低收缩聚丙烯的研究

用预膨胀材料与聚丙烯(PP)共混制备低收缩材料.该体系经过预膨胀材料的高温膨胀填补材料的收缩,其制品表面光滑平整,成型收缩率大幅度降低,且力学性能保持稳定.研究了预膨胀材料的加入对共混体系的力学性能、尺言稳定性的影响.研究表明:预膨胀材料的加入大幅度降低了制品的成型收缩率,同时制品的拉伸强度、弯曲强度保持稳定,一定程度上提高了制品的冲击强度.     

塑料旋转成型用PP/CMC浆液体系稳定性机理的研究

研究了以粉状聚丙烯(PP)为原料、以羧甲基纤维素(CMC)为稳定剂的旋转成型用浆液料的稳定性机理。发现在PP／CMC浆液料体系中PP颗粒的上浮过程存在着干扰上浮效应和气泡效应。干扰上浮效应有利于提高浆液的稳定性，而气泡效应则有不利影响。陈化工艺有利于消除浆液中的气泡，是提高旋转成型制品质量的一种有效方法。     

打印方式对熔融沉积成型制品性能的影响

通过挤出成型制备了可用于熔融沉积成型(FDM)的聚乳酸(PLA)/麦秸粉复合线材,然后打印成标准测试样条。研究了填充密度、层厚、打印速度、温度对3D打印制品的密度、打印时间、弯曲强度、弯曲模量、冲击强度以及动态力学性能的影响。结果表明:当打印制品的填充密度从20%提高到100%时,可以获得更高的力学性能和模量,弯曲强度、弯曲模量、冲击强度、储能模量分别提高了88.46%、44.20%、75.93%、43.39%,打印时间则延长了50.82%;当层厚从0.2 mm增加到0.7 mm时,制品的弯曲强度、弯曲模量、冲击强度分别下降了42.01%、39.94%、44.27%,但打印时间缩短了70.65%;当打印速度从20 mm/s提高到60 mm/s时,制品的弯曲强度、弯曲模量、冲击强度分别下降了33.52%、39.71%、37.14%,但打印时间缩短了43.75%;此外,温度的升高有利于制品层间的结合,当温度从190℃升至240℃时,制品的弯曲强度、弯曲模量、冲击强度分别提高了55.82%、33.33%、25.08%,但对打印时间没有影响。     

聚乙烯旋转模塑成型工艺条件的研究

本文通过正交试验的方法研究了聚乙烯旋转模塑成型工艺中主要操作参数对制品性能的影响,得到了适宜的工艺条件。结果表明在一定范围内,增加加热温度有利于改善制品的冲击性能,而工艺条件对制品的拉伸强度影响不大。     

电磁动态注塑对等规聚丙烯增韧和增强研究

利用普通注射成型和电磁动态注塑机注射成型制备等规聚丙烯试样，并对其进行拉伸强度、冲击强度、差示扫描量热仪（DSC）和广角X射线衍射（WAXD）测试。对动态与稳态注射成型聚丙烯制品的力学性能进行了比较，并结合微观测试结果，深入探讨了制品微观结构与力学性能之间的关系。力学测试结果表明，动态成型制品的拉伸性能和冲击性能比稳态加工条件下都有所提高，尤其是制品冲击性能的提高幅度可以达到40％以上，实现了对制品的同时增强和增韧。DSC和WAXD测试表明，动态成型制品的结晶比稳态制品完善，并且晶粒尺寸也小于稳态制品。经过理论分析，认为结晶情况的改善是制品拉伸强度提高的原因，而晶粒细化则大幅度提高了制品的冲击强度。     

成核剂对PP特性的改良

Milliken Chemical公司研制开发了一种PP共聚体用成核剂,它以磷酸酯盐和醋酸山梨醇酯为主要成份,它的结晶半衰期为0．78,小于millad3988(2．82),以及安息香酸钠(8．05),可以显著提高结晶化速度,缩短注射成型周期。得到的成型制品的刚性和冲击强度的平衡性良好,并具有良好的尺寸稳定性。将成型制品室温下放置48小时后几乎没有发现收缩现象。     

塑料滚塑制品缺陷分析及解决方案

简要介绍了旋转滚塑成型的方法和用途,指出了研究并解决滚塑制品缺陷的目的和意义。通过对滚塑制品较常见的几种缺陷的形成原因进行分析,从制品原材料、模具结构设计、滚塑成型工艺等方面提出了旋转滚塑成型的基本要求,同时提出了为获得高质量滚塑制品时应避免或减少各种缺陷的解决方案。     

碳纤维预浸料成型自行车结构件气泡原因及解决方案

使用UTS-50/B201预浸料通过袋压法成型工艺制作自行车车架,在固化及胶接保温处理后均产生了气泡,增加了后续劳动强度和工作时间,从而增加了生产成本,降低了生产效率。研究结果表明,通过调整树脂体系的粘性、热焓、凝胶时间以及预浸料的树脂流动度,可有效减少乃至消除制品中的气泡。     

基于极差分析的SMC复合材料模压工艺参数优化

为了探讨模压成型参数对于片状模塑料（SMC）材料模压制品综合力学性能的影响,将模压成型过程分为3个阶段,以3个阶段的压力与时间共6个参数作为影响因子,对制品的拉伸强度、弯曲强度与冲击强度进行测试,设计了正交试验,以制品的力学性能作为评价指标,采用极差分析法,分析讨论了各阶段工艺参数对SMC复合材料制品力学性能的影响,并结合成型过程中材料状态变化分析造成实验结果的原因,最终得到优化后的工艺参数。     

