塑料齿轮拔杆的成型工艺及质量分析

分析了塑料齿轮拔杆的成型工艺和引起拔杆收缩变形及强度低的失效原因。采用定型棒对制品进行定型,以补偿拔杆的收缩变形;通过改进浇口位置来调整玻璃纤维在制品中的取向,使拔杆受力方向与玻璃纤维方向平行,从而消除了拔杆因强度不够所引起的失效。     

汽车起动机齿轮PA66/GF33拨叉的成型工艺及质量控制研究

分析了汽车起动机齿轮PA66/GF33拨叉因收缩变形引起的尺寸误差,塑料成型时材料流动所形成的纤维取向对强度的影响,分析了制品强度低的原因.通过实验,将浇口的位置由制品中部改设在叉柄的末端,浇口改进后的玻璃纤维取向单一,基木沿着水平方向分布,使得拨叉的成型的尺寸精度和强度满足了要求.     

BMC的主要组份及其作用

<正> 一、前言 用玻璃纤维增强的低收缩不饱和聚酯块状模塑复合物(Bulk Moulding Com-pound,简称BMC),其制品主要特征如下: (1)尺寸精度和尺寸稳定性好,变形小。成型收缩率在0～0.5％之间,膨胀系数1.7～2.3×10~(-5)/℃,因此制品表面光洁平整,无翘曲; (2)刚性及机械强度高;     

玻璃纤维增强PA66制品翘曲变形的研究

针对玻璃纤维增强尼龙66（PA66／GF）注射成型制品存在的翘曲变形缺陷,运用Moldflow MPI软件对PA66／GF进行了注射成型模拟分析。结果表明,GF的取向是影响PA66／GF注射成型制品翘曲变形的主要原因;增加制品厚度或增设浇口均可有效减小制品的翘曲变形.     

谈玻璃纤维增强水泥的研究与开发

玻璃纤维增强水泥简称GRC,是一种新型的复合材料,其制品的性能充分发挥了玻璃纤维的高强度、高模量、低拉伸、耐高温、不燃烧等许多特点,克服和改善了水泥和混凝土的抗拉仲强度低、许用变形小、耐冲击性能差的缺点,使其具有很高的机械强度和良好的长期耐久性.在土木、建筑等许多领域得到广泛的应用,受到各国的重视和青睐.     

基于Moldlfow的PP薄壁制品注塑工艺计算机模拟

利用Moldflow对Taguchi法和L16(45)正交表所设计出的聚丙烯(PP)薄壁制品注塑方案进行仿真,研究发现：注射时间、保压时间、保压压力是影响PP薄壁制品翘曲变形的主要因素,并且得到最优注塑参数为：注塑机料筒温度180℃,模具温度75℃,注射时间3.0 s,保压时间3.5 s,保压压力65 MPa。另外,通过CAE模流分析软件中PP薄壁制品注塑加工的翘曲变形进行仿真发现,正交试验所获得的优化工艺的总翘曲变形量为1.417 mm,翘曲变形百分比约为3.30%。其中由于冷却引起的翘曲变形量约为0.159 mm,而由收缩和取向引起的翘曲变形分别约为1.853 mm和0.904 mm。     

基于Moldflow的PP薄壁制品注塑工艺计算机模拟

利用Moldfl ow对Taguchi法和L16(45)正交表所设计出的聚丙烯(PP)薄壁制品注塑方案进行仿真,研究发现:注射时间、保压时间、保压压力是影响PP薄壁制品翘曲变形的主要因素,并且得到最优注塑参数为:注塑机料筒温度180℃,模具温度75℃,注射时间3.0 s,保压时间3.5 s,保压压力65 MPa。另外,通过CAE模流分析软件中PP薄壁制品注塑加工的翘曲变形进行仿真发现,正交试验所获得的优化工艺的总翘曲变形量为1.417 mm,翘曲变形百分比约为3.30%。其中由于冷却引起的翘曲变形量约为0.159 mm,而由收缩和取向引起的翘曲变形分别约为1.853 mm和0.904 mm。     

BMC的组成、加工和应用

<正>一、概述低收缩不饱和聚酯玻璃纤维增强模塑料(简称BMC)是以不饱和聚酯树脂为基体,将低收缩剂、交联剂、有机过氧化物、填料、短切玻璃纤维等均匀混合而成的一种新颖的成型材料.其最明显的特征是:(1)尺寸精度和尺寸稳定性好,变形小.成形收缩率在0～0.5%之间,膨胀系数1.7～2.3×10~(-5)/℃,因此制品表面光洁平稳、无翘曲;     

