Crystallinity of Linear Low Density Polyethylene and of Blends with High Density Polyethylene

Blends of linear low density and high density polyethylene are examined by x-ray diffraction and differential scanning calorimetry in order to characterise the crystalline morphology and to investigate the compatibility of the polymers. The polymers are found to form a co-crystalline phase under a variety of conditions, and can thus be regarded as compatible. The lamellar distributions obtained from the differential scanning calorimetry melting thermograms are found to be dominated by the presence of the high density polyethylene, and this is attributed to the higher mobility of the high density molecules. The lattice parameters of the crystalline phases are found to increase with increasing side branch content.     

改性蛋白土填充线型低密度聚乙烯的研究

对超细加工并经硅烷偶联剂处理的蛋白土填充线型低密度聚乙烯进行了研究,结果表明:采用适当的偶联剂及恰当的添加量,改性蛋白土可以降低塑料的成本。     

利用高密度聚乙烯装置生产线型低密度聚乙烯的相关研究

随着我国经济实力的飞速发展,对线型低密度聚乙烯的需求也有了很大的提升,相关部门必须对高密度聚乙烯装置生产线型低密度聚乙烯工艺给予足够的重视,并且加大对催化剂的研究力度。因此,主要对高密度聚乙烯装置生产线型低密度聚乙烯工艺进行了简要分析,阐述了相关催化系统,并且对生产工艺装置与主要生产流程进行了研究分析。     

线性低密度聚乙烯的稳定性

本文阐述薄膜厚度、共混比例、熔体指数、稳定剂对LLDPE及LLDPE／LDPE共混物薄膜的光老化性、热稳定性和加工稳定性的影响。     

国内线性低密度聚乙烯现状

综述了国内线性低密度聚乙烯市场应用、生产情况、消费状况及技术进展情况,并提出了以后的发展建议。     

线性低密度聚乙烯抗静电性能研究

考虑到抗静电剂的析出因素,采用非离子型抗静电剂作为线性低密度聚乙烯(LLDPE)试验的主要助剂.研究了抗静电剂C在LLDPE中的析出速度和用量.结果表明:抗静电剂C质量分数不大于0.20%时,LLDPE短期和长期保持了较低的表面电阻率.     

Monte Carlo Analysis of Polydisperse Microparticle Impacts with Surfaces

The Monte Carlo method was applied to an impact model to investigate the impact of polydisperse microparticles with surfaces. The Monte Carlo results were compared to experiments. Two different situations were examined: the normal (90°) impact of microspheres with a molecularly-smooth silicon surface, and the oblique ( < 90°) impact of microspheres with a Formica surface. In the former, the percentage of microspheres captured by the surface and the overall capture velocity distribution were determined given the statistical distribution of the microsphere diameters. In the latter, both the Formica surface roughness angles and the diameters of the microspheres were treated as statistical variables. The mean values of the Monte Carlo simulation of the coefficient of restitution and the impulse ratio were found to agree with the data at the 95% confidence level. Finally, this approach was applied to model the impact of Lycopodium spores with a Formica surface.     

线型低密度聚乙烯的改性研究进展

综述了近几年线型低密度聚乙烯(LLDPE)的改性在力学、阻燃、电学、结晶等性能上取得的研究进展,并对未来LLDPE改性的研究方向进行了展望。     

茂金属线形低密度聚乙烯的热降解研究

研究了光敏剂钴化合物存在时茂金属催化剂和Ziegler—Natta催化剂生产的线形低密度聚乙烯(m—PE-LLD和PE—LLD)的热降解行为，测定了降解后产品的熔体流动速率、红外光谱和氧化诱导温度。结果表明：光敏剂使得加工过程中的降解反应增强，氧化诱导温度降低，氧化曲线形状发生改变；与PE—LLD相比，光敏剂对增强m—PE—LLD的降解反应和降低加工后样品的热稳定性的作用更强。     

Mathematical Model of the Separation of Polydisperse Systems

A mathematical model is proposed for the thin-layer separation of a polydisperse mixture. The specific features of the process that are due to the variation of the concentration and composition of the dispersed phase along the interplate channel are considered.     

Polyurethanes with Narrow‐ and Polydisperse Hard Segment Distributions

Polyurethanes with narrow‐disperse (ND) and polydisperse (PD) hard segment (HS) distributions were prepared in a two‐step process. First, a poly(propylene oxide) end‐capped with MDI (4,4′methylenebis(phenyl isocyanate) was synthesized. To this prepolymer either a diamine–diamide was added to form ND HSs or a mixture of a diamine–diamide and additional MDI to form PD HSs in the copolymers. The polyurethanes displayed a ribbon‐like crystalline morphology, and it was found that the copolymers with ND HSs were more crystalline, had a higher modulus, a less temperature‐dependant modulus, and a higher melting temperature than their PD counterparts. Overall, the polyurethanes with the narrow‐dispersed HSs displayed superior properties.

