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综述了以硼化合物为助催化剂的离子茂金属催化剂催化丙烯聚合的研究进展,介绍了用不同催化体系制备的不同结构的聚丙烯的性能及用途,并对聚合机理进行了探讨 。 相似文献
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复合载体法制备聚丙烯-蒙脱土复合材料 总被引:3,自引:0,他引:3
将传统Z-N催化剂TiCl4负载于蒙脱土.乙醇镁复合载体上,进行丙烯常压原位聚合,制备聚丙烯-蒙脱土纳米复合材料,克服了单-蒙脱土作载体时聚合活性低、产物分子量小的缺点。对比不同制备过程的催化剂,发现TiCl4的后处理可以大幅提高催化活性。引入苯乙烯可有效降低Mg—MMT/Mg(OEt)2/TiCl4/EB体系制备的Cat5催化聚合时所需的Al/Cat比。由Mg—MMT/Mg(OEt)2/Ti(OBu)4/TiCl4/EB体系制备的Cat6具有活性高,所需Al/Cat低的优点,为合适的制备聚丙烯-蒙脱土纳米复合材料的催化剂。WAXS和TEM表明复合材料中蒙脱土主要呈剥离杰分散干聚丙烯基体中。产物的熔点和商用聚丙烯的熔点接近。 相似文献
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宽相对分子质量分布聚丙烯技术进展 总被引:5,自引:0,他引:5
介绍了相对分子质量分布对聚丙烯(PP)性能的影响以及加宽相对分子质量分布在PP新产品开发中的作用。通过改变聚合工艺或采用新型催化剂加宽PP的相对分子质量来克服普通PP刚性差、热变形温度低、熔体强度差的缺点,提高PP的性能,拓宽了PP应用领域。 相似文献
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张月秋 《现代塑料加工应用》2006,18(4):24-26
研究了M-donor-TK260催化剂体系与Hypol工艺生产装置上常用的DDS-TK260催化剂体系在丙烯聚合特性上的差别,并利用M-donor-TK260催化剂体系在中试装置上开发抗冲聚丙烯,对2种催化剂体系在中试生产上的差别和适应性进行了详细分析。试验表明,使用M-donor-TK260催化剂体系活性高,产品冲击性能优异,其可用在Hypol工艺装置上生产抗冲聚丙烯。 相似文献
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Javid Vaezi Mehdi Nekoomanesh Seyed Hassan Jafari Hartmut Komber Alireza Mojarrad 《Polymer-Plastics Technology and Engineering》2018,57(8):791-803
In this study, morphological and rheological characteristics of bimodal polypropylene reactor blends synthesized by binary catalysts based on I: rac-Me2Si(2-Me-4-PhInd)2ZrCl2 and II: (2-PhInd)2ZrCl2 at different molar ratios were investigated. Gel permeation chromatography, scanning electron microscopy, and rheometry analysis were performed to evaluate the effect of molar ratio of catalyst II, responsible for the formation of elastomeric stereoblock polypropylene with low molecular weight, to catalyst I, responsible for production of high molecular weight isotactic (i) polypropylene, on the molecular weight, molecular weight distribution, morphological characteristics and rheological behavior of the synthesized products. The gel permeation chromatography results indicated that once a hybrid of the two catalysts is used, a broad and bimodal molecular weight distribution would be obtained, and the molar ratio of the catalysts governs the values of molecular weight and molecular weight distribution. 13C NMR results suggest that the different polypropylene tacticity resulting from the two catalysts (stereoblock vs. isotactic) is hardly influenced using a binary system. The effect of molecular weight enhancement and molecular weight distribution broadening was confirmed through the linear rheological data (G′ at lower frequencies, crossover modulus and crossover frequency) due to the impeded molecular motions of chains with high molecular weights which play an important role in the elasticity of chains. The zero shear rate viscosity and relaxation time, determined by fitting the Carreau–Yasuda model, are in great conformity with the experimental data at low-frequency region. Likewise, the miscibility and increased level of heterogeneity of microstructure, which is a result of changing the molar ratios of catalysts II/I, are confirmed through the Cole–Cole and Han plots and were further corroborated through the obtained scanning electron microscopy results. 相似文献
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Javid Vaezi Mehdi Nekoomanesh Seyed Hassan Jafari Masoud Razavi Aghjeh 《Polymer-Plastics Technology and Engineering》2017,56(17):1898-1907
A homogenous binary metallocene catalytic system comprising of isospecific rac-Me2Si(2-Me-4-Ph In)2ZrCl2(I) producing high molecular weight isotactic polypropylene and oscillating (2-Ph In)2ZrCl2(II) precursor producing low isotactic elastomer polypropylene at three varying molar ratios of two types of catalysts was used to synthesize polypropylene reactor blends. Dynamic mechanical thermal analysis and rheological properties along with molecular weight of synthesized polypropylene reactor blends were studied and correlations among these properties were established. It was found that molar ratio of catalysts is a significant factor in determination of molecular weight and its distribution. The produced polymers with unimodal molecular weight