聚氨酯反应注射成型充模流动研究

聚氨酯原料体系反应注射成型（ＲＩＭ）制品在汽车构件、商用机器外壳等制造方面得到越业越广泛的应用，同时ＲＩＭ制品也朝着体积大、注射速度快的方向发展。但目前在模具设计及工艺参数选择中仍采用经验或尝试的方法，耗费大量人力物力。为此，本文对长扁平板模聚氨酯反应注射成型（ＲＩＭ）充模流动过程进行了实验研究并建立了计算模型。得出的压力计算公式与实验结果进行了对比。结果表明在弃模时间ｔｆ远小于凝胶时间ｔｑｍ时充     

塑料特种成型技术

第三讲 特种注射成型 塑料注射成型技术朝反应性、复合、精密、节能、低噪音、易操作、小体积的方向发展。具体体现在以下四个注射工艺的工业化上:反应注射、复合注射、气辅注射、精密注射。一、反应注射成型 反应注射成型(RIM)起始于六十年代德国Bayer公司首创的聚氨酯加工技术。传统的热塑性塑料注射成型是固体物料在注射机内熔融为液体然后注入模内并在模内由液体     

矩形腔中反应注射充模过程的数值模拟

<正>1 引言 反应注射充模（RIM）是由聚氨酯工艺发展起来的新型塑料成型方法,它具有模腔压力和进料温度低、节能、模具设备简单和产品性能优良等众多优点,特别适于生产大型塑料制件。近年来国际上已大量开展相关过程的流动和传热的数值模拟研究,以发展此一成型工艺的CAD/CAE工作。本文拟在过去对热注射充模（TIM）过程的流动和传热数值模拟研究的基础上,参考国外近年在RIM数值模拟方面的成就,对典型的端面进料矩形腔内RIM过程进行数值模拟研究。     

螺杆轴向振动对圆盘模腔充模功率的影响

探讨注射成型过程中振动力场对圆盘模腔充模过程的影响，建立起数学模型，推导出相应的功率表达式，分析了振动频率和振幅对圆盘模腔充模功率的影响，而且通过实验验证了振动力场的引入使得圆盘模腔充模功率降低。     

Moldflow软件对轿车水箱盖注射成型模具温度的优化

用Moldflow软件优化轿车水箱盖注射成型的模具温度。结果表明：模具温度在175 ℃时，胶料充模时间短，充模结束时的体积固化率小，充模后35 s时的体积固化率大。Moldflow软件可以优化橡胶制品的注射成型工艺，缩短工艺和模具设计周期，提高生产效率和产品质量。     

气体辅助注射成型充模流动CAE技术

在对气体辅助注射成型充填过程进行流动分析的基础上，开发了气体辅助注射成型充模流动ＣＡＥ软件，并给出了典型算例进行验证。     

反应注射成型充模过程驻留时间分析

在反应注射成型实际生产过程中，如何选择工艺参数是一个一直使操作者为难的问题。本文利用反应注射成型过程中驻留时间的概念，通过对喷泉流模型进行适当的简化分析，得出在ＲＩＭ充模过程中驻留时间与模腔无量纲纵向ｘ坐标和模腔厚度ｚ坐标之间的关系，并得出最大驻留时间线１＝２ｘ３（１－ｚ２），作出充模过程驻留时间分布曲线。忽略ＲＩＭ充模过程的热传导项，无量纲温度Ｔ与反应进度Φ相同，是流体在模腔内驻留时间线的等值线。将数值计算的反应进度值、温度值与模型计算作比较，基本符合，偏差的出现是由于模型中对前流区的简化处理，恒定粘度假设以及忽略热传导作用。为避免在充模过程中出现过早凝胶现象，在反应进度达到凝胶点时驻留时间不应大于１，这一结论有助于ＲＩＭ加工过程工艺参数的选择     

PUU—RRIM制品中玻璃纤维的取向

通过扫描电子显微镜观察了聚氨酯脲（ＰＵＵ）体系增强反应注射成型（ＲＲＩＭ）制品中玻璃纤维的取向和分布规律。发现在流动横截面上,玻璃纤维非均一分布,其中规则取向区域与杂乱积区域交替存在,呈现多层分布结构,建立了充模过程流体流动方程,应用速度分布方程,对玻璃纤维多层分布结构进行了理论分析。     

