高分子分子量、分子量分布与熔体指数(MI)关系的研究(Ⅱ)──聚丙烯的分子量、分子量分布及熔体指数(MI)的实验考察

本文采用凝胶渗透色谱法（ＧＰＣ：ＷＡＴＥＲＳ－１５０Ｃ），对不同分子量、分子量分布和熔体指数的聚丙烯进行了测定，测定ＭＩ的样品近５０种，为验证本文第Ｉ部分提出的理论方程提供了相当充分的基础数据。从中发现齐格勒一纳塔催化剂的工业级聚丙烯的熔体指数范围可以很宽（０．５—１６ｇ／１０ｍｉｎ）。而重均分子量的范围大体上为２．５×１０５一３．５×１０５，数均分子量范围为２×１０４一６×１０４，从而使分子量分布分散系数（Ｍｗ／Ｍｎ）范围为４—１６。     

聚丙烯熔体流动指数测试与分析

在不同负荷和不同温度下,利用熔体流动速率仪测试聚丙烯的熔体流动指数,通过熔体流动指数这种非常简单的方法计算得到剪切应力、剪切速率、非牛顿指数、零切粘黏度和流动活化能等流变参数。     

高分子分子量、分子量分布与熔体指数（MI）关系的研究（Ⅰ）──熔体指数（MI）与分子量、分子量分布关系的理论模型及关联式

本文考察了有关零剪切速率下高聚物熔体粘度与分子量、分子量分布及星形支化结构之间关系，用应力张量，高分子链间缠结数目及分子量变化率之间的自相似变化模型理论，推导了一个普适方程，用来关联熔体指数（ＭＩ）与分子量（Ｍｗ），分子量分布（）及Ｍａｒｋ－Ｈｏｕｗｉｎｋ常数之间关系，为进一步研究和验证提供了理论依据。     

高分子分子量、分子量分布与熔体指数（MI）关系的研究（Ⅲ） 熔体指数（MI）分子量、分子量分布关联式的进一步考察及实验验证

本文在前两篇的基础上用实验数据验证理论公式。结果表明ｌｏｇＭＩ与－ＢｌｏｇＭｗ之间有较好的线性关系。但本文从另一拓扑几何排列组合理论角度推导了文献上尚未出现的新公式，同样也用实验数据来加以验证，其结果表明ｌｏｇＭＩ与－ＢｌｏｇＭｗ之间的线性关系优于前一种关系。     

间歇式聚丙烯装置产品熔体流动指数的控制

针对间歇式液相本体法聚丙烯装置的生产特点,根据实际生产经验,从原料、催化剂的选择与配方、升温操作、氢调、设备维护等对如何控制聚丙烯粉料熔体流动指数进行了分析。结果表明:只要控制得当,间歇式聚丙烯装置产品的熔体流动指数可以控制在(n±1.5)g/10min(n为预定值)的稳定范围。     

高分子分了阳,分子量分布与熔体指数（MI）关系的研究（III）：熔体指数（MI）…

本文在前两篇的基础上用实验数据验证理论公式。结果表明ｌｏｇＭＩ与－ＢｌｏｇＭｗ＋ＣｌｏｇＭｗ／Ｍｎ之间有较好的线性关系，但本文从另一拓扑几何排列组合理论角度推导了文献上尚未出现的新公式，同样也用实验数据来加以验证，其结果表明ｌｏｇＭＩ与－ＢｌｏｇＭｗ＋ＣＭｗ／Ｍｎ之间的线性关系优于前一种关系。     

分子量调节剂改善共聚聚丙烯熔体的流动性

通过采用添加分子量调节的方法调节共聚聚丙烯的熔体流动性,同时考察了抗氧剂等助剂对体系的影响。     

Effects of molecular weight and molecular weight distribution on creep properties of polypropylene homopolymer

The molecular weights of the industrial-grade isotactic polypropylene (i-PP) homopolymers samples were determined by the melt-state rheological method and effects of molecular weight and molecular weight distribution on solid and melt state creep properties were investigated in detail. The melt-state creep test results showed that the creep resistance of the samples increased by M_w due to the increased chain entanglements, while variations in the polydispersity index (PDI) values did not cause a considerable change in the creep strain values. Moreover, the solid-state creep test results showed that creep strain values increased by M_w and PDI due to the decreasing amount of crystalline structure in the polymer. The results also showed that the amount of crystalline segment was more effective than chain entanglements that were caused by long polymer chains on the creep resistance of the polymers. Modeling the solid-state viscoelastic structure of the samples by the Burger model revealed that the weight of the viscous strain in the total creep strain increased with M_w and PDI, which meant that the differences in the creep strain values of the samples would be more pronounced at extended periods of time.     

Do molecular weight determinations of coal-derived materials give meaningful answers?

The relation between number-average (M?_n) and weight-average (M?_w) molecular weights has been examined, and it was demonstrated how this can be employed to determine the self-consistency of results obtained for calculating molecular weights of chemically treated coals. The present method of calculation was calibrated against data of Katz et al., then applied to the data of Sun and Burk for g.p.c. fractions of alkylated coals. The newly calculated value for M?_w (3300) did not agree with Sun and Burk's value of 7882.     