DTY僵丝产生原因的探讨翁智秀

介绍了在加弹机上生产高膨松、低收缩涤纶的工艺技术,探讨了拉伸比、变形温度、定型温度和定型超喂等参数对高膨松、低收缩丝质量的影响。     

注塑聚丙烯蓄电池槽两端收缩变形缺陷与对策研究

针对注塑聚丙烯(PP)蓄电池槽脱模后两端存在严重收缩变形的情况,分别测量了室温下无定型块时及安放定型块定型后室温和50℃下蓄电池槽两端的收缩变形量。结果发现,无定型块时的蓄电池槽两端收缩变形量最大,脱模后放置一周基本稳定;安放定型块定型虽能够减小其收缩变形量,但无法完全消除该类变形;定型块定型后的蓄电池槽在50℃下的收缩变形量甚至超过无定型块时的值。分析了产生这种现象的原因,发现其与PP特性及蓄电池槽结构特点有关。在此基础上提出了改善蓄电池槽两端收缩变形的对策,即延伸蓄电池槽两端筋的宽度或在其两端侧面上增加网络筋格。经过以上2种结构改进的蓄电池槽在存放3个月后其两端基本没有发生收缩变形的情况,从而较好地解决了蓄电池槽两端收缩变形的问题,满足了蓄电池装配气密性的要求。     

水泥锶渣混凝土路用性能评价

为了分析水泥锶渣混凝土用于低交通量道路路面的可行性,采用正交方法分析了水泥用量、用水量(坍落度)、砂率、碎石级配等因素对水泥锶渣混凝土抗压强度和抗折强度的影响规律,优选出合理的材料配合比;试验对不同水泥用量的水泥锶渣混凝土的力学性能、干缩性能、温缩性能和抗冻性能进行了系统评价.结果表明:水泥锶渣混凝土强度低于普通C30混凝土,但“折压比”高,弹性模量小,具有较好的抗裂性能;于缩系数比普通混凝土低20％,温缩系数为普通混凝土的53％,具有优良的抗收缩性能;抗冻性能低于普通混凝土;水泥锶渣混凝土可用于非冰冻地区低交通量道路路面.     

Thiol-terminated hyperbranched polymer for DLP 3D printing: Performance evaluation of a low shrinkage photosensitive resin

In order to lower the volume shrinkage of the DLP 3D printing photosensitive resins during printing, a thiol-terminated hyperbranched polymer (T-HBP) was synthesized and introduced into the bisphenol A epoxy acrylate (EA) based photosensitive resin system. The obtained T-HBP was characterized by FTIR and ¹H NMR spectra, and the grafting rate of sulfhydryl was determined. The mechanical properties of the photosensitive resins were measured by tensile and impact strength measurement. The glass transition temperature of the photosensitive resins was analyzed by DSC and the impact fracture surface was observed by SEM. T-HBP exhibited a much lower viscosity than its linear counterparts, and the addition of thiol improved the curing speed of the photosensitive resins. When the amount of T-HBP added was 20 wt%, the shrinkage of the photosensitive resins was reduced by about 45.5% and the impact strength increased by 33.9% compared with the control. The macromolecular spherical structure of T-HBP effectively reduced the functional group density of the photosensitive resins. In addition, the thiol-acrylate photopolymerization introduced by T-HBP further reduced the volume shrinkage of the photosensitive resins.     

水泥基体参数对水泥砂浆干缩性能的影响

采用干缩实验研究水灰比、灰砂比、水泥细度等水泥基体参数对水泥浆干缩性能的影响。结果表明,水灰比在0.35～0.60时,砂浆的干缩率随水灰比增大而增大;其它条件不变时,砂浆的干缩率随胶砂比增大而明显增大,随水泥细度提高而增大;高标号水泥的干缩率大于低标号水泥,水泥标号相同时,P.II>P.F>P.S;矿渣微粉比粉煤灰更适用于生产高性能水泥和高性能混凝土;减缩剂能明显减小水泥砂浆的干缩率。     

Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites

The tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer–filler interaction was studied using the Lorenz–Park and Kraus equations.     

