丙烯/1-丁烯无规共聚物的非等温结晶行为研究

本体聚合方法合成了丙烯/1-丁烯无规共聚物,用DSC研究了丙烯/1-丁烯无规共聚物的非等温结晶动力学行为。结果表明：用Jeziorny方法处理丙烯/1-丁烯无规共聚物的非等温结晶行为存在一定的局限性;用莫志深方法处理丙烯/1-丁烯无规共聚物的非等温结晶行为可行, F(T)值随相对结晶度的升高而增大,在相对结晶度相同的条件下,随1-丁烯含量的增加,共聚物的结晶速率降低,结晶变得困难;对于同一种样品,在不同结晶度下α值几乎不变,近似为一常数,这说明表观Avrami指数n与Ozawa指数m之间存在一定的比例关系。     

丙烯/1-丁烯无规共聚树脂等温结晶动力学研究

采用本体聚合方法合成了丙烯/1-丁烯无规共聚树脂,通过DSC研究了丙烯/1-丁烯无规共聚物的等温结晶动力学。根据Avrami方程求出了各个结晶温度下的结晶动力学参数K(T)、 n、t1/2,以及样品的结晶活化能。结果表明,随着结晶温度的升高,同一样品的结晶速率逐渐下降,说明样品的结晶是依热成核控制为主;Avrami指数 在3~4之间,表明共聚物晶体的生长方式为三维球状生长。在同一结晶温度条件下,随着共聚物中1-丁烯单元含量的增加,晶体的成核和结晶速率均下降,结晶活化能增加,共聚物中1-丁烯单元含量对结晶速率的影响很大。     

聚丙烯/乙丙抗冲共聚物合金结晶行为研究

实验室聚合得到乙烯单元含量分别为0.94 %、1.67 %、3.00 %(摩尔分数,下同)的聚丙烯/乙丙抗冲共聚物（PP/EPR）合金样品,用差示扫描量热法研究了样品的等温结晶和非等温结晶行为。实验结果表明,各样品在不同温度下的等温结晶均符合Avrami方程;同一样品,等温结晶温度越高,结晶所需要的时间就越长,结晶速率越低,非等温结晶时随着降温速率的增加,结晶温度范围变宽并向低温移动;对于不同样品,等温结晶的结晶速率随乙烯单元含量增加而降低,但当乙烯单元含量为3.00 %时出现相反的情况,非等温结晶时的结晶温度也有同样的规律。     

丙烯/丁烯-1共聚透明聚丙烯的生产开发

文章阐述了生产透明聚丙烯的方法。介绍了丙烯/丁烯-1共聚透明聚丙烯PPR-MT18-S的开发和生产过程,讨论了丙烯/丁烯-1无规共聚物与丙烯/乙烯无规共聚物物理性能比较,结果表明丙烯/丁烯-1无规共聚物更适合于食品或药品容器、器具。     

丙烯/1-丁烯共聚物/无机物复合材料的性能研究

用无水硫酸钙/二氧化硅复合无机物对丙烯/1-丁烯共聚物进行填充改性,研究了丙烯/1-丁烯共聚物/无机物复合材料的物理性能、结晶熔融性能.结果表明:与丙烯/1-丁烯共聚物相比,改性后复合材料的弯曲模量和维卡软化温度均升高,冲击强度和熔体流动速率均下降,注塑样品收缩率的各向异性减小,结晶峰温度和结晶起始温度均升高,结晶温度...     

聚丙烯装置抗冲共聚物结晶分析

本文对聚丙烯装置聚合得到的乙烯单元含量分别为0.85%、1.55%、2.7%的丙烯/乙烯抗冲共聚物样品,用DSC研究了样品的等温结晶行为,证明各样品在不同的温度下的等温结晶均符合Avrami方程。同一样品,等温结晶温度越高,结晶所需要的时间就越长,结晶速率越低。对不同样品,等温结晶的结晶速率随乙烯单元含量增加而降低,但当乙烯单元含量为2.7%和1.55%的两个样品出现相反的情况。     

用13C-NMR表征高乙烯含量乙烯-丙烯无规共聚物的结构与性能

采用淤浆聚合法,使用3种聚丙烯催化剂制备了高乙烯含量乙烯-丙烯无规共聚物,并采用核磁共振碳谱对共聚物结构和性能进行了表征。结果表明:在相同聚合条件下,使用二醇酯化合物作为内给电子体的ND催化剂同已商业化的两种Ziegler-Natta催化剂CAT1和CAT2聚合得到的乙烯-丙烯无规共聚物中的乙烯摩尔分数接近,为75%~78%;使用ND催化剂聚合得到的乙烯-丙烯无规共聚物链段中乙烯-丙烯单元序列分布更均匀;使用ND催化剂聚合得到的乙烯-丙烯无规共聚物中橡胶相相对含量高于采用CAT1和CAT2催化剂。     

