可视化滚塑实验机加热及冷却系统的设计

讨论了可视化滚塑实验机的辅助加热技术,特别是远红外加热技术在滚塑成型中的应用,设计了一套适用于滚塑实验的小型远红外辅助加热器及测温仪器,并说明了使用过程中的注意事项.模具冷却采用风冷,兼顾实验装置设计要求的方便性,设计时加热器多采用拆卸方便的螺栓联结.     

滚塑成型工艺与设备其研究进展

本文简要说明滚塑成型工艺及其起源和优势，详细介绍了滚塑机械和国内外的发展状况、滚塑成型模具及相关技术，阐述了滚塑成型制品质量问题及其控制方法。关注现今国内外滚塑成型工艺的研究善和进展。本综述有助于深入了解滚塑行业。     

基于PLC的滚塑机控制系统设计

分析了滚塑机的控制过程及其控制要求,进行了包括控制方式、可靠性与安全性在内的系统设计,开发了基于可编程控制器(PLC)的控制系统。该系统安装在三种不同滚塑工艺的滚塑机上,已经投产且运行情况良好。     

滚塑成型新论

滚塑成型最大的优点之一是模具成本相对较低。由于在制造过程中不存在任伺压力,模具不需要象其它工艺要求的那样成本高、结构复杂。所用材料可以产生只有滚塑成型才有的效果,能生产出一些表观极好的制品,一种制品可以,日用一种聚合物制造,这对回收工艺是理想的。     

滚塑成型的进展

滚塑成型是用粉末塑料或液体塑料来生产中空制品。本文阐述了它的成型特点，对原料的要求以及加热、冷却方法等。并详细介绍了最近几年关于滚塑成型的一些研究。     

滚塑烘箱内空气和模具温度分布均匀性的仿真研究

本文为在进气道里装有调整叶片的滚塑烘箱建立了2 种传热模型。一种是烘箱内不包含滚塑模具的无模具模型,目的是从理论上研究烘箱内部空气温度分布的均匀性与叶片转角间的关系;另一种是考虑滚塑模具的大小及转动的有模具模型,目的是从理论上研究模具表面温度分布的均匀性与叶片转角间的关系。结果表明,基于这2种传热模型,通过FLUENT软件对滚塑工艺的加热过程进行了数值仿真,将上、下叶片均设置为水平方向可使得烘箱内部空气的温度分布最均匀,将上、下叶片的转角分别设置为0 °和20 °可使得2 m长模具的表面温度分布最均匀;另外通过该仿真研究,还得到了当上、下叶片均设置为水平方向时模具表面温度分布的均匀性随模具长度的变化规律。     

滚塑树脂的性能要求与选择

滚塑,又称旋转浇铸成型或旋转成型,是一种加工中空塑料制品的成型方法。该工艺是将热塑性塑料粉料加入双轴向旋转的模具中旋转、加热、熔融、聚结、塑化后使塑料布满模具整个型腔的表面,然后冷却固化成型。聚乙烯粉料（ＰＥ）以其良好的加工性和热稳定性在滚塑中获得了广泛应用。　　为了开拓新市场,旋转成型工业需要许多新原料,这些原料必须具有优良的表面硬度和高温稳定性,同时还要具备ＰＥ所不具的其他特性。本研究旨在对一些已商品化,但还没有大规模用于滚塑的聚合物的物理性能和加工性能进行深入探讨。１　文献综述１．１　旋转…     

滚塑工艺的思考

通过对滚塑工艺发展历程的回顾，阐明了滚塑是一种具有强大生命力的塑料制品成型工艺；论述了滚塑工艺的主要优点及重大缺陷，提出了我国发展滚塑工艺需要予以注意的若干问题。     

滚塑加工现状与发展趋势

本文简要介绍了目前国内外滚塑工业的现状与发展趋势。     

Reactive rotational molding

In order to identify the major fluid mechanical effects and catalog their domains of influence, an extensive study of flow behavior of reactive polyester resin systems in uniaxial, horizontal rotating systems has been undertaken. Four general flow phenomena are identified: cascading, where resin is withdrawn from the recirculating pool arid drains back; rimming, where resin is taken around the top of the cylinder by viscous forces; stable hydrocyst formation, where rings of fluid perpendicular to the axis of rotation are formed; and solid body rotation, where the resin on the mold wall is quite uniform and time-independent. For most flow conditions, the desired region of solid body rotation apparently can be reached only by passing through each of the other flow regimes. Experimental work on polyester resin systems is compared with theoretical studies on flow stability, hydrocyst formation, and withdrawal from quiescent pools, and suitable correlations are developed. It is noted that the current correlations for stable hydrocyst formation are invalid for polyester resins and a simpler correlation is proposed.     

