare earth（WBG）,were studied by differential scanning calorimetry（DSC）.It was found that the model proposed by Mo can successfully describe the nonisothermal crystallization kinetics of pure iPP and nucleated iPPs.The crystallization active energy of iPP and nucleated iPPs during nonisothermal crystallization was determined by Kissinger method,and results show that the addition of nucleating agent increases the crystallization activation energy.Crystalline structure and melting behavior of the nucleated iPPs are dependent on the composition ratio of α nucleating agent to β nucleating agent in the used compounding nucleating agents and on the cooling rate during crystallization.Lower cooling rate is favorable for the formation of β-phase crystals,and the relative content of β-phase crystals in nucleated iPPs decreases with increasing cooling rate in crystallization process.The nucleated iPP with higher proportion of β-phase crystals in it can be obtained by using α/β compounding nucleating agent with higher composition ratio of β nucleating agent and lower cooling rate.