Effects of the copolymer microstructure on the morphology of polyethylene–poly(ethylene‐co‐α‐olefin) blends

The effects of the copolymer microstructure on the morphology evolution in polyethylene/poly(ethylene‐co‐α‐olefin) blends were investigated. Microscopy revealed that the melt‐phase morphology, inferred from the solid‐state morphologies of annealed and quenched samples, was strongly affected by the copolymer structure, that is, the branch content and branch length. Higher molecular weight α‐olefin comonomer residues and residue contents in the copolymers led to faster coarsening of the morphology. The molecular weight of the polyethylene and the copolymers affected the coarsening rates of the morphology, principally through its influence on the melt viscosity. The effects of the molecular weight were largely explained by the normalization of the coarsening rate data with respect to the thermal energy and zero‐shear‐rate viscosity. Thus, the effect of the molecular weight on the compatibility of the blends was much smaller than the effects of the branch length and branch number. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 965–973, 2004     

Design and Theoretical Study of Nickel Catalysts for Syndiotactic Polyolefins

A nickel catalyst was nodeled with ligand L^2,[NH=CH-CH=CH-0]^-,which should have potential use as a syndiotactic plyolefin catalyst,and the reaction mechanism was studied by theoretical calculations using the density functinal method at the B3LYP/LANL2MB level.The mechanism involves the formation of the intermediate [NiL^2Me]^ ,in which the metal occupies a T-shaped geometry.This intermediate has two possible structures with the methyl group trans either to the oxygen or to the nitrogen atom of L^2.The results show that both structures can lead to the desired product via similar reaction paths,A and B.Thus,the polymerization could be considered as taking place either with the alkyl group occupying the position trans to the Ni-0 or trans to the Ni-N bond in the catalyst.The polymerization process thus favors the catalysis of syndiotactic polyolefins.The syndiotactic synthesis effects could also be enhanced by varations in the ligand substituents.From energy considerations,we can conclude that it is more favorable for the methyl ttrans-O position to form a complex than to occupy the trans-N position.From bond length considerations,it is also more favoured for ethene to occupy the trans-O position than to occupy the trans-N position.     

马来酸酐与聚烯烃接枝产物的表征

综述了马来酸酐与聚烯烃接枝产物的多种表征手段，重点分析了纯化处理，化学滴定以及红外分析方法的表征原理，应用和改进方法。     

密胺树脂/硼酸锌双层包覆微胶囊化红磷的制备及其在阻燃聚烯烃中的应用

描述了采用密胺树脂和硼酸锌连续双层包覆微胶囊化红磷(MRP)的最新制备方法。采用红外光谱、电子能谱和透射电镜等分析手段对其进行了表征，并证实红磷已被完全包覆。实验数据表明：经包覆的MRP的热稳定性获得了明显改善，吸水率和磷化氢的发生量均大大减少。MRP作为阻燃助剂应用于聚烯烃阻燃材料表现出了良好的阻燃效果。实时红外和热失重测量以及扫描电镜观察表明：其阻燃机制是红磷受热时与树脂反应促进了含磷膨胀炭层的形成，从而提高了材料的热稳定性，碳层起到了隔氧、隔热作用，而且主要在凝聚相中发挥其阻燃作用。     

含硅功能化聚烯烃:合成及应用

聚烯烃功能化改性是获得高性价比新材料的有效途径。含硅功能化聚烯烃(SFPO)是聚烯烃分子结构中含有机硅功能基团或有机硅聚合物链段的一类功能化聚烯烃的统称。由于有机硅功能基团及有机硅聚合物特殊的理化性质,SFPO通常具有丰富反应性或优异性能,成为一类有代表性的功能化聚烯烃。SFPO可以作为反应性中间体,用于制备具有复杂拓扑结构的功能化聚烯烃(如星型聚合物、梳型聚合物、接枝共聚物)或聚烯烃共价键接枝改性纳米材料;SFPO还可作为功能性添加剂(如增容剂、加工助剂,表面改性剂),用于开发聚烯烃新材料。近年来,研究人员在含硅功能化聚烯烃研究领域取得了系列进展,本文旨在对相关工作进行系统总结,以期引起同行注意并促进相关研究深入发展。     

Copolymerization of Ethylene with 10-Undecen-1-ol Using Highly Active Vanadium(Ⅲ) Precatalysts Bearing Bis(imino)pyrrolyl Ligands

The copolymerizations of ethylene with 10-undecen-1-ol have been investigated using vanadium precatalysts, bis(imino)pyrrolyl vanadium(III) complexes 1-3, 2,5-C4H2N(CH=NR)2VCl2(THF)2 [R = C6H5(1), 2,6-iPr2C6H3(2), C6F5(3)], and the iminopyrrolyl and β-diketiminate ones for comparison. The polar monomer was pretreated by diethylaluminium chloride(present also as the cocatalyst) before the copolymerization. The monomer reactivity ratios were evaluated using the Fineman-Ross method. The ligand structure considerably influenced the catalytic activity and tolerance towards the polar monomer, the polar monomer incorporation and the molecular weights of the resultant copolymers. The bis(imino)pyrrolyl vanadium complexes exhibited promising catalytic performance for the copolymerization, and a high catalytic activity up to 3.84 kg/mmolv·h with a high comonomer incorporation of 14.0 mol% was achieved by complex 3 under mild conditions.     

