热固性膜压料在模具中的热传导

模压料的加热过程和冷却过程是受由外而内的热量传递作用的结果，弄清模压过程的热传递，对于模压过程工艺参数合理控制是很重要的。本文就模压料在模具中加热过程和达到固化温度以后的传热过程进行定量分析，以确定合理的工艺控制参数。     

改性不饱和聚酯固化反应的研究

本文通过对环氧丙烯酸酸（ＶＥ）树脂改性不饱和聚酯（ＵＰ）树脂的固化过程的研究，制定了合理的树脂蜞体固化制度，并且求解了固化反应的动力学参数。通过对该树脂基体模压料流变性特性的研究，确定了较为合理的模压成型工艺参数。     

环氧丙烯酸酯／不饱和聚酯模压料的研制

用耐热性较高的环丙烯酸酯（ＶＥ）树脂改性不饱和聚酯树脂，得到了一种模压料的树脂基工制作了模压料，经流变性能研究，得到了合理的压制成型工艺条件。对模压制件的性能测试结果表明：其模压制品具有良好的高温力学性能和电性能，耐温指数达到１６９℃，可作为Ｆ组绝缘材料使用。     

长玻璃纤维增强聚丙烯复合材料热模压成型工艺的研究

为了提高LGFRP模压制品的基本力学性能及其性能的稳定性,把热模压成型过程细分为预热工序、模压工序和成型操作三个部分,分别对应片材加热温度、保温时间、成型压力、模具温度、保压时间、坯料转移时间以及模压排气次数七个热模压成型工艺参数,运用正交试验和单因素试验方法,分析和讨论了各工艺参数对LGFRP复合材料热模压件力学性能的影响,并优化出了较佳的工艺参数组合。结果表明,工艺参数对力学性能的影响度大小受工艺条件的影响,并且细化成型工艺可提高LGFRP热模压制品的力学性能与热模压工艺的稳定性。     

复合材料模压成型的工艺特性和影响因素分析

简述了聚合物基复合材料模压成型工艺特性,对模压成型的设备、预浸料、工装模具、工作环境条件等提出相应要求,着重对成型工艺过程中模压成型温度、压力、保温时间等工艺参数对复合材料制品性能影响做了分析,且简要介绍了复合材料模压制品可能出现的质量问题、产生原因、预防措施等内容。     

复合材料硅橡胶膨胀加压成型模具的设计与制造

硅橡胶膨胀加压成型工艺是一种改进型的复合材料加压成型方法,成型时,将硅橡胶芯模与复合材料预浸料一起放置在刚性外模内,硅橡胶加热膨胀后,对产品施加压力。因为硅橡胶的加压形式与过程调控简便,所以可以制作模压或热压罐等传统方法无法制造的产品。本文介绍了硅橡胶膨胀模设计中的压力计算和压力测量方法,并介绍硅橡胶浇注模的设计和传递式硅橡胶热膨胀模的设计。     

一种CT床面板的研制

介绍了一种CT床面板的研制,选用碳纤维预浸料做蒙皮,ROHACELL泡沫塑料做夹芯,采用模压成型工艺,通过数控加工泡沫塑料芯材,采用合理的工艺手段来控制床面板的表面和内部质量,研制出的CT床面板符合设计要求。     

玻璃钢螺栓的研制

以压制成型M10粗牙普通螺栓为例,讨论了玻璃钢螺纹的成型方法;重点介绍了适合玻璃钢螺栓模压成型的工艺、模压料的选用和使用场合;并根据螺栓的不同分型方式,设计玻璃钢螺纹的模压成型模具,确立了成型工艺条件。     

液晶玻璃窑炉冷修泄料控制

液晶玻璃窑炉普遍采用混合加热方式提供热量,电加热为主、燃气辅助加热的熔制方式,窑炉冷修泄料采用底部泄料的方式,充分的工作准备和合理的工艺控制能有效提高泄料的稳定性和安全性。本文总结实际生产经验,以提高泄料操作的效率。     

新颖的模塑工艺—无料柄注射模压成型

<正> 热固性塑料的混合模塑工艺集注射和模压工艺之所长,并补充发展了某些独特的优点,具有低耗、周期短、高效率的特点。 热固性塑料加工中准备使用的新术语是什么呢?它就是无料柄注射模压成型(RIC),可大大提高热固性塑料模制件经济效益的一种独特的模塑工艺。 它将注射模塑自动化和模压成型件质量好的优点结合起来,而且消除了注射成型和     

Optimalization of processing conditions for thermosetting polymers by determination of the degree of curing with a differential scanning calorimeter

The curing reaction of thermosetting polymers is accompanied by exothermal heat which has been measured with a differential scanning calorimeter. The Perkin-Elmer DSC-1 B was used for recording the curing behavior of a diallyl phthalate molding compound and two unsaturated polyester molding compounds. The residual heat of reaction has also been determined by a dynamic DSC scan of partly cured products made at various mold temperatures and curing times. It was thus possible to calculate the degree of curing and to dictate the optimum processing conditions for the indicated molding compounds. The interpretation of results leads to the conclusions that the DSC can be used to set specifications and to perform quality control for the molding compounds and that the most significant processing parameter is mold temperature.     

The effect of flow on cavity surface temperatures in thermoset and thermoplastic injection molding

In the Injection molding process, nonuniform heat transfer between the polymer and the mold caused by flow during the cavity filling stage can lead to spatial variations in the cavity surface temperature. This can result in an increase in cycle time or poor part quality. An investigation of the flow-induced, nonuniform, cavity surface temperature is reported here. A flow model for a thin, rectangular, end-gated cavity and a model for the steady-state temperature distribution in a simple mold are developed. These are applied to some thermosetting and thermoplastic systems. For both filled and unfilled thermosets, it is found that a simple plug flow model gives a good approximation for the heat transfer during flow. For thermoplastics, however, the full flow solution must be used. For the cases considered in this study, the steady-state temperature variation along the cavity surface is less for the thermoplastics than for the thermosets.     