Influence of molecular weight distribution on flow properties of commercial polyolefins

The aim of this work is to investigate the effects of molecular weight distribution on some conventional flow properties of polyolefins like melt flow index, melt flow ratio, and power law index. The study is designed in two steps. First, the statistical correlation analysis was carried out for proper choice of input variables for each output property and to find the most relevant mathematical forms of the considered parameters for the modeling section. Then the considered property was correlated to the entire molecular weight distribution using spline functions. The best fit was achieved by variation of the number of spline nodes and their values. The proposed methodology is able to be coupled with a polymerization model to correlate the polymerization conditions to the final properties of the product and design a polymerization control loop. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

新型高流动聚丙烯注塑专用料分子量及流变性能研究

对由聚合得到的新型高流动聚丙烯注塑专用料M#的热稳定性、分子量及流动性进行了系统的表征,井与国外样品AP03B和M1600进行了比较.结果表明;M#和AP03B、M1600的热稳定性相似,起始分解温度304℃,最大热失重温度458℃.重均分子量及分子量分布的大小顺序为:M#＞AP03B＞M1600.熔体流动速军(MFR)大小顺序为AP03B＞M1600＞M#.在高温下,剪切速率(γ)将对M#的加工性能有较大影响.     

Correlations of single-point parameters of linear rheology and molecular weight distribution of polypropylene homo- and copolymers

For various purposes, it is required to compress the shape of the molecular weight distribution (MWD) of polymers into a limited set of parameters. With increasing molecular weight and polydispersity, the MWD data obtained from chromatography become increasingly unreliable due to deficiencies in the high molecular weight region, making estimation via melt rheology more preferable. A number of empirical parameters obtained from melt rheology can be related back to MWD parameters. The target of this study is to establish the reliability of such relations for polypropylene homo- and copolymers. It is found that correlations between polydispersity from rheological crossover modulus and polydispersity via chromatography are not always valid. Therefore, the range of applicability must be kept in mind when attempting predictions based on these correlations because rheological measurements are sensitive to molecular characteristics in ways different from chromatography. The use of a modified polydispersity index is shown to be more reliable.     

低熔指透明聚丙烯注塑专用料T40B的开发

采用单环管工艺均聚法,通过对前期调研和多次试验筛选,选用合适的新型成核剂,并针对大庆石化聚丙烯装置的具体情况,研制开发出光泽度好、透明度高、低指数的高品质透明聚丙烯注塑专用料,各项指标符合要求,产品应用效果良好,达到了预期目的.     

Production and characterization of polypropylene fiber upon addition of selective peroxide during melt spinning and comparison with conventional polypropylene fibers

In the present work, effect of selective peroxide on reactor grade polypropylene (PP) (known as V30S) during melt spinning process on the physical and thermal properties of as‐spun resultant multifilament yarn was studied. Attempts have also been made to compare this yarn sample with other fiber samples produced from reactor and controlled rheology grades polypropylene. The results show that the multifilament yarn spun from V30S/Peroxide sample shows higher birefringence and tensile strength and also lower modulus, elongation at break, and shrinkage compared with that of spun from pure V30S granule. Density and thermal behavior studies show low variations compared with original sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

High molecular weight polypropylene nanospheres: Synthesis and characterization

The high molecular weight (MW) polypropylene with average particle size of 60 nm was synthesized by controlled growth mechanism using Ziegler–Natta catalyst. The atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that PP nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through Fourier transform infrared spectroscopy and X‐ray diffraction, respectively. It shows nanospherical PP particles with more crystallinity (～ 75%) compared with macrosized PP (～ 59%). In addition, differential scanning calorimetry studies revealed the finite particle size effect on T_g and the scale dependence T_g followed a first order exponential trend. As particle size goes down to nano‐ scale from macrosize, continuous elevation of T_g's were observed from ?25 to ?11°C. This phenomenon was directed to configuration entropy of single spherical nanoparticles of PP. The mechanical properties and surface roughness were also evaluated through AFM. At last, the properties of nanosized PP were compared with micron and macrosized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Rheological properties of polypropylenes with different molecular weight distribution characteristics

Relationships between the rheological properties and the molecular weight distribution of two polypropylene series with different molecular weight distribution characteristics were studied. The end correction coefficient in capillary flow is determined by the molecular weight M_w and the molecular weight distribution M_w/M_n, and is higher as both characteristic values are larger. The die swell ratio at a constant shear rate depends on M_w, M_w/M_n, and M_z/M_w, and is higher as the three characteristic values are larger. The critical shear rate at which a melt fracture begins to occurs depends on the molecular weight M_w and the molecular weight distribution M_z/M_w, and is proportional to M_z/M_w² in a log–log plot. The critical shear stress does not depend on the molecular weight, and is higher as M_z/M_w is higher. The zero‐shear viscosity is determined by a molecular weight of slightly higher order than M_w, and the characteristic relaxation time is determined by M_z. The storage modulus at a constant loss modulus scarcely depends on the molecular weight, and is higher as the molecular weight distribution M_w/M_n is higher. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2128–2141, 2002