Crystallization behavior of carbon nanofiber/linear low density polyethylene nanocomposites

Crystallization behavior of LLDPE nanocomposites is reported in the presence of three types of carbon nanofibers (CNFs) (MJ, PR‐19, and PR‐24). During nonisothermal crystallization studies, all three crystalline melting peaks for LLDPE matrix were observed in the presence of PR‐19 nanofibers (up to 15 wt % content), but only the high‐ and low‐temperature peaks were observed in the presence MJ nanofibers. The broad melting peak at low‐temperature became bigger, suggesting an increase in the relative content of thinner lamellae in the presence of MJ nanofibers. TEM results of nanocomposites revealed transcrystallinity of LLDPE on the surface of CNFs, and a slightly broader distribution of lamellar thickness. STEM studies revealed a rougher surface morphology of the MJ nanofibers relative to that of PR nanofibers. Also, BET studies confirmed a larger specific surface area of MJ nanofibers relative to that of PR nanofibers, suggesting that the larger and the rougher surface of MJ nanofibers contributes toward the different crystallization behavior of MJ/LLDPE nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

易开口、高透明线性低密度聚乙烯的研制与应用

采用助剂配方后改性的技术方法,研制开发出生产易开口、高透明线性低密度聚乙烯(LL-DPE)的助剂配方体系。考察了自主研发的增透剂、有机和无机开口剂等助剂的不同质量比对LLDPE膜的光学性能和开口性能的影响;并且在LLDPE装置上实现了工业化应用。     

Nanocomposites formed from linear low density polyethylene and organoclays

Polyethylene-clay nanocomposites were prepared by melt compounding various combinations of a maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA), a linear low density polyethylene (LLDPE), and two organoclays. The two types of organoclay were selected to show the effect of the number of alkyl groups attached to the nitrogen of the organic modifier on exfoliation and improvement of mechanical properties. Nanocomposites derived from the organoclay having two alkyl tails, M₂(HT)₂, exhibited better dispersion and improvement of mechanical properties than nanocomposites based on the organoclay having one alkyl tail M₃(HT)₁. This result is the opposite of what is observed for nylon-6 nanocomposites. In addition, the rheological properties and gas permeability of the nanocomposites derived from the organoclay having two alkyl tails, M₂(HT)₂ were investigated. Both melt viscosity and melt tension (melt strength) increased with increased content of clay (MMT) and LLDPE-g-MA. Gas permeability was decreased by the addition of MMT.     

Uniaxial orientation of linear low density polyethylene

Only a few reported studies have involved the uniaxial orientation of LDPE and even less on LLDPE. It is our purpose to report on characteristics of uniaxially oriented films of LLDPE that contribute to property development. The LLDPE has been coextruded at 25 and at 80°C layered as ribbons within longitudinally split billets of HDPE. The LLDPE so drawn was characterized by thermal analysis, birefringence, elastic recovery, and wide angle X-ray measurements. As a result, we can conclude that the drawing of LLDPE at the lower temperature produces a relatively high content of monoclinic crystals; the orientation behavior of LLDPE is similar to that of HDPE. The molecular network formed by entanglements and crystals reduces the draw to a maximum below 15.     

线性低密度聚乙烯/有机蒙脱土纳米复合材料的制备及性能研究

通过熔融共混法制备了线性低密度聚乙烯／有机蒙脱土（LLDPEtOMMT）纳米复合材料,采用X-射线衍射分析（XRD）和透射电镜（TEM）对材料的结构进行表征,研究了OMMT的用量对LLDPE／OMMT纳米复合材料力学性能及阻燃性能的影响。结果表明,当OMMT的用量为30％（重量百分比）8寸,材料的极限氧指数（LOI）从180％提高到23．8％,热释放速率峰值（PHRR）从LLDPE的771．9kW／m2下降到5113kW／m2,下降幅度高达33．8％,表现出较好的阻燃性能;同时材料也呈现出良好的力学性能。     

线性低密度聚乙烯催化剂研究新进展

综述了各种线性低密度聚乙烯(LLDPE)催化剂的国内外发展状况,包括茂金属催化剂、混合催化剂、非茂金属催化剂、双功能催化剂和后过渡金属催化剂等。     

线性低密度聚乙烯催化剂研究进展

综述了各种LLDPE催化剂的国内外发展状况，包括铬系催化剂、齐格勒-纳塔催化剂、茂金属催化剂、非茂金属催化剂、后过渡金属催化剂和复合催化剂等。     

Influence of carbon nanofiber structure on properties of linear low density polyethylene composites