偏氟乙烯－六氟丙烯共聚物溶剂浇铸膜的非等温结晶动力学行为

利用示差扫描量热法(DSC)研究偏氟乙烯-六氟丙烯(PVDF-HFP)共聚物溶剂成膜前后的非等温结晶动力学,结果表明,PVDF-HFP共聚物的结晶对降温速率有一定的依赖关系,成膜后的共聚物与成膜前的共聚物对比发现,成膜后的共聚物的结晶温度升高,结晶速率加快,结晶时间t1/2缩短.用Jeziomy法处理非等温结晶过程较理想.Jeziomy法求出的结晶指数n的值在3～4之间,成膜前后的结晶速率常数kc影响较小.n和kc随降温速度的增大而增大,并且成膜后的共聚物的n和kc大于加工前的树脂的n和kc.Kissinger方法计算的PVDF-HFP共聚物成膜前后的结晶活化能分别为119.97kJ/mol和168.29kJ/mol.     

1-丁烯-丙烯共聚物结构与性能研究

考察了1-丁烯-丙烯共聚物(B-P)的结晶性能、力学性能和流变行为,并与高全同聚1-丁烯(i-PB)进行了结构与性能的对比。结果表明:少量丙烯的引入,破坏了1-丁烯链段的规整排列,造成结晶度降低,力学性能下降。B-P的剪切速率增加到某一临界值时,材料内部结构发生改变,1-丁烯链段和丙烯链段同时开始运动,发生了剪切变稠,共聚物黏度变大,不易成膜。     

新型管材专用料聚1-丁烯基树脂结晶动力学研究

利用13C-NMR、POM(偏光显微镜)、DSC(差示扫描量热仪)对自制的聚1-丁烯(I-PB)及1-丁烯与少量丙烯共聚物(B-P)的组成、微观形态和结晶性能进行了研究.实验结果表明,该共聚物为嵌段共聚物,其中丙烯摩尔分数为6.4%;B-P的球晶尺寸与I-PB的球晶尺寸基本一致,但少量丙烯的引入改变了I-PB的结晶成核...     

Influences of copolymerization conditions on the structure and properties of isotactic polypropylene/ethylene–propylene random copolymer in situ blends

A spherical TiCl₄/MgCl₂‐based catalyst was used in the synthesis of in situ isotactic polypropylene/ethylene–propylene random copolymer blends by propylene bulk polymerization and subsequent gas‐phase copolymerization of ethylene with propylene. Different copolymerization conditions, such as the reaction time, monomer pressure, and composition, were investigated, and their influences on the structure and properties of the products were studied. Raising the monomer pressure was the most effective way of speeding up the copolymerization, but it caused more increases in the random copolymer than the block copolymer fractions. Increasing the ethylene content of the monomer feed also resulted in higher reaction rates and copolymer contents, but the ethylene contents of both the random and block copolymer fractions were also raised. In situ blends that contain more than 50 wt % copolymer were prepared. The mechanical properties of the blends, including the impact strength and flexural modulus, were regulated in a rather broad range with changes in the copolymerization conditions. The properties were highly dependent on the amount, distribution, and chain structure of the copolymer fractions. The impact strength was influenced by both the random copolymer and block copolymer portions in a complicated way, whereas the flexural modulus was mainly determined by the amount of random copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 445–453, 2002; DOI 10.1002/app.10415     

Lamellar morphology of random metallocene propylene copolymers studied by atomic force microscopy

Four sets of propylene based random copolymers with co-units of ethylene, 1-butene, 1-hexene and 1-octene, and a total defect content up to ∼9 mol% (including co-unit and other defects), were studied after rapid and isothermal crystallization. Etched film surfaces and ultramicrotomed plaques were imaged so as to enhance contrast and minimize catalyst and co-catalyst residues. While increasing concentration of structural irregularities breaks down spherulitic habits, the formation of the gamma polymorph has a profound effect on the lamellar morphology. Lamellae grown in the radial axis of the spherulite and branches hereon are replaced in γ-rich copolymers with a dense array of short lamellae transverse or tilted to the main structural growth axis. This is the expected orientation for γ iPP branching from α seeds. Spherulites are formed in copolymers with non-crystallizable units (1-hexene and 1-octene) up to ∼3 mol% total defect content and were observed up to ∼6 mol% in those with partially crystallizable comonomers (ethylene and 1-butene). However, lamellae were observed in all the copolymers analyzed, even in the most defective ones, highlighting the important role of the gamma polymorph in propagating lamellar crystallites in poly(propylenes) with a high concentration of defects. Long periods measured from AFM and SAXS are comparatively analyzed.     