     

Calibration and Testing of Samplers with Dry,Polydisperse Latex

A new method for measuring the collection efficiency of an aerosol sampler as a function of particle size has been developed, featuring the use of dry, polydisperse latex particles. Test aerosol is generated by placing a polydisperse latex powder sample into a fluidized bed of glass beads. An Aerodynamic Particle Sizer (APS) measures the particle size distribution entering and leaving the sampler's size-selector, yielding the penetration efficiency. The use of dry latex minimizes the ''phantom'' particle problem inherent with the APS by avoiding the generation of high concentrations of small particles such as those produced by nebulizers. In addition to having useful properties for determining particle size cutoff characteristics, including spherical shape, near-unit density, and white color, latex particles afford a test for the presence of particle bounce and reen trainment. A complete efficiency measurement can be made in a little over three minutes, facilitating experimentation with parameters such as sampler flow rate, which require repeated measurements. The method has been used extensively for the development and calibration of respirable and PM-2.5 samplers.     

线型低密度聚乙烯抗静电母料的研究

研制了具有协同效应的复合抗静电剂配方,母料中抗静电剂含量为10%以上;使用该母料的专用料加工过程中不仅母料用量可减少,而且产品的加工工艺稳定;专用料的力学性能稳定。能使专用料表面电阻率(ρS)长短期都达到较低值的母粒用量为3.9%。     

硬球链流体在平板和硬球表面分布的密度泛函理论

采用Yethiraj和Woodward的密度泛函理论方法,结合胡英和刘洪来等发展的硬球链流体状态方程,得到了自由连接硬球链流体在平板狭缝中和球形固体颗粒表面附近的密度分布表达式,并计算了在两平行壁所组成的狭缝中和直径大小不同的球形固体颗粒周围硬球链分子的链节密度分布.理论计算结果与作者采用Dickman 和Hall 的方法进行Monte Carlo计算机模拟结果非常吻合.颗粒直径对链状分子的密度分布有一定的影响,随着固体颗粒直径的增加,靠近颗粒表面附近的链节密度降低.     

线性低密度聚乙烯超微薄膜的加工和应用

介绍了线性低密度聚乙烯超微薄膜的加工技术和应用情况。     

二溴新戊二醇在膨胀型阻燃PE-LLD中的作用

以二溴新戊二醇(DBNPG)作为碳源代替部分季戊四醇(PER), 以PER/DBNPG混合磷酸酯三聚氰胺甲醛树脂(MFR)微胶囊化聚磷酸铵(APP)合成膨胀型阻燃剂(IFR), 用于线形低密度聚乙烯(PE-LLD)阻燃。结果表明,适量的DBNPG可增强IFR与PE-LLD之间的相容性,改善材料的拉伸性能,提高材料熔体黏度,形成封闭的膨胀炭层;但DBNPG过量,IFR的软化温度降低,导致熔体黏度下降,破坏炭层的封闭性,恶化阻燃性能;当PER/DBNPG的质量比为70.0/115.5, 且PE-LLD/IFR的配比为70/30时,复合材料的阻燃性能达到最佳。     

Density and Moisture Profile Evolution during Timber Drying by CT Scanning Measurements

Timbers of 105 × 105 mm² in cross section and 1000 mm long were computed tomography (CT) scanned with a commercial unit in equal time steps during a drying cycle. The study aimed to convert the scanning numbers into wood density values, observe the changes that occur during the dehydration process, and, from these, differentiate moisture content as a function of time and space. The reference for calculating the moisture content of each image pixel was the oven-dry wood scan. Analysis of the results allowed visualizing the water distribution, the mechanism of water removal, as well as check formation. Although only a single drying run was analyzed and a limited number of timbers were scanned, the results revealed trends and thus show promise, so further research is urged because it may lead to a better understanding of water movement and check formation in wood during kiln drying.     

Density Profile of Small Glass Drops Chilled from the Liquid State and Subsequently Thermally Treated

The density profile was determined, from the surface to the core, of small soda-lime glass drops obtained by quenching in water from the liquid state. It was shown that, initially, the density increases from the surface to the inner layers but this trend is reversed at a certain distance from the surface, so that the density values found in the innermost layers are unusually low. Other investigations confirmed the existence of structural situations in the core different from those at the surface of each sphere. The quenched spheres were then heated at different temperatures for different times and the densities of the various layers were measured to determine the response of each zone to heat treatment after quenching. Some hypotheses are proposed to explain the results.