焊接缺陷对聚乙烯管道焊接接头强度的影响

聚乙烯燃气管道由于其耐腐蚀、柔性好、施工效率高等优良特性,已逐渐在城镇燃气运输中取代钢制管道,成为主要的输送方式。聚乙烯管道的安装主要采用电熔和热熔焊接方式,存在的主要焊接缺陷有过焊、冷焊、氧化皮未去除、电阻丝错位、孔洞等,文中研究了不同焊接缺陷对聚乙烯焊接接头强度的影响程度及影响机理。采用拉伸、压扁、SEM和EDS测试方法对带有人为缺陷的焊接接头进行分析测试。拉伸、压扁力学性能结果表明,影响聚乙烯管道焊接接头强度的主要缺陷为冷焊、过焊、氧化皮未去除、电阻丝错位,其中氧化皮未去除对接头强度的影响最大,为正常焊接断裂应力的0.4%;SEM和EDS测试结果表明,含有氧化皮的管材分子链易交联、断链,流动性差,热氧老化的硬质斑块和机械划伤阻碍了聚乙烯母材大分子链的扩散,同时在紫外线、光、热等作用下,氧与聚乙烯表面分子链发生反应,形成大量羟基自由基团,使得聚乙烯分子链发生热氧老化和降解,大大降低了聚乙烯接头强度。     

Formability of AA5052/polyethylene/AA5052 sandwich sheets

The formability of AA5052/polyethylene/AA5052 sandwich sheets was experimentally studied. Three kinds of AA5052/polyethylene/AA5052 sandwich specimens with different thicknesses of core materials were prepared by the hot pressing adhesive method. Then, the uniaxial tensile tests were conducted to investigate the mechanical properties of AA5052/polyethylene/ AA5052 sandwich sheets, and the stretching tests were carried out to investigate the influences of polymer core thickness on the limit dome height of the sandwich sheet. The forming limit curves for three kinds of sandwich sheets were obtained. The experimental results show that the forming limit of the AA5052/polyethylene/AA5052 sandwich sheet is higher than that of the monolithic AA5052 sheet, and it increases with increasing the thickness of polyethylene core.     

油田三元介质对钢骨架塑料复合管性能的影响

利用浸泡试验方法结合实际应用情况,研究油田三元介质对聚乙烯材料以及钢骨架聚乙烯塑料复合管材性能的影响。研究结果表明,钢骨架塑料复合管对油田三元介质具有良好的耐腐蚀性,可以应用于油田三元介质的输送。     

Effect of plasma electrolytic oxidation coating on joining metal to plastic

Abstract

Joining of magnesium alloy to polyethylene without adhesive using a newly developed friction lap welding technology was investigated. The polyethylene and magnesium alloy were hard to be joined together without surface premodification due to the lack of polar groups on polyethylene surfaces. Strong hybrid joints were achieved after the polyethylene was treated by corona discharge, and the magnesium alloy was subjected to plasma electrolytic oxidation treatment. Scanning electron microscope and high resolution transmission electron microscope observations demonstrated that the high joining strength was attributed to the development of both chemical bonds at the interface and micromechanical interlocking.     

Effect of ambient humidity to wetting angles of various hydrophilic surfaces

The effect of ambient humidity to water and dimethyl sulfoxide wetting angles of paraffin and polyethylene terephthalate surfaces was studied. Symbasis of this relationship was found for hydrophilic polyethylene terephthalate film surface, evidencing apparently lower polarity of polyethylene terephthalate surface at higher ambient humidity. An opposite relationship of wetting angles vs. ambient humidity was observed for paraffin/water system. No relationship of wetting angles vs. ambient humidity was detected for paraffin/dimethyl sulfoxide system.     

聚乙烯亚胺对置换镀金过程中镍基体腐蚀的影响

通过)XRF、SEM、XPS、开路电位、极化曲线、电化学阻抗谱及红外漫反射等方法,分析了聚乙烯亚胺对置换镀金过程中镍基体腐蚀的影响原因.结果表明:聚乙烯亚胺降低了置换镀金初始时沉积速率,而对长时间施镀镀速的影响较小;聚乙烯亚胺降低了金层Ni、O元素的含量;该添加剂能够在镍、金表面吸附,而且优先在金表面吸附,并加速了镍表面氧化物的溶解速率.聚乙烯亚胺使化学镀镍层表面活性趋于一致,减轻了镍基体的过度腐蚀现象.     

