冷却工艺对聚乙烯管材结晶行为的影响分析

本文通过调整管材生产过程的冷却方式,控制管材内外表面冷却效果,制备具有不同结晶效果的高密度聚乙烯（HDPE）管材,并研究了不同生产工艺对HDPE管材结晶效果和环刚度、纵向回缩率的影响。本文通过改变管材冷却方式,制备不同结晶度的HDPE管材,系统分析了不同生产工艺对管材结晶度及环刚度、纵向回缩率指标的影响。通过对生产工艺的优化,最终获得高结晶度、高性能的聚乙烯管材,有利于HDPE管材在船舶给水等领域的应用推广。     

HDPE/硅钙镁晶须复合材料双壁波纹管的研制

通过研究影响管材环刚度的主要因素和提高管材环刚度的方法,确定了制备高密度聚乙烯(HDPE)／硅钙镁(SCM)晶须复合材料双壁波纹管的最佳配方;介绍了HDPE／SCM晶须复合材料双壁波纹管的制备工艺和设备．为生产高性能、低成本的塑料管材提供了新的选择。该种管材具有环刚度高、质量轻、用料省、施工安装方便和耐低温性能好等优点。     

一种矿用新型增强PE结构壁管材

基于环刚度定义(ISO 9969—2007),设计制造了一种以纤维增强高密度聚乙烯(HDPE)为原料,用于煤矿井下瓦斯抽采的新型"工字钢"缠绕结构壁管材,并对其性能进行了检测。结果表明:同传统管材相比,新型管材具有更高的环刚度以及良好的耐温性能。另外,在满足要求的条件下,同规格新型管材的单位质量显著降低,最高减幅可达44.4%。     

基于ANSYS的PE-HD实壁管性能与尺寸的关系

采用ANSYS逆向模拟分析高密度聚乙烯(PE-HD)实壁管的环刚度测试过程,研究了管材环刚度为6.3时其规格尺寸如直径和壁厚与原材料性能之间的关系,并分析了标准YD/T 841.2-2008的合理性。结果表明,材料的泊松比对管材最大变形量影响较小;材料的弯曲弹性模量越大,管材最大变形量越小;管材环刚度达到6.3时所需要的原材料弯曲弹性模量值与其径厚比成正比直线关系;标准YD/T 841.2-2008中关于某些壁厚的规定存在不合理性,即按照标准中规定的某些壁厚尺寸,生产PE-HD实壁管所用原材料无法达到环刚度为6.3时所需要的弯曲弹性模量值。     

RHDPE/MPOE/滑石粉三元共混体系力学性能的研究

针对回收高密度聚乙烯（RHDPE）制得的管材环刚度不足的缺点，采用滑石粉和自制的改性POE（MPOE）对RHDPE进行了改性，研究了滑石粉和MPOE用量对共混体系力学性能的影响。结果表明，当RHDPE／MPOE／滑石粉的质量配比为50／10／40时，体系的综合力学性能最好。自制改性剂MPOE不仅能增加RHDPE和滑石粉之间的相容性，而且对共混物具有增韧作用。RHDPE／MPOE／滑石粉共混体系中，当滑石粉用量为40％时，制得的RHDPE管材的环刚度比非改性RHDPE管材提高54％。此外，添加少量的氧化聚乙烯蜡能明显改善RHDPE／MPOE／滑石粉共混体系的加工流动性，而对共混物的其它性能影响不大。     

管材用高密度聚乙烯管材树脂研究进展

聚乙烯管材以其优异的性能广泛应用于供水、燃气输送等领域,HDPE管材树脂是近年来的研发重点。本文综述了高密度聚乙烯管材树脂的应用领域、市场情况,详细介绍了其分子结构、性能特点以及国内外高密度聚乙烯管材树脂的研究进展。     

高模量聚丙烯双壁波纹管的制备及其应用优势研究

主要制备了与聚乙烯双壁波纹管相同结构的高模量聚丙烯双壁波纹管,分析了其质量、环刚度、冲击性能等。结果表明:与高密度聚乙烯双壁波纹管相比,高模量聚丙烯双壁波纹管的环刚度较高;在相同环刚度下单位长度质量轻,可以节省原料;在0℃时保持较高的冲击性能,在应用上具有较大的优势。     

曲率对PE管材环向拉伸强度的影响

选用环向拉伸试验的方法对高密度聚乙烯（PE-HD）管材环向拉伸的强度进行检测,主要研究拉伸试样在试验进行过程之中曲率的改变对环向拉伸强度的影响,整个试验过程采取多个平行试样进行试验,用以取得准确的试验数据来确定试验结果,并就曲率对PE-HD管材环向拉伸强度影响的变化规律进行研究探讨。结果表明,同一外径的PE-HD管材,随着环向拉伸试样在试验中曲率的减小,环向拉伸强度数值减少可达10 %。     