模具浇注系统对PA66转子精密注射成型的影响

利用注射充模CAE软件，对精密注射成型PA66转子叶片模具浇注系统进行了优化设计，使PA66转子叶片在精密注射成型中质量分布均匀，并对优化前后两种方案的充模结束时的压力、充模结束时的温度、熔接线强度、填充情况、顶出时体积收缩率、缩痕指数、总体翘曲变形进行了比较，最后利用可视化实验对转子是否符合工作要求进行了验证。     

世界主要塑料期刊文献摘要

国际现代塑料(瑞士)Modern Plastics International4月号(1991)反应注射成型聚氨脂技术革新:再利用,自动化,节约材料(p40)介绍聚氨酯系树脂废弃物的再利用技术、模内着色涂层技术,新型多元醇和增强填充材料的开发等反应注射成型聚氨酯技术革新的背景.以微妙的方式,塑料与汽车市场结成紧密关系     

Mold-filling simulations for the injection molding of continuous fiber-reinforced polymer

Injection molding can be used to fabricate fiber-reinforced polymer composites by impregnating a continuous fabric mat preplaced in a mold cavity with a polymer resin. The mold-filling time is dependent on the flow and heat transfer behavior in the mold. A model is proposed that considers the non-Newtonian How through the porous fabric mat and the heat transfer between mold, fabric mat, and flowing fluid. The model was simulated for the mold filling of a carbon fiber mat with a pseudoplastic polymer solution. The results from the simulation provide Information for optimizing mold-filling parameters through proper selection of inlet fluid pressure, heat source temperature, and type of polymer-solvent system.     

Adiabatic reactive viscometry for polyurethane reaction injection molding

Adiabatic reactive rheometry involves the simultaneous measurement of viscosity and temperature changes during adiabatic polymerization. Using the adiabatic reactor method to relate temperature to fractional conversion results in a useful rheokinetic tool ideally suited for fastreacting reaction injection molding (RIM) systems for which the mold-filling step is nearly adiabatic. In this work, a small laboratory RIM machine is used to mix the reactants and deliver them to a constant stress rheometer retrofitted with a wide-gap Couette geometry and two thermocouples. Measurements on two polyurethane systems are reported. A simple cross-linking system is used to verify the adiabatic rheokinetic method through comparison to a known gel conversion. Subsequent measurements on a phase-separating RIM system show that increases in catalyst level, hard segment content, and initial reactant temperature result in a decreased gel time and an increased gel conversion. The viscosity rise profiles aid our understanding of the onset and development of phase separation. They are also essential for mold-filling models and establishing moldability criteria for these RIM systems.     

多方案填充内燃捣固镐外壳的流场分析

利用CAE技术建立ND-5型内燃捣固镐塑料外壳的注塑成型过程的物理和数学模型,分析注射成型过程中的流场,模拟分析了塑料件的多个注射成型填充过程,并分析各方案的充模特征,通过对比填充过程和缺陷,选取了最适合塑料件的注射成型方案。     

Stress birefringence patterns in molten polymers during the mold-filling and cooling process

An experimental study has been carried out to better understand the phenomenon of stress buildup during the mold-filling process in the injection molding operation. For the study, a rectangular mold with two glass windows was constructed, so that stress birefringence patterns of molten polymers flowing into the mold could be photographed with the aid of a polariscope. As a feeding system, a 1-in. extruder was used attached to the mold with a 2-ft length of stainless steel tubing having a relief valve. In this way, the injection pressure (and injection velocity) was carefully controlled to ensure that the glass windows would not be damaged. The development of stress birefringence patterns during the mold-filling process was recorded on a movie film. It was observed that, in isothermal operation, when flow stopped after the mold was filled, stresses relaxed immediately because of the very slow cooling of the mold by ambient air. However, it was observed that, as cooling proceeded, stresses were gradually built up again in the mold. It was possible, therefore, to determine the residual stress in the mold, which originates from the cooling process alone.     