三层聚乙烯外涂敷作业线生产速度的确定因素

介绍了三层聚乙烯外涂敷所用涂料的性能和工艺；分析了三层聚乙烯外涂敷作业线生产速度的确定因素。     

Effect of barrier discharge on stability of electret state of high-density polyethylene

The electret state of high-density polyethylene subjected to an electric gas barrier of an AC discharge is studied. It is established that under the effect of the discharge a negative charge is formed on the film surface. Using thermally stimulated polarization, we study the space-charge processes in both the thermoand corono-electrets processed in the barrier discharge in the air gap between the dielectrics (glass–polyethylene). A comparison of the stability of the electret state in polyethylene films is carried out.     

Mechanical deterioration of polyethylene greenhouses covering under arid conditions

One of the most common greenhouse covering materials in Saudi Arabia is polyethylene film. However, polyethylene films are susceptible to mechanical failure due to harsh conditions of high temperature, solar radiation, and wind as occurs in Riyadh, Saudi Arabia. This study examined effects of ambient conditions on the deterioration of mechanical properties of polyethylene films over 14 months, using an experimentally cooled empty greenhouse (3.6 m length, 2.4 m width, and 3.6 m height) covered with a single layer of 200-μm thick polyethylene.Three mechanical tests were conducted on the polyethylene samples: penetration, shear, and tension utilizing a SMS texture analyzer. The force–distance curves produced were characterized by two stages, the elastic and plastic regions. Mechanical properties were determined, including modulus of elasticity, rupture point, and total work for each stage of the three tests. Generally, mechanical resistance of the samples decreased with increased exposure time. The results of the tension tests were preferable to penetration and shear tests. For tension tests, work decreased from 21,693 N mm for new samples, to 6658 N mm after 14 months. Based on elongation at break data, the shelf life of polyethylene covers was 12 months under the tested environmental conditions. This illustrates the effect of arid conditions and age on the mechanical deterioration of polyethylene films. The presented data can be utilized to predict the deformation and mechanical behavior of greenhouse polyethylene covers at different exposure times under arid conditions.     

Changes in the mechanical characteristics of polyethylene under the effect of an electric discharge in water

Changes in the mechanical characteristics of high-pressure polyethylene used as a high-voltage insulator exposed to the action of a shock wave generated by an electric discharge in water are studied in terms of the static and dynamic properties of polyethylene and its rheological characteristics. It is shown that the dynamic characteristics of polyethylene significantly differ from its static properties and that these features must be taken into account in selecting high-voltage insulators exposed to the action of shock waves generated by an electric discharge in water.     

Effect of polyethylene glycol on electrochemically deposited trivalent chromium layers

The structural characteristics of the trivalent chromium deposits and their interfacial behavior in the plating solution with and without polyethylene glycol molecules were observed by using various electrochemical methods such as cyclic voltammetry, open circuit potential transition, electrochemical impedance spectroscopy, scanning electron microscopy and X-ray photoelectron spectrometry. It is shown that the polyethylene glycol molecules make the reductive current density lower in the trivalent chromium plating system and promote a hydrogen evolution reaction through their adsorption on the electrode surface. And the trivalent chromium layer formed from the polyethylene glycol-containing solution has somewhat higher density of cracks on its surface and results in a lower film resistance, lower polarization resistance, and higher capacitance in a corrosive atmosphere. It is also revealed that the formation of chromium carbide layer is facilitated in the presence of polyethylene glycol, which means easier electrochemical codeposition of chromium and carbon, not single chromium deposition.     

Melting and Crystallization of High- and Low-Density Polyethylenes in Mixtures with Some Oxides and Ionic Crystals after Intensive Plastic Deformation

Protection of Metals and Physical Chemistry of Surfaces - Mixtures of high-density polyethylene and low-density polyethylene with 90 wt % adamantane, cyanuric acid, BeO, SiO2, KF, AgI, and AgNO3...     

氟化条件对聚乙烯材料表面氟化层的影响

在不同氟化温度和时间的条件下,对聚乙烯材料表面进行氟化,采用扫描电镜和X射线能谱仪对表面氟化层的厚度、均匀性及表面氟含量进行了分析。结果表明:聚乙烯材料氟化层越厚,表面越不均匀,表面平滑性越差;随着温度的提高和时间的延长,氟化层表面氟含量增加,但温度提高时,氟含量增加很少,这与氟化层增厚抑制氟化反应有关。     

聚乙烯工程材料氟化层表面形貌及耐油性研究

为了研究聚乙烯工程材料氟化后的表面形貌及耐油性,采用SEM和XPS对经不同氟化浓度氟化的聚乙烯工程材料表面的形貌和元素含量进行了分析,指出在进行氟化反应时不要过度追求氟化层的厚度,而忽略了氟化层表面的均匀程度。另外,耐油性质量损失实验表明,表面氟含量高的聚乙烯工程材料具有较好的耐油性。     

