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R. C. Donovan 《Polymer Engineering and Science》1971,11(5):361-368
A theoretical model for the transient melting behavior in a reciprocating-screw injection molding machine is proposed. The model is based on a steady state extrusion model, Neumann's melting problem, and a heuristic postulate for the transient behavior. The model predictions are compared to experimental melting data for low density polyethylene, acrylonitrile-butadiene-styrene polymers and polyvinyl chloride for a variety of operating conditions and two screw designs. A useful degree of correlation is demonstrated for all experimental cases. 相似文献
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采用电磁动态注射成型机塑化聚丙烯(PP)与纳米CaCO_3的共混料。通过扫描电子显微镜观察以及差示扫描量热法分析,探讨了振动参数对注射机预塑过程中分散效应的影响。实验发现,随着振动频率和振幅的增加,纳米CaCO_3在PP熔体中分散得更均匀,平均粒径逐渐减小;混合料的熔点向高温移动,混合质量得以改善,有利于完善结晶。因而表明,引入振动力场有效地促进了CaCO_3的分散,提高了注塑机的塑化效果。 相似文献
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R. C. Donovan 《Polymer Engineering and Science》1974,14(2):101-111
A mathematical representation of the plasticating process in a reciprocating-screw injection-molding machine has been formulated as a design tool for simulating the effect of processing parameters on the melting performance, the melt temperature, and the pressure profile. Comparisons with experimental data on low density polyethylene (LDPE), acrylonitrile butadiene styrene (ABS), and polyvinyl chloride (PVC) under a wide variety of processing conditions are described. 相似文献
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An experimental study was conducted on the injection molding of a thermosetting polyester resin. For the study, a general-purpose unsaturated polyester resin was used, with benzoyl peroxide as initiator. A differential scanning calorimeter (DSC) was used for studying the curing kinetics, under isothermal curing conditions. A plunger-type injection-molding apparatus was constructed, and a rectangular mold cavity with glass windows on both sides was constructed, which permitted us to record on a film the changes in stress birefringence patterns in the mold cavity during the molding operation (i.e., during the isothermal cure, post cure, and subsequent cooling), using a crossed circular polariscope. The injection-molded specimens were used to determine the distribution of the degree of cure at various positions in the flow direction, and to relate the degree of cure to the dynamic mechanical properties. 相似文献
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An experimental study of two phase flow of polymer melts relating to injection molding has been carried out. The experiments specifically concern rheological phenomena which may occur when two melts are simultaneously injected through a runner system leading to a mold cavity. Injection in the form of annulus-core configurations and simple stratified flow are investigated. A new injection molding method is proposed which is based upon the latter technique. Encapsulation of one melt by the other occurs in the runner system and formation of a sandwich structure in the cavity results. Annulus-core injected configurations were only found to be stable when the lower-viscosity melt is in the annular region. 相似文献
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橡胶注射成型机注射装置结构分析研究 总被引:1,自引:0,他引:1
主要介绍了橡胶注射成型机及其注射装置的发展情况,阐述了橡胶注射成型的特点以及注射装置设计要求,并对三种常用的注射装置的结构特点及应用作系统的分析比较. 相似文献
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The present study reports on the results of an integrated experimental program to determine some of the important interactions between resin properties, moldability, and the microstructure and ultimate properties of molded articles. As part of the program, resins are characterized as to their rheological, thermal, and crystallization behavior. Then, the resins are injection molded in a laboratory machine employing simple, but highly instrumented molds in order to evaluate moldability and to produce moldings for testing and analysis. Microstructural analysis to determine morphology and orientation of the moldings is carried out utilizing polarized light microscopy and differential scanning calorimetry. Finally, shrinkage and tensile properties of the moldings are determined experimentally. To illustrate the utility of the proposed techniques, results are reported for two polyethylene resins' that exhibit superficially similar properties but, according to tests, show significant differences in moldability and product properties. 相似文献
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Sai S. Young James L. White Edward S. Clark Yasushi Oyanagi 《Polymer Engineering and Science》1980,20(12):798-804
An experimental study of sandwich injection molding is reported which involves sequential injection of polymer melts with differing melt viscosity into a mold. In isothermal injection molding the relative viscosity of the two melts is the primary variable determining the phase distribution in the mold. Generally the most uniform skin-core structure occurs when the second melt entering the mold has a slightly higher viscosity than the first melt injected. Large viscosity inequalities lead to nonuniform skin thicknesses. The influence of blowing agents and non-uniform temperature fields on the extent of encapsulation is described. Temperature fields are very important especially if the first polymer melt injected has a greater activation energy of viscous flow (or a greater temperature dependence of the viscosity function). 相似文献