注塑冷却分析模内复膜数学模型建模

由于模内复膜工艺是在模具内将塑件表面增加一层薄膜,本文利用注塑冷却分析将模具型腔表面离散为平面三角单元的特点,将薄膜和塑件视为两层具有良好接触的平板,对于每一层平板,建立第一类边界条件下一维非稳态导热模型,并将该导热模型应用到冷却分析中,完成了模内复膜冷却分析的建模.     

Modeling nonisothermal impregnation of fibrous media with reactive polymer resin

The manufacture of polymer composites through resin transfer molding (RTM) or structural reaction injection molding (SRIM) involves the impregnation of a fibrous reinforcement in a mold cavity with a reactive polymer resin. The design of RTM and SRIM operations requires an understanding of the various parameters, such as materials properties, mold geometry, and mold filling conditions, that affect the resin impregnation process. Modeling provides a potential tool for analyzing the relationships among the important parameters. The present work provides the physical model and finite element formulations for simulating the mold filling stage. Resin flow through the fibers is modeled using two-dimensional Darcian flow. Simultaneous resin reaction and heat transfer among resin, mold walls, and fibers are considered in the model. The proposed technique emphasizes the use of the least squares finite element method to solve the convection dominated mass and energy equations for the resin. Excellent numerical stability of the proposed technique provides a powerful numerical method for the modeling of polymer processing systems characterized by convection dominated transport equations. Results from example numerical studies for SRIM of polyurethane/glass fiber composites were presented to illustrate the application of the proposed model and numerical scheme.     

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.     

Enhancement of convective heat transfer to polymer manufacturing molds

Many complex and dimensionally stable plastic products are manufactured using processes such as blow molding, thermoforming, injection molding, and rotational molding due to various advantages offered by these techniques. However, in many cases, product cycle times—and hence productivity—are limited by the time required to heat up and cool down the mold and the product. This is particularly true for rotational molding of thermoplastics. Due to the complex rotation of the mold, heating and cooling are most commonly achieved by convection to the external surfaces of the mold using air as the transfer medium. The objective of this work is to achieve substantial enhancement in convective heat transfer to mold exteriors and ultimately to reduce production cycle times. In this paper, the application of extended surfaces and roughened textures to molds is investigated. Extended surfaces have the potential to enhance heat transfer by increasing the surface area. Roughness elements are utilized in conjunction with turbulent flows, also producing significant increases in heat transfer rates. A steady state analysis using well‐established techniques has been performed to estimate the heat transfer enhancement, and a series of simple experiments have been carried out. The predicted enhancements to heat transfer are substantial, and have been verified by the preliminary experimental results. POLYM. ENG. SCI. 45:114–124, 2005. © 2004 Society of Plastics Engineers     

Three-dimensional simulations of the curing step in the resin transfer molding process

The curing step in resin transfer molding process involves heat transfer coupled with the curing reaction of thermoset resin. In order to examine the curing behavior under a specified cure cycle in the resin transfer molding process, numerical simulations are carried out by three-dimensional finite elements method. An experimental study for isothermal cure kinetics of epoxy resin is conducted by using differential scanning calorimetry. Kinetic parameters based on the modified Kamal model are determined from the calorimetric data for the epoxy system, and by using these parameters, numerical simulations are performed for a hat-shaped mold. It is found from the simulation results that the temperature profile and the degree of cure are well predicted for the region inside the mold. This numerical study can provide a systematic tool in the curing process to find an optimum cure cycle and a uniform distribution of the degree of cure.     

Cavity temperature—an important parameter in the injection molding process

The paper stresses the importance of cavity temperature in the injection molding process of thermoplastics. From the study of the temperature field in the mold, it follows that there is no such thing as a uniform mold temperature. The heat balance equation for the injection mold is discussed in detail. It shows that the sum of the heat exchanges during the cycle equals zero. There is an extensive explanation of the heat transfer from the melt to the mold, the heat exchange with the environment, and between the heat exchange medium and the mold. New criteria are given for the cavity material selections. The cavity temperature is a complex function of static and dynamic parameters and should be kept constant in the equal parts of the cycle. This demands a new way of regulating the temperature.     

Reaction and thermal analysis for SMC (sheet molding compound) molding in complicated geometries

A finite element technique has been developed for coupled reaction and heat transfer analysis in which mass diffusion is negligible. The temperature unknowns are located at nodal points, while the reaction variables (species concentrations, reaction rates) are at the Gauss points in each element. With a mechanistic kinetic model, the SMC (sheet molding compound) cure in 2-D and 3-D geometries was analyzed. The results for plate-and-rib configurations show the progression of cure and heat transfer and the influence of geometry on the progression. The analysis for a flat sheet of SMC in a mold with localized heating using bubblers indicates the thermal interaction between the mold and the curing SMC. Temperature and reaction profiles are given for each case.     

滚塑工艺成型周期的数值研究

为球形中空塑料制品的滚塑工艺建立了一种新的传热理论模型,并采用Fluent软件对模具的导热、塑料层的导热和熔融、结晶相变以及内部空气的自然对流换热耦合求解。数值计算所得的模具外壁面温度和内部空气温度都与实验结果吻合较好,从而证明了理论模型的有效性。最后,采用该理论模型分别计算了在不同加热温度、加热对流换热系数以及冷却对流换热系数下的滚塑成型周期,从而确定了这些参数对成型周期的影响,并得出了增大这些参数可缩短成型周期的结论。