聚丙烯釜内合金初生态树脂粒子研究

Investigation of Nascent Polypropylene In-Reactor Alloy Particles

针对Ziegler-Natta/茂金属复合催化剂基于Spheripol工艺制备的聚丙烯釜内合金的初生粒子中存在的两种外观形貌的粒子,采用红外光谱(FTIR)、核磁共振(NMR)、扫描电镜(SEM)、偏光显微镜(POM)、热分析(DSC)和力学性能测试等方法对白色和半透明的初生态树脂粒子进行了组成、结构和力学性能的比较研究。FTIR,NMR和SEM结果表明,两者外观形貌的差异主要是二段聚合中乙烯-丙烯共聚物的含量和分布不同。DSC和POM结果表明,乙烯-丙烯共聚物的存在使半透明粒子中聚丙烯的结晶速率高于白色粒子。力学性能测试结果表明,由于乙烯-丙烯共聚物含量少,白色粒子的冲击韧性明显低于半透明粒子,但拉伸强度和弯曲模量明显高于半透明粒子。并基于聚合工艺提出了两种初生粒子形成的可能机理。

Heterogeneous nascent particles were observed in a pilot product of polypropylene in-reactor alloy, which was poly-merized by Ziegler-Natta/Metallocene hybrid catalyst using Spheripol technology. Most of the particles in the product are trans lucent, and opaque particles were observed as well. The differences in morphology, composition, chain structure, thermal prop-erties and mechanical properties between these two kinds of particles were investigated by Fourier transform infrared spectrosco- py （FTIR）, nuclear magnetic resonance （NMR）, scanning electron microscopy （SEM）, polarized optical microscopy （POM）, and differential scanning calorimetry （DSC） techniques. The results of FTIR, NMR and SEM indicate that different morphology of these two different particles is caused by different content of ethylene-propylene copolymers. The results of DSC and POM showed that the translucent particles has higher crystallization rate than opaque particles due to the presence of ethylene-propyl-ene copolymers. The mechanical properties results showed that the impact resistance property of opaque particles is obviously lower than that of translucent particles, while its tensile strength and bending modulus are much higher than that of translucent particles. Based on the process of Spheripol technology, a preliminary explanation for the formation of different nascent PP in-re-actor alloy particles is proposed.