提高发泡树脂的性能

<正> 美国马萨诸塞州工科大学研制了一种树脂用量少,成型品强度高的发泡树脂制品的制法。传统法用化学或物理发泡剂,以及使用硅石类的核成形剂,它们不能均匀地分散在树脂中,还形成很多气泡,成型品中的晶     

旋转成型工艺条件对制品内部气泡多少影响

讨论旋转成型的工艺参数对气泡形成影响和消险办法；提出要获得高质量的制品，必须使用高ＭＦＩ的物料，并具有较小的粒度，较高的加热温度。     

预聚体法合成聚氨酯弹性体常见问题分析

对预聚体法合成浇注型聚氨酯弹性体中所出现的气泡多、粘度大、物料变黄等不良现象进行了详细的分析,从它的合成和固化成型过程中查找原因,从而提出解决方法。     

非均相孔隙纤维介质的RTM工艺探讨

分析了现有树脂的流动模型、工艺过程中气泡的形成和排出以及现有模型用于非均相孔隙纤维介质体系的差距，并讨论了材料性能、压力控制以及真空辅助手段对ＲＴＭ工艺、制件性能的影响。     

微发泡注塑制品表面质量的优化研究

以聚丙烯(PP)和高纯氮气为原料,采用高压短时和低压长时两种注气方式进行了微发泡注塑实验,并在以低压长时为注气方式的实验中,在不同熔体温度、注气压差和储料长度下,研究了冷却时间与制品表面出现大气泡概率之间的关系.结果表明,通过高压短时注气方式得到的制品表面出现大气泡的概率较高,严重影响制品质量;采用低压长时注气方式,制...     

Versuchsaufbau zur beschleunigten Bildung von Fouling aus Magermilchkonzentrat

Air bubbles on heating surfaces have a siginificant influence on fouling of protein containing products. The formation of fouling has been investigated in a pilot plant under constant conditions. Fouling layers were analyzed with respect to mass, thickness and composition. Adsorption of air bubbles on the heating surface, together with a high wall temperature difference, and a low flow velocity resulted in a considerable shortening of the induction period as well as heavy deposits of fouling. The growth of air bubbles within the fouling layer increased with experimental progression.     

PREDICTION OF VOID FRACTION AND VELOCITY PROFILES OF BUBBLY FLOWS IN VERTICAL PIPES

Adopting a similar approach to Beyerlein et al. (1985), void fraction distributions in turbulent two-phase bubbly air/water upflows and downflows in vertical pipes were analyzed using a simple transport model which was based on the assumptions that the lateral shear-induced lift force acting on bubbles (Thomas et al., 1983) is balanced by bubble dispersion, and that bubbles in the flow are conserved i.e. no bubble breakup or coalescence occurs. The model shows the importance of considering the lateral lift force experienced by bubbles as they move relative to the liquid phase in a non-uniform velocity field. This force causes the bubbles to accumulate near the wall forming a high concentration for upward flow, while the concentration increases toward the centre of the pipe for downward flow. The eddy diffusivity, as widely used in calculation of single-phase flow, can be extended to include the effect of pseudo-turbulence (Lance and Balaille, 1991) due to bubbles, and thus can be linked with the bubble dispersion coefficient. It is also demonstrated that the transverse or radial pressure gradient induced by the Reynolds stress exerts a lateral force on the bubbles, and thus affects their distribution in the flow. A comparison of the model predictions with experimental data from Serizawa et al. (1975) for upflows and Wang et al. (1987) for both upflows and downflows shows that our model predicts void fraction peaking near the wall for upflows and coring at the centre-line for downflows. Compared with similar investigations (e.g., Drew and Lahey, 1982; Lopez de Bertodano et al., 1990) of the same problem, our model approach appears to be simpler and more suitable for engineering calculations.     

Bubble Nucleation and Growth in Microcellular Injection Molding Processes

Bubble nucleation and growth are the key steps in polymer foam generation processes. The mechanical properties of foamed polymer are closely related to the size of bubbles created inside the material. Thus, it is necessary to study how to improve mechanical strength by producing extremely fine bubbles inside polymer resin. We developed a theoretical framework to help produce uniformly distributed microcellular bubbles and experimentally verified the theoretical analysis results using an injection molding machine modified to make microcellular foaming products.     

炻瓷杯表观缺陷的成因分析

本文通过断面电子扫描显微镜（ＳＥＭ），观察了炻瓷杯不同部位釉层及中间过滤层的形貌分析了表现缺陷的形成原因，表观缺陷主要表现为釉泡和氧化铁颗粒，且其集中于杯体下部外侧面，结果表明，釉泡的形成是由于在杯体下部外侧具有低的表层密度，因而，釉料的粘附量，渗入量和渗入深度均高于上部，氧化铁颗粒的引入是烧成窑内气氛的扰动造成的。     

DYNAMIC EFFECTS OF BUBBLE MOTION

The dynamic effects of the motion of single bubbles entrained in a liquid are investigated. Extensive original experimental results are presented on the pressures associated with the motion of large, isolated spherical cap air bubbles rising both freely and through constricting orifices in a vertical cylindrical pipe filled with quiescent water. The pressures, measured at the pipe wall, were found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation.     

DYNAMIC EFFECTS OF BUBBLE MOTION

The dynamic effects of the motion of single bubbles entrained in a liquid are investigated. Extensive original experimental results are presented on the pressures associated with the motion of large, isolated spherical cap air bubbles rising both freely and through constricting orifices in a vertical cylindrical pipe filled with quiescent water. The pressures, measured at the pipe wall, were found to be as high as the dynamic bubble pressure for translational bubble motion, and an order of magnitude larger for oscillatory bubble motion following bubble formation.