大口径高密度聚乙烯螺旋缠绕管的开发应用研究

大口径高密度聚乙烯螺旋缠绕管是一种新型的塑料埋地排水排污管道,具有许多优良的特性。本文根据螺旋缠绕管的用途和生产情况,介绍了高密度聚乙烯螺旋缠绕管道承受外负载的机理、管材的结构、管材的生产工艺,以及管材的测试结果。     

新型聚丙烯双壁波纹管的研发与应用

本文采用全进13高性能聚丙烯（PP）原料,制备了不同米重的新型DN200的PP双壁波纹管,研究了其米重、环刚度、冲击等性能。结果表明：所制备的PP双壁波纹管环柔性均达到标准要求,环刚度随管材米重的增加而增大,在米重为2．25kg时环刚度就可以达到8．6kN／m2。与聚乙烯（PE）双壁波纹管相比,该PP双壁波纹管的环刚度更高,在同等环刚度下的单位长度质量更轻,在米重为2．25kg时,环刚度满足SN8级的要求。在0℃时PP双壁波纹管保持了较好的冲击性能,在高度2m时的冲击试验后管材未产生裂纹、裂缝或破碎。     

PR1型聚乙烯缠绕结构壁管的环刚度计算方法研究

聚乙烯缠绕结构壁管的环刚度是其抵抗径向变形的重要性能参数,影响着其外压承载能力。以PR1型截面的埋地聚乙烯缠绕结构壁管为例,对管道轴向截面进行截面单元划分,同时,综合考虑截面发生变形、局部材料迁移等情况,建立截面单元的简化计算模型,并对截面单元关键尺寸参数进行修正。在此基础上,研究PR1型聚乙烯缠绕结构壁管环刚度的计算方法;通过实例验证了PR1型聚乙烯缠绕结构壁管的截面单元的形心、惯性矩以及环刚度计算方法的准确性,相关研究方法与结果将对聚乙烯缠绕结构壁管的设计、生产与使用以及其他复杂截面管道的环刚度计算提供一定的参考作用。     

基于有限元的内肋增强聚乙烯螺旋波纹管结构优化

为减小聚乙烯(polythene以下简称PE)的用料,同时保证环刚度基本不变,对内肋增强PE螺旋波纹管进行了结构优化。利用Solidworks和ANSYS workbench进行联合仿真,建立了内肋增强PE螺旋波纹管环刚度仿真测试的有限元模型,并通过环刚度理论计算模型对其进行了验证。将波纹管内肋截面的结构高度、圆弧半径、圆角半径和内肋角度作为设计变量,以单位长度波纹管PE的用料体积作为结构优化目标,以波纹管的环刚度作为约束条件。利用ANSYS workbench中的Design Exploration模块,求得设计变量对优化目标和约束条件的影响,及优化目标和约束条件对各设计变量的敏感度,从而得到设计变量的优化解。结构优化后的内肋增强PE波纹管,在环刚度基本保持不变的情况下,单位长度波纹管的PE用料体积减少了7.72%,能有效降低用料成本。     

Correlation of rheological and mechanical properties for blends of recycled HDPE and virgin polyolefins

This article investigates the rheological and mechanical properties for blends of recycled high‐density polyethylene (HDPE) and virgin polyolefins and attempts to correlate relative shear viscosity and relative stiffness for these blends. These virgin polyolefins comprised a wide variety of flow characteristics, from high‐flow injection molding, low‐density and linear low‐density polyethylene to very low‐flow film blowing grade high‐density polyethylene. It can be seen that there is a variety of behaviors for the relative viscosity and relative stiffness of the blends studied. Relative viscosity and relative stiffness can largely be described by linear curves. This article categorizes these parameters according to the gradient of these linear curves. The difference between the relative viscosity gradient and relative stiffness gradient is identified as a product of a variety of factors, including branching content, viscosity level, and the nature of any side units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3505–3512, 2001     

Ultrasonic measurements of the elastic stiffness constants of oriented polyethylene

High density polyethylene (Rigidex 9), a high density copolymer of polyethylene and poly(butene-1) (Rigidex 2000), and low density polyethylene (Alkathene WJG 11) were oriented by hot drawing. The crystalline texture, as determined by wide- and low-angle X-ray diffraction, was a highly oriented chain axis in the draw direction with random orientation transversely and with lamellae surfaces perpendicular to the draw direction. Elastic stiffness constants were measured by a contact-probe ultrasonic pulse technique at 2.5 MHz both before and after annealing in a temperature range which did not significantly alter the crystalline texture. Assuming orthorhombic symmetry the nine stiffness constants of Rigidex 2000 and the three longitudinal and three shear stiffness constants of Rigidex 9 were measured after drawing and after subsequent annealing. Only the longitudinal constants of Alkathene were measured, as shear waves could not be transmitted. The longitudinal stiffness in the draw direction was markedly affected by drawing and by annealing, while the crystalline texture remained substantially unchanged; by comparison the other stiffness constants showed little change. Drawn Rigidex 9 reached a tensile modulus in the draw direction of 69 GPa. The results are compared with ‘static’ and low frequency measurements reported in the literature.     