Three types of carbon nanofibers (MJ, Pyrograf®III PR‐19 and PR‐24) were incorporated into linear low density polyethylene (LLDPE) using intensive mixing. The electrical volume resistivity of composites decreased with the addition of CNFs from over 10¹² Ω cm for pure LLDPE to less than 10⁴ Ω cm for carbon nanofibers (CNF) contents of 15 wt% or more. Tensile modulus increased from 110 MPa for pure LLDPE to 200 MPa and 300 MPa for 15 wt% MJ and 15 wt% PR composites, respectively. However, the tensile strength remained fairly unchanged at about 20 MPa. Strain‐to‐failure decreased from 690% for pure LLDPE to 460% and 120% for 15 wt% MJ and 15 wt% PR composites, respectively. It was inferred that the interfacial interactions of LLDPE matrix with MJ fibers is better than that with PR fibers, resulting from the rougher surface of MJ fibers. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Financial incentive of linear low density polyethylene blends

The key to successfully implementing polymer blends in end-use applications includes an understanding of performance requirements and the physical property balance of the blend, as well as the provision of financial incentive to the fabricator, The economic gain is calculated for two cases where blends were introduced to displace another material: a blend which gives higher productivity for blown film applications and a blend which allows for increased flow and a gage reduction for an injection molding application. As the resin cost usually accounts for more than seventy percent of the final product cost, the resin or blend cost affects the economic gain (if any) from the fabricator's point of view. Therefore, successful commercial implementation of a new resin or blend depends on its relative cost and benefit to other commercially available materials.     

开口剂在LLDPE中的应用

通过无机、有机、复配开口剂对线型低密度聚乙烯(LLDPE)爽滑、开口性能的改进研究发现,添加复配开口剂可使LLDPE薄膜获得理想的爽滑、开口性能,并在LLDPE装置上成功实现工业化生产,且生产平稳可控.工业化产品测试结果表明:LLDPE产品PE-l的熔体流动速率为2.0 g/10 min,拉伸屈服应力为10.20 MPa;薄膜雾度为28.1%,动摩擦系数为0.342,静摩擦系数为0.307,薄膜爽滑、开口性能得到大幅改进,满足质量指标要求.     

The effect of diameter on the mechanical properties of amorphous carbon fibres from linear low density polyethylene

Summary The mechanical properties of amorphous carbon fibres, derived from linear low density polyethylene strongly depend on the fibre diameter, which may be attributed to the presence of a skin/core structure in these fibres. High strength carbon fibres could thus be prepared by using thin precursor filaments, that are obtained by a melt-spinning process, in which the spinline is stretched at an elevated surrounding temperature. Careful carbonization of these precursors gives carbon fibres with a strength of 2.16 GPa, a modulus of 130 GPa and a high strain at break of 3%.     

线性茂金属专用树脂的生产及应用

介绍了大庆石化公司塑料厂线性装置生产茂金属聚乙烯树脂18X10D的生产过程,产品生产工艺条件、物性指标,并对树脂进行测试分析。通过加工、应用表明,该树脂具有优异的加工性和力学性能。用茂金属树脂生产的2m、9m两种棚膜,薄膜产品质量好,满足GB4455—2006和用户标准要求,可替代进口茂金属产品。     

Rheology of polycarbonate/linear low density polyethylene blends

The flow behavior of linear low density polyethylene blended with polycarbonate (LLDPE/PC) was studied at 245°C using an Instron Capillary Rheometer and a Rheometrics Mechanical Spectrometer. The capillary measurements were repeated several times for each crosshead speed and capillary. The averaged values were corrected for shear heating as well as the pressure, entrance-exit, and power-law fluid effects. In spite of the utmost care, blend results were erratic with a standard deviation of 25 to 35 percent. Analysis of the capillary data suggested a telescopic flow with the lower viscosity component of the blend migrating toward the capillary wall. The experimental difficulties resulted from the flow and time induced variations of blend morphology. By contrast, the dynamic shear test results were found to be rapid and reproducible with a standard deviation for the complex viscosity of blends not exceeding four percent. The shear moduli of blends indicated the presence of an apparent (time dependent) yield stress, originating from interaction between domains of the dispersed phase. At frequencies exceeding a critical value, shear coalescence of the dispersed phase was observed near the rim of the rheometer plates.     