Copolymerization of Ethylene with lO-Undecen-l-ol Using Highly Active Vanadium（III） Precatalysts Bearing Bis（imino）pyrrolyl Ligands

The copolymerizations of ethylene with 10-undecen-1-ol have been investigated using vanadium precatalysts, bis（imino）pyrrolyl vanadium（Ⅲ） complexes 1-3, 2,5-C4H2N（CH=NR）2VCl2（THF）2 [R = C6H5 （1）, 2,6-iPr2C6H3 （2）, C6F5 （3）], and the iminopyrrolyl and b-diketiminate ones for comparison. The polar monomer was pretreated by diethylaluminium chloride （present also as the cocatalyst） before the copolymerization. The monomer reactivity ratios were evaluated using the Fineman-Ross method. The ligand structure considerably influenced the catalytic activity and tolerance towards the polar monomer, the polar monomer incorporation and the molecular weights of the resultant copolymers. The bis（imino）pyrrolyl vanadium complexes exhibited promising catalytic performance for the copolymerization, and a high catalytic activity up to 3.84 kg/mmolv·h with a high comonomer incorporation of 14.0 mol% was achieved by complex 3 under mild conditions.     

步进扫描差示扫描量热法研究不同链结构的聚乙烯类聚烯烃热力学特性

采用步进扫描差示扫描量热法研究了几种具有不同链结构的聚乙烯类聚烯烃的热力学性质.结果表明,不同链结构的聚烯烃在热力学平衡熔融态下,其绝对比热容的温度依赖性在实验误差范围内几乎相同;而无论链结构的变化如何,在极低温度下稳定结晶态的热容也非常接近.但在熔融温度范围内,比热容对不同聚烯烃的链结构非常敏感,这是由于在远低于聚烯烃主熔化峰温度范围内,聚乙烯晶体结构中的不同支链的影响.在时间-热流的步进扫描曲线中,具有长支链结构的聚烯烃表现出独特的熔融-再结晶行为,这可能是由于交联点之间较长的受约束链段的运动在熔融过程中得到释放并重排所致.     

Synthesis and crystallization behavior study of syndiotactic polystyrene‐g‐isotactic polypropylene (sPS‐g‐iPP) graft copolymers

Based on coordination polymerization mechanism only, novel stereoregular graft copolymers with syndiotactic polystyrene main chain and isotactic polypropylene side chain (sPS‐g‐iPP) were synthesized via two steps of catalytic reactions. First, a chain transfer reaction was initiated by a chain transfer complex composed of a styrene derivative, 1,2‐bis(4‐vinylphenyl)ethane, and hydrogen in propylene polymerization mediated by rac‐Me₂Si[2‐Me‐4‐Ph(Ind)]₂ZrCl₂ and MAO, which gave iPP macromonomer bearing a terminal styryl group (iPP‐t‐St). Then the iPP‐t‐St macromonomers of varied molecular mass were engaged in syndiospecific styrene polymerization over a typical mono‐titanocene catalyst (CpTiCl₃/MAO) under different conditions to produce sPS‐g‐iPP graft copolymers of varied structure. With an effective purification process, well‐defined sPS‐g‐iPP copolymers were obtained, which were then subjected to differential scanning calorimetry (DSC) and polarized optical micrograph (POM) studies. The graft copolymers were generally found with dual melting and crystallization temperatures, which were ascribable respectively to the sPS backbone and iPP graft. However, it was revealed that the two segments displayed largely different melting and crystallization behaviors than sPS homopolymer and the precursory iPP‐t‐St macromonomer. Consequently, the graft copolymer exhibited much distinctive crystalline morphologies when compared with their individual components. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Gas chromatographic technique for determination of Irgafos 168 in polyolefin samples after conversion to the related phenolic compound by saponification

A gas chromatographic technique is reported for the determination of a secondary antioxidant, Irgafos 168, in polymeric samples. Irgafos 168 [tris(2,4-di-tert-butyl phenyl)phosphite] is extracted by dissolution/precipitation, saponified to 2,4-di-tert-butyl phenol by refluxing in the presence of methanolic potassium hydroxide, and determined by gas chromatography-flame ionization detection. The method’s repeatability is good, and the relative standard deviation is 7.5% (between runs) and 15.5% (between days). This method was applied to the determination of Irgafos 168 in commercial polymers, and the obtained results were in relatively good agreement with those obtained by the previously reported spectrophotometric method. Correspondence: Mir Ali Farajzadeh, Department of Chemistry, Faculty of Science, Urmia University, Urmia, Iran