马来海松酸聚乙二醇酯的制备及助焊性能

以马来海松酸酐及聚乙二醇200为原料,ZnO为催化剂,制备得到4种不同酸值的马来海松酸聚乙二醇酯,通过傅里叶红外光谱(FT-IR)对产物的结构进行表征,并考察其对Sn0.7Cu无铅钎料的助焊性能. 结果表明,当马来海松酸酐与聚乙二醇的摩尔量之比为1:0.5,1:1.0,1:1.5及1:2.0时,反应体系的酸值分别在3,4,7和10 h后达到稳定,得到的马来海松酸聚乙二醇酯的酸值分别为212.5,178,125.3,72.7 mg/g;酸值为178 mg/g的马来海松酸聚乙二醇酯对Sn0.7Cu钎料的助焊效果最佳,其在铜基板上形成的焊点饱满,表面光亮,扩展率达到75.8%,优于未经改性的天然松香.     

不同热塑性蜡基粘接剂对316L注射成型件性能的影响

用金属注射成型方法研究三种热塑性蜡基粘接剂(高密度聚乙烯、高密度聚乙烯/聚丙烯、聚丙烯)对316L不锈钢尺寸稳定性及其机械性能的影响,对三种热塑性蜡基粘接剂溶剂脱脂过程进行了分析。实验结果表明用高密度聚乙烯/聚丙烯热塑性蜡基粘接剂得到的316L不锈钢注射成型件尺寸稳定性及机械性能较好,溶剂脱脂时间较短、效果较好,其长、宽、高三维尺寸稳定性比聚丙烯热塑性蜡基粘接剂得到的注射成型件分别高46 %,40 %,20 %,密度、硬度和拉伸强度分别为7.28 g/cm₃、72.3 HRB和579MPa。     

Electrothermopolarization influence upon the structure and properties of a composition on the basis of polyethylene and Co(AlO<Subscript>2</Subscript>)<Subscript>2</Subscript>

The influence of electrothermopolarization on the structure and properties (electret, strength) of a composition on the basis of polyethylene and a low-molecular dye Co(AlO₂)₂ was investigated. It was experimentally established that the additive Co(AlO₂)₂ changes the polyethylene structure. As a result, the electret properties of the composition change. Correlation of the strength properties with the changes of the degree of the crystallinity of the polyethylene was observed.     

Numerical Simulations of the High-Velocity Impact of a Single Polymer Particle During Cold-Spray Deposition

In this paper, deposition of polymer powders was studied numerically for the cold-spray deposition technique. In cold spray, a solid particle is impacted on a substrate at high velocity. The deformation and heating upon impact have been shown to be enough to result in particle deposition and adhesion even without melting the particle. Here, a systematic analysis of a single high-density polyethylene particle impacting a semi-infinite high-density polyethylene substrate was carried out for initial velocities ranging between 150 and 250 m/s using the finite element analysis software ABAQUS Explicit. A series of numerical simulations were performed to study the effect of a number of key parameters on the particle impact dynamics. These key parameters include particle impact velocity, particle temperature, particle diameter, composition of the polyethylene particle, surface composition and the thickness of a polyethylene film on a hard metal substrate. The effect of these parameter variations on the particle impact dynamics were quantified by tracking the particle temperature, deformation, plastic strain and rebound kinetic energy. The trends observed through variation of these parameters provided physical insight into the experimentally observed window of deposition where cold-sprayed particles are mostly likely to adhere to a substrate.     

The effect of gamma irradiation on electret properties of polyethylene

The paper describes the electret properties of low-density polyethylene and the effect of gamma irradiation on them. It is shown that the thicker polyethylene film the more stable the surface potential, electric field strength, and effective surface charge density values. The negative impact of gamma-radiation on the electret properties of the films that is caused by the release of the injected charge carriers from the traps due to clearing the energy barrier thanks to radiation energy is revealed. Irradiated polyethylene films, in turn, are polarized badly in a corona discharge because of the oxygen-containing groups on the surface formed during gamma-irradiation that act as charge carrier traps with low capture energy. It was found that the formation of cross bonds in the bulk of the polymer and carbonyl groups on its surface slightly raises the degree of crystallinity and the specific volume resistivity and decreases the specific surface resistivity.     

微机控制的聚乙烯管道电熔焊机设计

电熔焊接作为一种有效的焊接方法，在聚乙烯压力管道系统中得到了广泛的应用，根据电熔焊机的设计要求，初步设计了用80196单片机控制的电熔焊机。通过对此次设计的研究。用利于进一步提高电熔焊机的自动化，对我国的聚乙烯压力管道的焊接技术有着重要的实践意义。