共查询到18条相似文献,搜索用时 125 毫秒
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顺序共注成型的实验研究 总被引:13,自引:0,他引:13
研究了顺序共注成型中几个主要工艺参数——流变性能、壳层预填充量、延迟时间对成型的影响,分析造成熔体前沿突破的原因,提出工艺设计的指导原则。 相似文献
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顺序共注射模塑中的芯层熔体前沿冲破是造成共注制品报废的重要原因之一,合理控制壳层预填充量可预防此现象发生。从运动学角度探讨芯层熔体冲破的影响因素,建立预测最小壳层预填充量的方程,并在Moldflow平台上进行验证。发现芯壳层熔体黏度比R较小时,该方程的预测值相对数值模拟结果偏大;反之亦然。 相似文献
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顺序共注成型芯层熔体前沿突破的数值模拟研究 总被引:9,自引:2,他引:9
基于Hele-Shaw流动模型,运用CAE技术,模拟了聚合物流变性能及重要工艺参数对顺序共注成型芯层熔体前沿突破过程的影响,并用流变学理论揭示其影响机理。 相似文献
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基于Hele-Shaw模型,采用CAE技术,模拟了顺序共注成型中几个重要工艺参数——温度、壳层预填充量、注射速度等对其成型过程的影响。并用流变学理论进行分析,揭示了各工艺参数对顺序共注成型的影响机理。 相似文献
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聚合物流变性能对共注射成型的影响 总被引:3,自引:0,他引:3
在共注射成型多相分层流动充模成型机理的基础上,揭示了芯壳层熔体对共注射成型的分层界面形貌和芯层熔体前沿突破的影响,并模拟了芯壳层熔体粘度比对共注射成型的影响,建立了芯壳层熔体粘度与分层界面和前沿移动界面菜貌的关系。本文的模拟研究结果与一些文献的实验结果相吻合。 相似文献
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In co-injection molding, the properties and distribution of polymers will affect the application of products. The focus of this work is to investigate the effect of molding parameters on the skin/core material distribution based on three-dimensional (3-D) flow and heat transfer model for the sequential co-injection molding process, and the flow behaviors and material distributions of skin and core melts inside a slightly complex cavity (dog-bone shaped cavity) are predicted numerically. The governing equations of fluids in mold are solved by finite volume method and Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm on collocated meshes, and the domain extension technique is employed in numerical method for this cavity to assure that the numerical algorithm is implemented successfully. The level set transport equation which is used to trace the free surfaces in co-injection molding is discretized and solved by the 5th-order Weighted Essentially Non-Oscillatory (WENO) scheme in space and 3rd-order Total Variation Diminishing Runger-Kutta (TVD-R-K) scheme in time respectively. Numerical simulations are conducted under various volume fraction of core melt, skin and core melt temperatures, skin and core melt flow rates. The predicted results of material distribution in length, width and thickness directions are in close agreement with the experimental results, which indicate that volume fraction of core melt, core melt temperature and core melt flow rate are principal factors that have a significant influence on material distribution. Numerical results demonstrate the effectiveness of the 3-D model and the corresponding numerical methods in this work, which can be used to predict the melt flow behaviors and material distribution in the process of sequential co-injection molding. 相似文献
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Kiril P. Tchomakov Basil D. Favis Michel A. Huneault Michel F. Champagne Florin Tofan 《Polymer Engineering and Science》2004,44(4):749-759
Ternary blends of PS and PMMA in a PE matrix were prepared by twin‐screw extrusion to investigate the core/shell encapsulation phenomenon in the composite droplet. The PS was found to encapsulate the PMMA to form composite droplets within the PE matrix as expected from the spreading coefficient theory. The effects of dispersed phase concentration, viscosity ratio, feeding sequence and twin‐screw operating conditions were investigated. The blend morphology was observed by scanning electron microscopy after selective extraction of either PS or PMMA, and average core and composite droplet diameters were determined by image analysis. Although it is known that the structure of composite droplet blends can be substantially altered through control of the volume fraction of the components in the dispersed phase, this study demonstrates that blends with a 1:1 composite droplet volume fraction are relatively stable to large variations in the minor phase viscosities and processing conditions. Twin‐screw extrusion thus provides a highly robust technique for the melt processing of blends possessing composite droplet morphologies. Polym. Eng. Sci. 44:749–759, 2004. © 2004 Society of Plastics Engineers. 相似文献
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通过电子显微镜观测聚丙烯/中空微珠(HGB)复合体系的微观形貌图;分析了HGB在聚合物基体中的分散状况。结果显示:随着填充物的体积分数增大及粒径的减小,复合体系中HGB的数量明显增加,出现了一定程度的团聚现象。PP/HGB流动曲线呈很好的线性,线性相关系数均大于0.99,说明熔体的黏度变化平稳,也表明HGB的分散均匀,团聚现象不严重。随着HGB的体积分数增大或粒径降低,HGB团聚现象有一定增加,使得"摩擦损耗"作用及"剪切损耗"作用增大,体系黏度也随之增大。随着HGB粒径的增大,体系流动能力增强,弱化了HGB的隔热效应,提高了熔体的温敏性,即:黏流活化能增大。 相似文献
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通过微孔发泡注射成型和传统注射成型定量对比分析,系统分析了两种成型在翘曲变形、体积收缩、残余应力、温度场分布等方面的本质区别,并基于流变学理论,揭示了微孔发泡注射成型的成型机理。结果表明,微孔发泡注射成型的翘曲变形、残余应力、成型压力和成型时间明显小于传统注射成型的,且微孔发泡注射成型的翘曲变形和残余应力随着开始发泡的熔体预填充体积分数减小而减小,微孔发泡注射成型的熔体温度在浇口附近低于传统注射成型熔体温度,而在远离浇口处则要高。 相似文献
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硅藻土含量及粒径对聚丙烯复合材料流动特性的影响 总被引:8,自引:5,他引:3
应用熔体流动速率仪测量了3种硅藻土填充聚丙烯复合材料的熔体体积流动速率(MVR),以考察填料含量和粒径对复合体系流动特性的影响。结果表明:复合材料的MVR随着温度的提高和载荷的增加而呈非线性函数形式增大;而随着填料体积分数和粒径的增加而下降。 相似文献
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采用Moldtlow公司MPI软件中的Co-injection分析模块,对夹芯注塑成型过程进行动态模拟分析,揭示矩形制品的形状及浇口位置对夹芯注塑充模过程中芯层熔体前缘冲破的影响规律。实验发现:矩形制品厚度的增加和宽度的减小可以提高前缘冲破时刻芯层熔体的体积分数(N值);制品长度对前缘冲破的影响存在一个最佳值,在小宽度情况下,长宽比增加N值也随之增加;选择高的充模流速和进料方向平行于熔体流动方向的浇口位置都会有利于芯层熔体的充模过程。 相似文献