distribution showed intermediate modulus during dynamic mechanical thermal experiment, while the ones with bimodal molecular weight distribution exhibited a kind of phase separation at low temperature. Depending on strength of the developed structures, determined by the presence of interfacial connectors, the modulus could be adjusted. Origins of other types of relaxations and their differences for each type of the developed products were discussed in detail. From rheological results and particularly the relaxation curves, the characteristics of the chain structure of the synthesized reactor blends could be resolved. It was revealed that one of the synthesized polymers had long chain branches unlike the rest of the samples having linear chain structure. 相似文献
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Blends of polypropylene homopolymer (PP) and metallocene produced ethylene‐octene copolymer (EOR) with a bimodal particle size distribution were investigated. The aim of the work was to study the influences of EOR characteristics and its concentration on the tensile and impact properties of the blends. The matrix ligament thickness between rubber particles was measured and compared to those predicted using the theoretical models. The relationships between blend morphology and impact property were reported. It was found that the content of comonomer and molecular weight of the EOR as well as its concentration in the blends were the major factors controlling the tensile and impact properties of the blends. These factors became ineffective to impact property when the ligament thickness of the matrix was larger than the critical value (T ~0.3–0.4 μm). To achieve blends of high impact strength, the ligament thickness between rubber particles should be smaller than the critical value, and for a certain ligament thickness, EOR with high octene content and high molecular weight was preferred. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2412–2418, 2002 相似文献
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Isotactic polypropylene blends with 0–20 vol % thermoplastic elastomers were prepared to study the influence of elastomer particle size on mechanical properties. Polystyrene-block-poly(ethene-co-but-1-ene)-block-polystyrene (SEBS) was used as thermoplastic elastomer. SEBS particle size, determined by means of transmission electron and atomic force microscopy, was varied by using polypropylene and SEBS of different molecular weight. With increasing polypropylene molecular weight and, consequently, melt viscosity and decreasing SEBS molecular weight, SEBS particle size decreases. Impact strength of pure polypropylene is almost independent of molecular weight, whereas impact strength of polypropylene blends increases strongly with increasing polypropylene molecular weight. The observed sharp brittle–tough transition is caused by micromechanical processes, mostly shear yielding, especially occurring below a critical interparticle distance. The interparticle distance is decreasing with decreasing SEBS particle size and increasing volume fraction. If the polypropylene matrix ligament between the SEBS particles is thinner than 0.27 μm, the blends become ductile. Stiffness and yield stress of polypropylene and polypropylene blends increase with increasing polypropylene molecular weight in the same extent, and are consequently only dependent on matrix properties and not on SEBS particle size. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1891–1901, 1998 相似文献
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超高分子量聚丙烯(UHMWPP)是一种黏均分子量百万以上,具有超高的强度、超高的耐磨性、较强的抗氧化能力的热塑性工程塑料,可用于制备高强度、高模量、耐腐蚀、抗冲击、耐应力开裂的聚丙烯产品。本工作的目的在于制备出分子量超过200万的聚丙烯,将其用作3D打印材料来解决由于分子链较长引起高熔体黏度和低流动性而导致加工难成型问题。本工作基于传统的Ziegler-Natta催化剂,对主催化剂进行金属离子和有机物的负载,通过控制丙烯的链转移来控制聚丙烯的分子量,并且在聚合反应过程中不加入氢气(带有活性氢的物质),以防止其成为聚合反应的终止剂。研究了聚合反应温度、聚合反应时间、助催化剂和外给电子体对聚丙烯分子量的影响。采用黏度法、升温淋洗分级法等表征了制备的聚丙烯分子量。通过聚合工艺优化,在聚合反应温度70℃、聚合反应时间60min、助催化剂三异丁基铝、外给电子体P Donor下,最终制备出了黏均分子量超过204万的超高分子量聚丙烯。 相似文献