Principles of rotational molding

Rotational molding is a process by which powdered or liquid plastics are converted into hollow articles. This paper is devoted to the theoretical understanding of the process of rotational molding. There are seven sections: The Art, wherein we describe the process, discuss previous attempts at understanding the process, and mention processes that are similar in principle to rotational molding. Transient Heating of Mold Surface, wherein we show that the criterion for selection of mold materials is the ratio of the thermal diffusivity to the thermal conductivity, and present the heating curve for a mold in a rotational mold machine. Melting of Plastic Powder in a Rotating System, wherein we discuss in detail those physical powder characteristics that are necessary for good flow within the mold cavity. Fluid Flow During Rotational Molding, wherein we discuss the velocity profiles within the melt film, point out that there is very little bulk polymer flow possible within the mold cavity under normal processing conditions, and consider capillary flow forces and surface wetting. Sinter-Melting, wherein we compare the Kuczynski-Neuville empirical sintering model with the Lontz viscoelastic model, conclude that the latter is correct for the sintering of materials such as ABS, and apply the Frenkel glass densification theory to the prediction of void disappearance in sinter-melt polymers. Degradation, wherein we compare our experimental tensile strengths of polystyrene, obtained at varying oven cycle times and oven set point temperatures, with values obtained from degradation models given in the literature. Laboratory Simulation of Rotational Molding, wherein we propose two series of experiments, the first series being carried out without using rotational molding equipment, and the second using rotational molding equipment with molds having relatively simple geometries.     

Bubble removal in rotational molding

Closed form solutions have been obtained for bubble dissolution in typical polymer melts encountered in rotational molding. The solutions are in excellent agreement with experimental data available in the literature. Using these solutions, it is shown that under typical rotational molding conditions the polymer melts may be almost saturated. As a result, bubble shrinkage occurs over long periods. Depending on the degree of saturation, surface tension may contribute substantially to the concentration gradient that drives bubble shrinkage. It is also shown that a pressure increase imposed on a nearly saturated polymer melt leads to a steep concentration gradient at the bubble/melt interface that can cause extremely fast bubble shrinkage. Applied to the rotational molding process, such a pressure increase can result in substantial cycle‐time shortening through elimination (or reduction) of the currently used excessive heating. A further benefit may be that additional resins, which at present cannot be used because of oxidation at sustained high‐temperatures, can become available to the rotational molding industry. Under the under‐saturated conditions created by a pressure increase, the effect of surface tension on the rate of bubble shrinkage is negligible.     

Motion control for uniaxial rotational molding

Motion control parameters of rotational molding can affect process efficiency and product quality. Different motion control schemes will lead to varied powder flow regimes exhibiting different levels of mixing and temperature uniformity. The change in nature of powder flow during a molding cycle suggests that varying the rotational speed could improve the powder mixing and temperature uniformity, therefore potentially reducing processing time and energy consumption. Experiments completed investigating powder flow under uniaxial rotation show that savings of up to 2.5% of the heating cycle time can be achieved. This validates the hypothesis that altering the rotational speed to maintain the ideal powder flow throughout the heating cycle can be utilized to reduce the time taken for all the polymer powder to adhere to the mold wall. The effect of rotational speed on wall thickness uniformity and impact strength were investigated and discussed. Results show a strong influence of rotational speed (and powder flow) on the wall thickness uniformity of the moldings with wall thickness uniformity deviations of up to 50% found (within the 2–35 RPM speed range tested).     

Crosslinking of rotational molding foams of polyethylene

Rotational molding of foamed polyethylene has increasingly become an important process in industry due to its ability to produce innovative and high added value parts with little specialist equipment required. The polyolefin foam production tends to achieve the highest possible cell size uniformity and cell size reduction. To improve the cell morphology of the PE foams, the cell coalescence and coarsening might be suppressed, which can be accomplished preserving the melt strength of the polymer during processing. With this aim, in this work two peroxides have been used to enhance the melt strength of a linear low‐density polyethylene by chemical crosslinking. The moldings have been processed at different oven residence times and they have been characterized according to their density, gel content, bubble size distribution and impact strength. Despite the lower crosslinking degree attained by the crosslinked foams, the results show an enhancement in the cell morphology of these moldings, which are able to keep their cell size distribution even with the longest processing times and consequently the processing window of these rotational molding foams is widened. POLYM. ENG. SCI., 47:1804–1812, 2007. © 2007 Society of Plastics Engineers     

一步法注射成型机

简述了注射成型法与模压成型法相比所具有的诸多优点，同时指出了传统注射成型方法所存在的问题。着重介绍了一步法注射成型技术及其设备的结构特点、工作原理及工作特性。     

橡胶注压成型机

介绍了宁波千普公司设计开发的橡胶注压成型机的合模机构、注压机构、液压传动系统、电控系统.对橡胶注压成型机所需要做的进一步发展和提高进行了简要的分析.     

新型注射成型机

该文重点介绍了一种新型注射成型机,其创新之处在于可控制温度,能除去注射筒内的滞留胶。