线型低密度聚乙烯模压法高发泡塑料的研究

本文研究了用模压法制备线型低密度聚乙烯泡沫塑料的方法,系统地探讨了发泡剂、交联剂、促进剂、及润滑剂对泡沫性能的影响。试验结果表明,在适当的工艺条件下,熔体流动速率为2的线型低密度聚乙烯可以制得厚度为50mm、性能稳定的高发泡塑料,其表观密度可达到50kg/m~3,拉伸强度2.0MPa,断裂伸长率180%,压缩强度(压缩50%)0.15MPa,比相同条件下制得的低密度聚乙烯泡沫塑料的性能优越。     

纳米氧化锌/低密度聚乙烯复合材料性能的研究

研究了纳米氧化锌 低密度聚乙烯复合材料的拉伸性能,耐光老化性能及不同的加工方式对复合材料力学性能的影响。     

PVC／LLDPE共混物研究

本文探讨了改进聚乙烯/线形低密度聚乙烯机械性能的方法,以作为再加工聚合物废料包括混合物的方法,发现氯化聚乙烯是提高此类共混物拉伸强度和加工性能的有效添加剂,亦发现化学法或辐射法共交联能提高强度和刚性.     

低密度聚乙烯对聚苯醚合金性能的影响

研究了低密度聚乙烯(LDPE)对聚苯醚(PPE)合金的力学性能、外观、成型加工等方面的影响.研究发现,适量低密度聚乙烯的加入明显改善了聚苯醚合金的性能,体系的缺口冲击强度明显提高,样条表观光滑,成型加工条件得到改善,且体系相容性良好.     

LLDPE通讯电缆护套料DFH 2076的开发

介绍了在全密度聚乙烯装置上生产线型低密度聚乙烯通讯电缆护套料DFH 2076的生产技术,并对DFH 2076、进口料以及改性国产料的性能进行了比较.DFH 2076的熔体流动指数为(0.8±0.2)g/10 min,密度为(0.920±0.002)g/cm3,断裂拉伸强度大于或等于14.0 MPa,屈服拉伸强度大于或等于11.0 MPa,断裂伸长率大于或等于600%.经用户使用证明,DFH 2076加工性能良好,加工温度比进口料低10℃,挤出电缆稳定光滑.     

高透明薄膜用中密度聚乙烯

<正>据"www.ptonline.com"报道,美国Houston的埃克森美孚化工推出了新型中密度聚乙烯MPE35-05CH,低密度聚乙烯(LDPE)和线性低密度聚乙烯(LLDPE)在挤出设备上加工时显示出了优异加工性,且拉伸的薄膜薄。MPE35-05CH密度为0.935g/cm3,熔体流动速率为0.5g/10min。这种新型中密度聚乙烯为含己烯共聚物,具     

纳米氧化锌改性聚乙烯的研究

研究了不同种类的分散剂对低密度聚乙烯/纳米氧化锌复合材料的拉伸性能、耐光老化性能的改进及不同的加工方式对复合材料力学性能的影响。实验结果表明:可使用硬脂酸锌作为分散剂,与其他物质配合,保证一定的量,将纳米氧化锌直接添加进低密度聚乙烯中可使复合材料表现良好的综合性能。     

高强度薄膜专用HDPE的生产

在全密度聚乙烯装置上采用Unipol气相法工艺,以1-丁烯为共聚单体生产高强度薄膜专用高密度聚乙烯(HDPE)DGDB6097。DGDB6097的熔体流动速率(负荷21.6 kg)为7.00~13.00 g/10 min,密度为0.945~0.951g/cm3,拉伸屈服应力大于或等于19 MPa,拉伸断裂应力大于或等于23 MPa,断裂标称应变大于或等于500%。与相同工艺生产的普通薄膜专用线型低密度聚乙烯相比,DGDB6097的密度高、拉伸强度大;与国内市场常见的高强度薄膜专用HDPE DGDA6098相比,DGDB6097的力学性能、结晶性能、相对分子质量及其分布以及其薄膜的各项性能相当。加工应用表明,DGDB6097的加工性能和薄膜力学性能均满足用户要求。     

LDPE/LLDPE共混物的流变特征

本文对由三种牌号的线性低密度聚乙烯和一种牌号的低密度聚乙烯组成的三种不同类型的共混物的非等温拉伸流动和剪切流动行为进行了流变学研究。另外获得了挤出物胀大观象、毛细管流动中的不稳定升高和熔融态的张力行为方面的曲线和数据。     