Physical properties of water‐blown rigid polyurethane foams containing epoxidized soybean oil in different isocyanate indices

To explore the potential of isocyanate usage reduction, water‐blown rigid polyurethane foams were made by replacing 0, 20, and 50% of Voranoll® 490 in the B‐side of the foam formulation by epoxidized soybean oil (ESBO) with an isocyanate index ranging from 50 to 110. The compressive strength, density, and thermal conductivity of foams were measured. The foam surface temperature was monitored before and throughout the foaming reaction as an indirect indication of the foaming temperature. Increasing ESBO replacement and/or decreasing isocyanate index decreased the foam's compressive strength. The density of the foam decreased while decreasing the isocyanate index to 60. Further decrease in isocyanate index resulted in foam shrinkage causing a sharp increase in the foam density. The thermal conductivity of foams increased while decreasing the isocyanate index and increasing the ESBO replacement. Mathematical models for predicting rigid polyurethane foam density, compressive strength, and thermal conductivity were established and validated. Similar to compressive strength, the foaming temperature decreased while decreasing the isocyanate index and increasing the ESBO replacement. Because of the lower reactivity of ESBO with isocyanate, the rate of foaming temperature decrease with decreasing isocyanate index was in the order of 0% > 20% > 50% ESBO replacement. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

矿物掺和料与再生骨料对水泥强度和收缩性能的影响

矿物掺和料与再生骨料应用于水泥制品中是废弃物资源化利用的重要途径。为了研究矿物掺和料与再生骨料对水泥强度和收缩性能的影响,设计不同掺和料掺合比例与再生骨料取代率,进行不同龄期的强度、干燥收缩和早期自收缩测试。结果表明,粉煤灰降低水泥强度,而矿粉可提高水泥后期强度;粉煤灰和矿粉对水泥的干燥收缩有抑制作用,但对水泥早期自收缩有促进作用;再生骨料能够提高水泥强度,而对水泥的收缩性能无明显影响。     

Effect of surface modifications of leather on its joint strength with polyvinyl chloride

The treatment of bovine leathers with wetting and lyotropic agents followed by heating produced a strengthening of the leathers which increased their joint strength properties to polyvinyl chloride (PVC). A cohesive failure of leather was always obtained. The highest cohesive strength (or point peel strength) was obtained when the treatment was carried out at 140°C with the surfactant NFOE (8.5) (nonylphenol polyoxyethylene with 8.5 mol of oxyethylene). The lyotropic agents (CaCl₂, urea) gave very high values (a five-fold increase), whereas the water-dimethyl ketone blends and pure water resulted in a smaller improvement in cohesive strength (a three-fold increase). The improved cohesive strength of leather was mainly due to the destruction of the ordered structure of collagen fibres and to the creation of a complex entanglement network among the collagen fibres. The treatments applied to a bovine leather produced a shrinkage of 65%; the degree of shrinkage was not a function of the kind of treatment, but of the structure of the leather. The application of surface treatments to leather prior to its bonding to other substrates may mean that the roughening process of the leather, a tedious and difficult operation which is necessary in order to obtain adequate adhesive joints, can be avoided.     

轻质骨料对泡沫混凝土性能的影响及其内养护机制

为降低泡沫混凝土干燥收缩,采用轻质骨料(页岩陶粒及粉煤灰陶粒)制备泡沫混凝土,研究了轻质骨料对泡沫混凝土抗压强度、干燥收缩、内部湿度及孔结构等的影响,并分析了轻质骨料的内养护机制。结果表明,轻质骨料能够调节泡沫混凝土的内部湿度,约束基体的变形,降低泡沫混凝土的干燥收缩。而轻质骨料也会在泡沫混凝土中引入缺陷,导致其强度降低。轻质骨料中大于100 nm的墨水瓶孔是内养护效果的控制因素,大于100 nm的墨水瓶孔数量越多,轻质骨料释水能力越强,内养护效果越好,制备的泡沫混凝土干燥收缩越小。     

Effect of cement types in accelerated compressive strength testing of concrete

Four types of cements, including a shrinkage compensating cement, were used in an investigation to determine their influence on the accelerated compressive strength and modified cube strength. It was concluded that a 24-hour modified boiling water method can be used for estimating the normal 28-day cylinder compressive strength and modified cube strength with a high degree of correlation. It is shown that the type of cement must be considered in order to obtain a higher correlation coefficient and a lower error of estimate. The effect of the w/c ratio on the accelerated strength is also discussed.     

酯化淀粉原位凝固成型Al2O3陶瓷的研究

研究了以淀粉作凝胶剂原位凝固成型Al2O3陶瓷的新方法.当淀粉大分子在水溶液中加热到一定温度时,淀粉颗粒吸水溶胀,陶瓷浆料脱水并固化成坚硬的坯体;而且溶胀后的淀粉可作为粘结剂,有助于坯体固化并增加其强度.详细探讨了酯化淀粉添加量不同时,对陶瓷浆料流变特性的影响,以及对成型出素坯的线收缩、相对密度、干坯强度以及显微结构的影响.