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Rotational molding of foamed polyethylene has increasingly become an important process in industry because of its thicker walls, low sound transfer, high stiffness and good thermal insulation. However, the foaming process of polyethylene during rotational molding has not been well studied. The focus of this article is to assess the rotomoldability of foamed polyethylene and to investigate how blowing agents can influence the process of rotational molding and the final product quality. Rotational molding experiments were carried out in a laboratory scale uniaxial machine capable of measuring internal mold temperature in the cycle. Mechanical property tests, as well as thickness distribution and density measurements, were performed on the rotationally molded parts. Differential scanning calorimetry and optical microscopy have also been employed to identify the material and structural parameters. It was found that the presence of blowing agent results in an improvement of the impact properties, which are counteracted by longer cycle times and uneven surfaces. 相似文献
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Modeling and experimental study of birefringence in injection molding of semicrystalline polymers 总被引:2,自引:0,他引:2
The prediction of birefringence developed in injection moldings is very important in order to satisfy required specification of molded products. A novel approach for the numerical simulation of the flow-induced crystallization and frozen-in birefringence in moldings of semicrystalline polymers was proposed. The approach was based on the calculation of elastic recovery that becomes frozen when the flow-induced crystallization occurred. The flow effect on the equilibrium melting temperature elevation due to the entropy reduction between the oriented and unoriented melts was incorporated to model crystallization. To find the entropy reduction and the frozen-in elastic recovery during crystallization, a non-linear viscoelastic constitutive equation was used. From the ultimate elastic recovery the crystalline orientation function was calculated. The crystalline and amorphous contributions to the overall birefringence were obtained from the crystalline orientation function and the flow birefringence, respectively. The birefringence profiles were measured and predicted in moldings of polypropylenes of different molecular weights obtained at various melt temperatures, injection speeds, holding times and mold temperatures. The resulting predictions were in fair agreement with corresponding experimental data. 相似文献
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本文主要介绍注塑机常用的电阻式电热圈、电磁感应加热圈、纳米红外电热圈的结构及工作原理,并对三种电热圈的特性进行分析。 相似文献
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针对国内日趋激烈的注塑机市场竞争,本文主要采用科学的统计方法,对目前市场上现有的注塑机产品进行分析,找出与机器价格密切相关的机器性能参数。通过提取相关技术、财务数据,运用绘图分析的方法,充分论述了注塑机的价格与机器的合模力、注射容积、容模面积等参数都是成线性关系的。这些结论为业内企业今后如何开发新注塑机来满足客户的需要,提供了新的思路。 相似文献
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Jong-Hwei Wei Chian-Chiunn Chang Cheng-Ping Chiu 《Polymer Engineering and Science》1994,34(11):881-887
This paper presents the development of a nonlinear mathematical model and a microcomputer controlled servo-pump system for the study of the dynamics of a servo-pump controlled injection molding machine (IMM). The model is formulated by the Reynolds transport theorem which is applied to describe the polymer flow dynamics in the nozzle. The comparison between the simulation results and experimental investigations indicated that the nonlinear dynamic model is a reasonable representation of a servo-pump controlled IMM. The output flow rate and working pressure of a servo-pump controlled IMM can be reasonably represented by the nonlinear model when the acrylonitrile-butadiene-styrene (ABS) is injected. 相似文献
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An experimental and theoretical investigation of transient melt temperature during injection molding
N. Dontula P. C. Sukanek H. Devanathan G. A. Campbell 《Polymer Engineering and Science》1991,31(23):1674-1683
An in-depth study of the effect of molding parameters on melt temperature was carried out, in which the melt temperature was measured with infrared probes. The effect of screw speed, back pressure, shot size, and polymer viscosity on melt temperature during plastication was determined. The melt temperature was not constant during injection, and was found to be as much as 44°C above the barrel temperature. The temperature rise results from viscous dissipation during plastication and adiabatic compression during injection. Measured temperatures are in qualitative agreement with a first order model of the process. 相似文献
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介绍了注塑机电气控制系统的结构,具体说明了使用可编程控制器和触摸屏对注塑机传统电气控制系统进行改造的方法,分析了入机界面在该设备中的应用. 相似文献