两种国产挤出级聚乙烯的流变性质

聚乙烯树脂产量大,用途广。研究聚乙烯的流动特性。将促进其加工和应用的发展。成都科技大学林师沛等选用两种国产挤出级的高、低密度聚乙烯为对象,对粘性流动,出模膨胀和不稳定流动进行了研究。 试验结果表明:在粘性流动中,低密度聚乙烯的粘度对     

Rheology of LLDPE,LDPE and LLDPE/LDPE blends and its relevance to the film blowing process

The relevance of polymer melt rheology in film blowing process for linear low‐density polyethylene (LLDPE) and its blends with three different low‐density polyethylenes (LDPEs) has been discussed. The effect of different LDPE components as well as their concentration on shear and elongational viscosity has been investigated. A good correlation has been observed between the extensional rheological parameters of LDPEs measured by different experimental techniques. The molecular structure of parent polymers as well as blend composition play an important role in the rheology of these blends and consequently their performance in the film blowing process. © 2000 Society of Chemical Industry     

BMDPE／LDPE／LLDPE共混熔体的流变行为与力学性能

研究了双峰中密度聚乙烯（BMDPE），低密度聚乙烯（LDPE）与线型低密度聚乙烯（LLDPE）共混熔体的流变行为和力学性能，讨论了共混物的组成，剪切应力和剪切速率以及温度对熔体流变行为，熔体粘度和膨胀比的影响，测定了不同配比熔体的非牛顿指数，熔体流动速率，粘流活性能及屈服应力，断裂应力和断裂伸长率，为BMDPE的加工和使用以及开发高性能价格比的PE材料提供了依据。     

LLDPE/LDPE blends. I. Rheological,thermal, and mechanical properties

Structure and mechanical properties were studied for the binary blends of a linear low density polyethylene (LLDPE) (ethylene‐1‐hexene copolymer; density = 900 kg m⁻³) with narrow short chain branching distribution and a low density polyethylene (LDPE) which is characterized by the long chain branches. It was found by the rheological measurements that the LLDPE and the LDPE are miscible in the molten state. The steady‐state rheological properties of the blends can be predicted using oscillatory shear moduli. Furthermore, the crystallization temperature of LDPE is higher than that of the LLDPE and is found to act as a nucleating agent for the crystallization of the LLDPE. Consequently, the melting temperature, degree of crystallinity, and hardness of the blend increase rapidly with increases in the LDPE content in the blend, even though the amount of the LDPE in the blend is small. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3153–3159, 1999     

硅烷交联聚乙烯电力电缆绝缘料的研制

采用两步法制备了硅烷交联聚乙烯（PE）电力电缆绝缘料。以双螺杆挤出机为反应器,以低密度聚乙烯（LDPE）和线型低密度聚乙烯（LLDPE）为基础树脂,考察了影响PE接枝交联的主要因素（如基础树脂的配比,交联剂的用量及种类,引发剂、抗氧剂的用量等）,得出了具有良好性能的硅烷交联PE电力电缆绝缘料的配方（质量份数）：LDPE为85．00phr,LLDPE为15．0H0phr,硅烷W为0．60phr,硅烷Q为1．40phr,引发剂为0．12phr,抗氧剂为0．20phr。     

LLDPE/LDPE/TiO2复合膜的分散及光学性能

讨论了纳米TiO2在线型低密度聚乙烯（LLDPE），低密度聚乙烯（LDPE）复合体系中的分散和体系流变行为，研究了复合薄膜的光学性能。结果表明，以高流动性LDPE为基体的纳米TiO2母料，加入LLDPE，LDPE体系中后。复合体系的表观粘度有所提高。但拉伸粘度显著下降。纳米TiO2母料在LLDPE／LDPE复合体系中具有良好的分散性，复合薄膜中的纳米TiO2为一次粒子。纳米TiO2起到了异相成核剂的作用。球晶的粒子得到细化。在本研究的纳米填充范围内（质量分数不大于1.0％），复合薄膜的透光度基本不变。雾度发生了较大幅度上升，复合薄膜在紫外光区域的吸收显著增强。     

Development of nanofibrous morphology in LDPE/LLDPE/PP blends and its effect on mechanical properties of blend films