Prediction and measurement of the thermal expansion coefficient of crystalline polymers

Among the increased structural demands now being made on both unfilled and reinforced plastics is that of dimensional stability under various performance environments. Crystalline polymers are heterogeneous materials consisting of two distinct phases and, as such, can be treated as molecular versions of engineering composites. This paper first outlines the general physical model whereby a crystalline polymer is considered to be a multi-ply laminate of unidirectionally reinforced plies. The calculational format is then detailed for the prediction of the stiffness and thermal expansion coefficient of an isotropic sheet of crystalline polymer and a sample calculation is given for quenched high density polyethylene. A data base is presented for the stiffness and thermal expansion coefficient of low and high density polyethylene having quenched, slowcooled, and annealed thermal histories. Comparison between experimental and predicted results yields good agreement in all cases to better than 25 percent. Implications and limitations of the predictive technique are discussed.     

Maleated High Density Polyethylene Compatibilized High Density Polyethylene/Hydroxyapatite Composites for Biomedical Applications: Properties and Characterization

The study investigated the use of maleated high density polyethylene (mHDPE) as a compatibilizer in high density polyethylene/hydroxyapatite (HDPE/HA) composites for biomedical applications. The addition of HA increased the strength and stiffness of HDPE/HA composites while the use of mHDPE in HDPE/HA composites improved its elongation at break values. The SEM images revealed that the addition of mHDPE has induced the formation of HDPE fibrils in mHDPE/HA composites. The size of apatite layer increased with simulated body fluid (SBF) immersion time and the formation of apatite layers on the surface of composites indicates excellent biocompatibility properties.     

Strength of discontinuous reinforced composites: II. Isotropic crystalline polymers

Crystalline polymers are heterogeneous materials consisting of two distinct phases. They may therefore be treated as molecular versions of engineering composite materials. This paper summarizes the physical model which, when used in conjunction with composite theory, yields a complete calculational format for stiffness, expansion strain, and yield strength. The important input parameters to the calculation are the mechanical properties of the individual constituent phases (crystalline and amorphous), the crystallite aspect ratios, the volume fraction crystallinity, allowable failure strains for a continuous crystal system, and a measure of stress concentrations and strength reduction caused by the discontinuous nature of the actual crystalline reinforcing phase. An expression for the strength reduction factor is developed and details of the stiffness and yield strength calculations are presented for high density polyethylene (HDPE). Comparison with experiment for HDPE yields excellent agreement well within the necessary design accuracy. Agreement with experiment in the case of low density polyethylene (LDPE) is not as good, but within expectations considering the degree of theory refinement and the poorer morphological data base for LDPE.     

Rotomolded polyethylene‐agave fiber composites: Effect of fiber surface treatment on the mechanical properties

In this work, a comparison between different agave fiber surface treatments has been presented to improve the mechanical properties of rotomolded natural fiber composites (NFC). The fiber treatments were carried out with sodium hydroxide, 2‐chlorobenzaldehyde, maleic anhydride grafted polyethylene, acrylic acid, methyl methacrylate, and triethoxy vinyl silane. In particular, a simple dry‐blending technique was used to introduce agave fibers in the polymer matrix (linear medium density polyethylene). The samples were produced at 15 wt% fiber content and characterized in terms of morphology, density, hardness, and mechanical properties (tension, flexural, and impact). The results showed that surface treatments improved the homogeneity (uniform morphology) of NFC and the best mechanical improvements (77% for strength and 30% for stiffness) were obtained with maleic anhydride grafted polyethylene. POLYM. ENG. SCI., 56:856–865, 2016. © 2016 Society of Plastics Engineers     

小型中空吹塑料的研制

采用CaCO3和HDPE对LLDPE进行改性,研究了CaCO3和HDPE用量对共混体系力学性能的影响。结果表明,当m（LLDPE）∶m（HDPE）∶m（CaCO3）=55∶30∶15时,体系的综合力学性能最好。HDPE对LLDPE具有增强增韧作用,此外,添加少量的CaCO3能显著改善共混材料的力学性能,所制得的改性材料可用于生产小型中空制品。