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Mold Surface (mold + surface)

Distribution by Scientific Domains

Polymers and Materials Science	80%

Selected Abstracts

Predicting the Mircostructure in Semi-Crystalline Thermoplastics using Software for the Simulation of Recrystallization in Metals,

ADVANCED ENGINEERING MATERIALS, Issue 3 2003
W. Michaeli
A software for the simulation of spherulite growth during the cooling of a quiescent melt has been developed and tested vs. experimental data by the authors. The tests have verified good qualitative results: the calculated crystal microstructure and distribution (see Figure for a simulated pattern close to the mold surface) correspond well with the real morphology. [source]

Visual perception and measurements of texture and gloss of injection-molded plastics

POLYMER ENGINEERING & SCIENCE, Issue 2 2009
Sofie Ignell
The effect of an imposed texture on the gloss of injection-molded polymeric surfaces was evaluated as well as the way in which these properties are visually perceived. Specimens having small differences in surface topography were produced using two mold cavities with slight differences in texture and three different polymers. The texture and gloss were characterized using laser profilometry, gloss measurements, and by means of psychometric evaluations. The measured surface topography parameters and gloss were determined mainly by the texture of the mold surface and the gloss also by the processing conditions. Variations in surface topography due to differences in the rheological properties of the polymer melts were, in most cases, too small to be reflected in the measurements. The visual assessments of the texture and the gloss of specimens from the same cavity were in fair agreement with the measurements, although the observers could discern differences between some specimens not revealed by the measurements. When the specimens molded in the two cavities differing significantly both in gloss and texture were compared, the agreement between the measured topography parameters and the perceived roughness was poorer. It is suggested that higher gloss of a textured surface enhances the perception of a higher roughness. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers [source]

Modeling of rotational molding process: Multi-layer slip-flow model, phase-change, and warpage

POLYMER ENGINEERING & SCIENCE, Issue 7 2006
K.K. Lim
A new multilayer slip-flow model has been developed to simplify and to overcome current numerical difficulties of two-dimensional model in predicting the internal air temperature inside a mold during a rotational molding process. The proposed methodology considers a macroscopic "layer-by-layer" deposition of a heating polymer bed onto the inner mold surface. A semi-implicit approach is introduced and applied to compute the complex thermal interactions between the internal air and its surroundings. In the model, the lumped-parameter system and the coincident node technique are incorporated with the Galerkin finite element model to address the internal air and the deposition of molten polymer beds, respectively. The simple phase-change algorithm has been proposed to improve the computational cost, numerical nonlinearity, and predicted results. The thermal aspects of the inherent warpage are explored to study its correlation to the weak apparent crystallization-induced plateau in the temperature profile of the internal air, as in practice. The overall predicted results are in favor with the available experimental data for rotomolded parts of cross-sectional thicknesses up to 12 mm. POLYM. ENG. SCI. 46:960,969, 2006. © 2006 Society of Plastics Engineers [source]

Effects of defrosting period on mold adhesion force of epoxy molding compound

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009
Hwe-Zhong Chen
Abstract In integrated circuit (IC) packaging, when epoxy-molding compound (EMC) is filled in the mold cavity and cured in the mold, adhesion occurs in the interface between EMC and the mold surface. Too large an adhesion force can cause many problems. For example, too large an adhesion force may damage an IC during ejection and cause the package to fail and thus lower the yield rate. To resolve mold adhesion problems, improving the mold design and applying suitable surface treatments, such as mold surface coating, are the common approaches. Applying suitable surface coating is a more popular and practical approach. Defrosting is a process to increase the frozen EMC temperature to room temperature, and to retain it at room temperature for some period before molding. It is a common practice to put EMC under required atmospheric environment during defrosting. It has been found by molding engineers that increased defrosting period will increase the frequency of mold cleaning. But there is no quantitative description on how much the adhesion force increases during the defrosting process. This paper describes the use of a semiautomatic EMC adhesion force test instrument to measure the normal adhesion force between the mold surface and EMC. By measuring the adhesion force, one can quantify how much adhesion force exists between EMC and the mold surface under different defrosting periods. The results show that it is best to use the EMC with 24,32 h of defrosting, to prevent excessive amount of mold adhesion force and it has been found that the adhesion force of the 24 h defrosting period will be 24% less than that of the 48 h defrosting period. Decreasing moisture absorption will decrease the increase in adhesion force for prolonged defrosting period cases. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Rotational molding cycle time reduction through surface enhanced molds: Part A,Theoretical study

POLYMER ENGINEERING & SCIENCE, Issue 9 2007
M.Z. Abdullah
Rotational molding has been regarded as a plastic molding method with great potential. The process offers virtually stress-free products having no weld lines or material wastage, and utilizes relatively inexpensive molds. Yet its widespread growth is hindered due to long production cycle times, which are limited by the time required to heat up and cool down the mold and the product. To address this issue, efforts have been made to enhance heat transfer to and from molds, ultimately reducing cycle times. The application of extended and rough surfaces to molds is investigated here. The aim of this study is to predict reductions in cycle time due to the enhancement of mold surfaces (i.e. roughness-enhanced and pin-enhanced molds). By utilizing a combination of heat transfer correlations, numerical analysis, and an existing rotational molding process simulation, cycle time predictions were made. The average predicted cycle time reductions were ,21 and 32% for the roughness-enhanced and pin-enhanced molds considered, under a variety of conditions. POLYM. ENG. SCI., 47:1406,1419, 2007. © 2007 Society of Plastics Engineers [source]