三元无规共聚聚丙烯的结晶行为及其对热封性能的影响  

Crystallization behavior of polypropylene terpolymer and its effect on the thermal-sealing properties

作　　者：郭晓帅 Guo Xiaoshuai(Sinopec Ningbo New Materials Research Institute Co.,Ltd.)

机构地区：[1]中石化宁波新材料研究院有限公司

出　　处：《塑料包装》2023年第3期39-46,共8页Plastics Packaging

摘　　要：借助差示扫描量热法(DSC)、偏光显微镜(POM)、X射线衍射(XRD)等表征手段,分析了流延聚丙烯薄膜(CPP)热封层专用三元无规共聚聚丙烯的结晶行为。结果表明,三元共聚物的熔点低,结晶度低;对比不同的三元产品,进口产品新加坡TPCFL7632熔限宽,低熔点组分更多,同时具有少量的高熔点组分。连续自成核退火实验也表明FL7632具有较宽的等规度分布。三元PP中,α晶与γ晶共存,且较均聚PP,α晶体结构的内部分子排列较为松散,晶格存在膨胀现象。从结晶动力学结果来看,三元产品的生长维数(Avrami指数(n))n小于3,表明晶体的空间生长存在一定受限行为(表明晶体在三维空间的生长受到了一定的限制)。同时,FL7632结晶速度最快,这与其存在高熔点组分易成核有关。POM结果表明,FL7632的晶体形态为长条形晶体,这是由于其生成了大量的γ晶体,γ晶体的产生与FL7632分子链的无规度更高,等规链段长度短有关。FL7632独特的结晶行为与结晶形貌赋予了该产品优异的热封性能与力学性能。The crystallization behavior of polypropylene terpolymer for the thermal-sealing layer of cast polypropylene film(CPP)was investigated by differential scanning calorimetry(DSC),polarized-light optical microscope(POM)and X-ray diffraction(XRD).The results show that the terpolymer has a low melting point and a low degree of crystallinity.Compared with other ternary products,the imported prod uct Singapore TPC FL7632 has a wider melting temperature range and a higher content of components with low melting point.Also,it has a small amount of high melting point components.Successive self-nucleation and annealing experiments also indicate that the FL7632 has a wide isotacticity distribution.It is confirmed that theαcrystal andγcrystal coexistence in the ternary product.And compared with homopolymer PP,the internal molecular arrangement in theαcrystal is more loosen,with the lattice expansion phenomenon.From the results of crystallizatio n kinetics,the Avrami exponent(n)of the ternary product is less than 3,indicating that the growth of crystals in three-dimensional space is subject to certain limitations.Meanwhile,FL7632 has the fastest crystallization rate,which is related to the presence of high melting point components that are prone to nucleation.The POM results indicate that the strip crystals are observed in FL7632,which is due to the generation of a large number ofγcrystals.The generation ofγcrystals is related to the higher irregularity of FL7632 molecular chains and the length of isotactic segments.The unique crystallization behavior and morphology of FL7632 endow the product with excellent thermal-sealing and mechanical properties.

关 键 词：流延聚丙烯薄膜 三元无规共聚聚丙烯 结晶行为 热封性能 

分 类 号：TQ325.14[化学工程—合成树脂塑料工业]