茂金属线型低密度聚乙烯的结构与性能

利用傅里叶变换红外光谱、凝胶渗透色谱、差式扫描量热法和力学性能测量等手段表征了茂金属线型低密度聚乙烯(mLLDPE)和传统线型低密度聚乙烯(LLDPE)的结构及性能,用热分级法表征了LLDPE的片晶厚度多散性,测试了mLDPE薄膜的相关性能。结果发现,mLLDPE的片晶厚度分布指数为1.1347,小于传统LLDPE,表明其具有更好的支化均匀性,但其相对分子质量分布窄;mLLDPE薄膜具有较高的落镖冲击强度、撕裂强度、热封强度和突出的光学性能。     

Morphological responses in thermally conditioned linear low density polyethylene

An octene-modified linear low density polyethylene has been used to examine the mechanisms involved during thermal annealing. Annealing temperatures ranged from 60 to 100°C. Annealing results in crystallinity increments and these respond to two concurrent effects. One involves the segregation from crystalline regions of low molecular weight moieties in the polymer's molecular weight distribution; the other is lamellar thickening, leading to the formation of more highly perfected crystalline domains. In the present polymer, the two effects were found to be in balance at annealing temperatures near 80°C leading to the optimum distribution of crystalline regions in the amorphous portions of the polymer. The effect of thermal conditioning on mechanical properties of the polymer was illustrated in terms of the initial modulus and the polymer's yield strength. The twin mechanisms of molecular fractionation and lamellar thickening were found to influence both of the mechanical property parameters.     

Preparation of functionalized graphene/linear low density polyethylene composites by a solution mixing method

The surface modification of graphene as well as the characterization of modified graphene-based polymer composite prepared by solution mixing techniques was examined. X-ray photoelectron spectroscopy was employed to examine the surface modification and formation of graphene. The tensile strength of the composite increased with 3 wt.% of DA-G loading and was 46% higher than that of neat LLDPE. The onset thermal degradation temperature of the composite (3 wt.% of DA-G) was increased by ∼40 °C compared to neat LLDPE. A sharp increase in electrical conductivity of the composite was observed at 3 wt.% of DA-G content.     

Crystallization kinetics modeling of high density and linear low density polyethylene resins

This paper describes isothermal and nonisothermal crystallization kinetics of a Ziegler‐Natta catalyzed high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) resins. Standard techniques such as differential scanning calorimetry (DSC) and light depolarization microscopy (LDM) techniques were used to measure isothermal kinetics at low supercoolings. DSC was also used to measure nonisothermal crystallization kinetics at low cooling rates. Extrapolation of isothermal crystallization half‐times of Z‐N catalyzed LLDPE resin using the isothermal half‐time analysis led to erroneous predictions, possibly due to Z‐N LLDPE consisting of a mixture of molecules having different amounts of short chain branching (comonomer). However, predicted reciprocal half‐times at high supercoolings, using isothermal half‐time analysis and using nonlinear regression of nonisothermal crystallization kinetics measured at low cooling rates using the differential Nakamura model, of the HDPE were similar to measured reciprocal half times at high supercoolings of a similar HDPE by Patki and Phillips. It is also shown that the differential Nakamura model can be effectively used to model nonisothermal crystallization kinetics of HDPE resins. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

LLDPE与甲基丙烯酸接枝共聚

采用溶液聚合和悬浮聚合法研究了线型低密度聚乙烯对甲基丙烯酸的接枝行为，发现溶液接枝法的产物有较高的接枝率，对铝箔的粘合力很强。     

易加工LLDPE的性能及生产方法

介绍了易加工线型低密度聚乙烯(LLDPE)的性能特点。综述了制备易加工LLDPE的方法,包括:通过设计聚合催化剂生成具有长支链结构的LLDPE;通过控制聚合工艺或催化剂形成双峰或宽峰分布的LLDPE;通过后加工改性改善LLDPE的加工性能等。     

茂金属线性低密度聚乙烯树脂的结构与性能

对国产和进口茂金属线性低密度聚乙烯树脂(mLLDPE)的分子量及分布、支化程度、基本性能与流变行为进行了对比分析,研究表明国产mLLDPE与进口同类产品相比,分子量分布宽,支化程度高,加工性能更好,可以通过流变测试的各种参数如黏流活化能、剪切变稀指数、松弛谱分布宽度对其结构进行剖析。同时对两者薄膜制品的性能进行了研究,结果表明,国产mLLDPE树脂生产的薄膜力学性能更为优异,但鱼眼稍多,外观略差。