基于注塑CAE的分级注射参数设定

分级注射能够提高聚合物熔体前沿的流动稳定性，改善制品的成型质量。利用Moldflow为CAE平台，通过模拟喷嘴压力曲线的特性与模腔结构的关系，识别出模腔的分级注射点；结合分级注射点对应的注射量与螺杆注射位置的对应关系，导出一个简化的分级注射参数求解模型，并依据熔体成型束缚条件对方案的可行性进行校核，结果表明该方法切实可行。     

ANSYS二次开发在RTM工艺注模过程数值模拟中的应用

本文利用ANSYS软件包求解压力场,以ANSYS软件环境下的参数设计语言编程,实现了有限单元/节点控制体积(FE/NCV)算法.编写了程序UCVFEM,UCVFEM可以处理矩形网格和三角形网格上的注模过程模拟问题.数值验证表明数值解和解析解有良好的一致性.数值实践表明本文的方法具有可充分利用ANSYS软件包的优点,缩短软件开发周期,便于软件维护等优点.     

Conductive PVC composites: Part 2. Processing performance

PVC-based plastics have a good record for injection-molding processability, early deficiencies having been corrected with additives. Because metallic flakes have unusual aspect ratios compared with conventional fillers, it has been necessary to determine the general effects of flake on injection molding. Specific objectives of the investigation were to verify processing latitude, set guidelines for optimum processing, determine the effects of processing on physical and electrical properties, and look for unusual effects due to filler configuration. Flow properties of the PVC composite were shown to be adequate for the majority of applications, and mold-filling ability of the PVC composite was found equal to that of flame-retarded polycarbonate and close to that of flame-retarded ABS.     

Decoupled Gating and Simulation for Injection Molding

Polymer process control is limited by a lack of observability and controllability of the state of the polymer melt. A new polymer processing system is described that utilizes multiple self-regulating valves to independently and dynamically control the melt pressure at multiple locations in a hot runner injection mold. Concurrently, multiple process simulations are executed in parallel to analyze the flow rates, given the pressure drops between the outlets of self-regulating valves and each mold cavity. The developed simulation utilizes a hybrid finite difference and finite element scheme to simultaneously solve the mass, momentum, and heat equations including juncture losses according to a Cogswell model. Numerical verification indicates that the flow rate predictions of the described simulations compare well with the results from a commercial mold-filling simulation. However, empirical validation indicates that the process simulation is qualitatively useful, but does not yet possess sufficient accuracy for quantitative process and quality control. The most significant sources of variance were the calibration of process data and the modeling of the polymer rheology.     

Boundary conditions in the modeling of injection mold-filling of thin cavities

A governing equation for injection mold-filling of thin cavities with a power-law fluid is derived. The interaction between upstream delivery channel flow and cavity flow results in a continuously changing gate condition as the total viscous dissipation of the delivery channel-cavity assembly is minimized. Depending upon the relative magnitude of pressure drops or viscous dissipation across the channel and the cavity, the boundary conditions which determine the cavity filling process will lie between the following two limiting cases: a Cauchy type gate condition such that the location of the melt front is completely determined by the upstream flow; a Cauchy type melt front condition in which the gate condition is controlled by the downstream flow. For most injection molding cases this may be manifested as equilibration of dissipation density on the melt front. Experimentally observed melt front locations from isothermal, Newtonian filling of a constant gap rectangular cavity and of a bi-gap rectangular cavity are reported and the validity of the limiting cases are tested.     

Glass bead-filled polypropylene part II: Mold-filling studies during injection molding

Five glass bead-filled polypropylene composites, which had been rheologically characterized, were used in mold-filling studies to investigate the influence of rigid beads (0 to 26 vol percent) in complex flow fields. The two basic flows studied were simple shear flow in an edge-gated, rectangular cavity and stagnation flow leading to diverging radial flow in a center-gated, rectangular cavity. Pigmented tracer elements were used to illustrate flow patterns and to distinguish the skin-core structure which is a consequence of the injection molding process. Despite the strong dependence of the rheological properties (both viscous and elastic) and physical properties (density, thermal conductivity, etc.) on bead volume fraction, the basic character of the polymer dominated the flow behavior of each composite and the flow patterns were unaffected by the beads. Injection pressures were increased with increasing bead fraction to maintain the same, constant volumetric flow rate (2.21 in.³/min) for each composite. Relative injection forces follow closely the relative viscosit trend.