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Using reactive extrusion, polypropylene is functionalized with maleic anhydride and compared on an equimolar basis to polypropylene that is functionalized with an asymmetric, carboxylic acid containing peroxide. The grafting efficiency for the asymmetric peroxide is double that obtained for the maleic anhydride system. Moreover, the asymmetric peroxide yields a functionalized material with minimal molecular weight degradation and desirable mechanical properties, relative to maleic anhydride‐grafted polypropylene. In compatibilized blends of polypropylene and nylon 6,6, the polypropylene that was functionalized with the asymmetric peroxide is found to be an improved compatibilizer compared to that of maleic anhydride‐grafted polypropylene. The differences in mechanical properties of the two different functionalized polypropylene materials and their respective blends are rationalized on the basis of the grafting efficiency, molecular weight degradation during reactive extrusion, and effect of free functional species on the ability to form graft copolymers in compatibilized blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2398–2407, 2001 相似文献
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Polymerization of propylene was carried out by using MgCl2.EtOH.TiCl4.DIBP.TEA.cHMDMS catalyst system in n‐heptane, where MgCl2, EtOH, TiCl4, DIBP (diisobutyl phthalate), TEA (triethyl aluminum), and cHMDMS (cyclohexyl methyl dimethoxy silane) were support, ethanol for alcoholation, catalyst, external donor, cocatalyst (activator), and internal donor, respectively. The catalyst activity and polymer isotacticity were studied by measuring the produced polymer and its solubility in boiling n‐heptane, respectively. The molecular weight and molecular weight distribution of the polymers were evaluated by gel permeation chromatography. Hydrogen was used for controlling the molecular weight. For producing the bimodal polypropylene, the polymerization was carried out in two steps (i.e., in the presence and absence of hydrogen). It was found that the catalyst showed high activity and stereoselectivity, on the other hand, bimodal polymer could simply be produced in two‐step polymerization by using MgCl2.EtOH.TiCl4.DIBP.TEA.cHMDMS catalyst system. Meanwhile, the effect of the step of the hydrogen adding on propylene polymerization was investigated. It was shown that the addition of hydrogen in the second step was more suitable. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1456–1462, 2006 相似文献
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The melt spinning of metallocene catalyzed isotactic polypropylene resins was investigated. The details are presented for on‐line studies performed on six miPP resins with melt flow rates (MFRs) between 10 and 100 and a Ziegler–Natta catalyzed isotactic polypropylene resin with a MFR of 35 for comparison. The on‐line studies indicated that, as the molecular weight and polydispersity increased, crystallization occurred closer to the spinneret at higher crystallization temperatures and under lower spin line stresses. Further, as the spinning speed increased, crystallization occurred closer to the spinneret at higher crystallization temperatures because of increased stress in the spin line. These observations were interpreted in terms of an increased rate of crystallization caused by increased molecular orientation in the spin line with increasing molecular weight and increasing spinning speed. This “stress‐enhanced” crystallization was further interpreted in terms of an increased rate of crystal nucleation. It was further concluded that the narrower molecular weight distribution of metallocene resins was the primary factor that produced differences in the structure and properties of fibers spun from these resins compared to those of Ziegler–Natta catalyzed resins of similar weight‐average molecular weight or MFR. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3223–3236, 2001 相似文献
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研究了水-聚丙二醇两相体系中生物转化法合成2-苯乙醇的工艺条件,考察了聚丙二醇分子量、加量、转化振荡转速和底物浓度对2-苯乙醇合成的影响,确定了最佳的转化条件. 结果表明,摇瓶中两相体系转化合成2-苯乙醇的最佳条件为:聚丙二醇分子量1500,加量为培养基体积的1/2,振荡转速250 r/min,底物浓度13 g/L. 在5 L发酵罐中采用水-聚丙二醇两相体系生物转化法合成2-苯乙醇,浓度达6.87 g/L,产率为0.38 g/(L×h),较常规水相转化分别提高了42.2%和58.3%. 相似文献