Nanofibrous morphology has been observed in ternary blends of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and isotactic polypropylene (PP) when these were melt‐extruded via slit die followed by hot stretching. The morphology was dependent on the concentration of the component polymers in ternary blend LDPE/LLDPE/PP. The films were characterized by wide angle X‐ray diffraction (XRD), scanning electron microscopy (SEM), and testing of mechanical properties. The XRD patterns reveal that the β phase of PP is obtained in the as‐stretched nanofibrillar composites, whose concentration decreases with the increase of LLDPE concentration. The presence of PP nanofibrils shows significant nucleation ability for crystallization of LDPE/LLDPE blend. The SEM observations of etched samples show an isotropic blend of LDPE and LLDPE reinforced with more or less randomly distributed and well‐defined nanofibrils of PP, which were generated in situ. The tensile modulus and strength of LDPE/LLDPE/PP blends were significantly enhanced in the machine direction than in the transverse direction with increasing LLDPE concentration. The ultimate elongation increased with increasing LLDPE concentration, and there was a critical LLDPE concentration above which it increased considerably. There was a dramatic increase in the falling dart impact strength for films obtained by blow extrusion of these blends. These impressive mechanical properties of extruded samples can be explained on the basis of the formation of PP nanofibrils with high aspect ratio (at least 10), which imparted reinforcement to the LDPE/LLDPE blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Melt strength and film bubble instability of LLDPE/LDPE blends

The relevance of measuring the melt strength of low density polyethylene (LDPE), linear low density polyethylene (LLDPE) and their blends to their performance in terms of bubble stability in the film blowing process has been investigated. A good correlation between the melt strength values for two series of LLDPE/LDPE blends and the size of the operating window for stable film bubble formation has been established. Both the macromolecular structure of the parent polymers, and melt morphology play an important role in the performance of these blends in the film blowing process. © 1999 Society of Chemical Industry     

Rheological Properties of Different Film Blowing Polyethylene Samples Under Shear and Elongational Flow

Summary: The rheological behavior of polyethylenes is mainly dominated by the molecular weight, the molecular weight distribution and by the type, the amount and the distribution of the chain branches. In this work a linear metallocene catalyzed polyethylene (m‐PE), a branched metallocene catalyzed polyethylene (m‐bPE), a conventional linear low density polyethylene (LLDPE) and a low density polyethylene (LDPE) have been investigated in order to compare their rheological behavior in shear and in elongational flow. The four samples have similar melt flow index and in particular a value typical of film blowing grade. The melt viscosity has been studied both in shear and in isothermal and non‐isothermal elongational flow. The most important features of the results are that in shear flow the m‐PE sample shows less pronounced non Newtonian behavior while in the elongational flow the behavior of m‐PE is very similar to that of the linear low density polyethylene: the narrower molecular weight distribution and the better homogeneity of the branching distribution are reasonably responsible for this behavior. Of course the most pronounced non‐linear behavior is shown, as expected, by the LDPE sample and by the branched metallocene sample. This similar behavior has to be attributed to the presence of branching. Similar comments hold in non‐isothermal elongational flow; the LDPE sample shows the highest values of the melt strength and the other two samples show very similar values. As for the breaking stretching ratio the opposite is true for LDPE while m‐PE and LLDPE show higher values. The transient isothermal elongational viscosity curves show that the branched samples show a strain hardening effect, while LLDPE and m‐PE samples present a linear behavior.

Dimensionless flow curves of different polyethylene samples.     

应力集中效应对熔体挤出流动不稳定性的影响

用双毛细管流变仪研究了线型低密度聚乙烯、低密度聚乙烯及其共混物在较宽速率范围内的流变行为,通过分析流场中应力集中效应与不稳定流动的关系,从而控制不稳定流动现象。结果表明:挤出物在口模入口处的应力集中占总压力的15%以上时,一般导致毛细管人口压力降的无规振荡及挤出物的整体无规则波动和破裂;整条毛细管上的挤出压力发生振荡,挤出物外观发生光滑段和粗糙段交替出现的有规畸变。     

Elongational flow properties of low-density polyethylene and linear low-density polyethylene from nonisothermal melt spinning experiments

Low-density polyethylene (LDPE) and also linear low-density polyethylene (LLDPE) resins can be characterized by the degree of strain hardening and down-gaging during elongation. A new method for the determination of the apparent elongational flow characteristics is presented. In a small scale apparatus, a molten monofilament is stretched under nonisothermal conditions similar to those found in tubular film extrusion. Measurement of resistance to elongational flow and apparent elongational strain rates permit the comparison of the process-ability of different resins under specified conditions. The effect of melt temperature and extension ratio are examined. The importance of the molecular structure of both LDPE and LLDPE resins on these properties is also outlined.