丙烯/1-丁烯无规共聚透明聚丙烯研究

采用本体聚合方法合成了不同1-丁烯含量的丙烯/1-丁烯无规共聚透明聚丙烯,对其力学性能、透明性能及正己烷提取物含量进行了研究。试验表明当1-丁烯含量达到一定量时,丙烯/1-丁烯无规共聚透明聚丙烯与丙烯/乙烯无规共聚透明聚丙烯的透明性能相当,但前者综合力学性能更好,正己烷提取物更低,可广泛运用于食品包装行业。     

丙烯/1-丁烯聚合物合金的单体组成切换法制备：动力学及聚合器模型

采用球形负载型Ziegler-Natta催化剂和单体组成周期性切换的丙丁淤浆共聚合技术,原位制备了聚丙烯/丙丁共聚物合金。将共聚动力学的矩模型与物料衡算相结合,首次建立了单体组成切换的共聚反应器模型。依据实验所得的丙烯实时消耗速率拟合得到模型参数,并模拟计算了不同单体组成切换频率下的聚合反应活性和聚合产物的组成。结果表明,模型能很好地描述各切换频率下丙烯的聚合速率曲线、催化聚合活性,以及合金中1-丁烯的总含量、丙丁无规共聚物的含量和“嵌段”共聚物的含量等。结果还显示,共聚过程中丙烯的脉冲进料有利于提高单体向活性中心的扩散,进而提高聚合速率和聚合活性。     

Characterization of high melt strength propylene/1-butene copolymer synthesized by in situ heat induction melt reaction

Propylene/1-butene copolymer powders were produced through bulk copolymerization of propylene with 1-butene in a 12 m³ polymerization reactor. High melt strength polypropylene (HMSPP) was synthesized by in situ heat induction melt reaction, in which pure propylene/1-butene copolymer powders without any additives were used as a basic resin and trimethylolpropane triacrylate (TMPTA) as a crosslinking agent. The structure and properties of the resultant HMSPP were characterized by means of various measurements. The content of TMPTA strongly influenced the melt strength and melt flow rate (MFR) of HMSPP. With increasing the content of TMPTA, the melt strength of HMSPP increased, and the MFR reduced. In addition, owing to the existence of crosslinking structure, thermal stability and tensile strength of HMSPP were improved compared with pristine propylene/1-butene copolymer. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Influence of the longest ethylene and isotactic propylene sequences on crystallization elution fractionation of ethylene/propylene copolymers

Crystallization elution fractionation (CEF) is the newest crystallization-based technique for estimating the chemical composition distribution of ethylene/1-olefin copolymers. Understanding the separation mechanism of CEF for ethylene/propylene copolymers over their full compositional range is challenging because the crystallizabilities of the copolymer chains depend on the longest ethylene sequence and on longest isotactic propylene sequence. We developed a mathematical model to describe the CEF mechanism for ethylene/propylene copolymers over the entire compositional range using population balances for the crystallization and dissolution stages. The joint distribution of longest ethylene and isotactic propylene sequences determines how the copolymer populations crystallize and dissolve. The model was validated with experimental CEF profiles of ethylene/propylene copolymers varying from pure ethylene to propylene homopolymers.     

Comparative investigation on crystallization conditions dependence of polymorphs composition for β‐nucleated propylene/ethylene copolymer and propylene homopolymer

The crystallization conditions dependence of polymorphs composition in β nucleated propylene/ethylene copolymers (PPR) and propylene homopolymers (PPH) were comparatively investigated via wide angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) measurements. It is interesting to note that the amount of β form as a function of crystallization conditions presents an opposite trend for the β nucleated PPR and the β nucleated PPH under the conditions we investigated. For the β nucleated copolymers, the content of β form shows also an opposite tendency with that of γ form with the change of crystallization conditions. The formation of γ form is preferred under lower cooling rates or higher isothermal crystallization temperatures, whereas the amount of β form increased with increasing the cooling rates or decreasing the isothermal temperatures. This opposite tendency could be interpreted in terms of the competition between the β nucleation ability of β nucleating agent and the γ nucleation action of the comonomer defects. The existing comonomer defects that favor the formation of γ form may suppress the nucleation ability of β nucleating agent. A higher proportion of β form in PPR containing a β nucleating agent could be achieved under faster cooling rates or lower crystallization temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

茂金属催化乙丙共聚进展

综述了茂金属催化乙丙共聚的研究 ,包括乙丙共聚物的合成、表征、反应机理及工业化进展。着重介绍了茂金属催化乙丙共聚物的结构和性能的研究成果。