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Mold Temperature (mold + temperature)
Selected AbstractsA New Way to Improve Glass-Forming Ability by Controlling the Preparation Conditions of Bulk Metallic GlassADVANCED ENGINEERING MATERIALS, Issue 3 2010Jie Mao Abstract The effects of mold preheating temperature on the glass-forming ability of Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8 alloys are investigated using traditional copper mold casting. It is found that there exists an optimum mold temperature for glass-forming alloy systems. For the two Zr-based alloy systems studied the optimum mold temperature is 353,K. This is explained from the perspectives of heat transfer efficiency and the wettability between liquid alloy and copper mold. [source] Systematic optimization for the evaluation of the microinjection molding parameters of light guide plate with TOPSIS-based Taguchi methodADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010Te-Li Su Abstract A back light module is a key product for providing sufficient light source for a liquid crystal display (LCD). The light guide plate (LGP), used to increase the light usage rate, is a key component in the back light module. This study researches the microinjection molding process parameters and the quality performance of the LGP. Its purpose was to develop a combining Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) with the Taguchi method. This is to optimize the multiquality performance of the LGP for the injection molding manufacturing process, in which both the LCD and the LGP spontaneously produce the best quality performance for V-cut depth and angle. First, an L18 orthogonal array was planned for the manufacturing parameters that affect the microinjection molding process. These included cooling time, mold temperature, melt temperature, injection speed, injection pressure, packing pressure, packing switching, and packing time. The TOPSIS was used to deal with the single-quality optimization disadvantage of the Taguchi method. Then, the TOPSIS response table was used to obtain the optimized manufacturing parameters combination for a multiresponse process optimization. From the analysis of variance, the significant factors for the quality performance of the LGP could be obtained. In other words, by controlling these factors, it was possible to efficiently control the quality performance of the LGP. Finally, with the five verified experiments, the optimized processing parameters came within a 95% confidence interval. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:54,63, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20181 [source] A novel process for continuous thermal embossing of large-area nanopatterns onto polymer filmsADVANCES IN POLYMER TECHNOLOGY, Issue 4 2009Matthew D. Fagan Abstract Hot embossing and nanoimprinting processes are being widely practiced in industry. Fast and reliable production of micro/nanofeatured patterns on large-area polymer films is of a great importance. In this study, a novel roll-to-roll thermal imprinting process was developed, capable of providing a mold-heating rate of 125°C/s with sufficient temperature control to produce large-area patterns continuously at a rapid production rate. With this new process, selected micro/nano patterns were produced on a polyethylene terephthalate film at a production rate exceeding 1 m/min. The roller mold temperature played a profound role in affecting the replication quality. To achieve good feature transfer properties, an elevated roller mold temperature approaching the melting temperature of the polymer was found to be critical. Microcavity filling time calculation further revealed that the elevated roller mold temperature is also necessary for achieving a rapid film feed rate as desired in the continuous roll-to-roll process. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 28:246,256, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20167 [source] Rotational molding of two-layered polyethylene foamsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2001Shih-Jung Liu Rotational molding of polyethylene foams has increasingly become an important process in industry because of its resultant thicker walls, low sound transfer, high stiffness, and good thermal insulation. This report assesses the rotomoldability of two-layer polyethylene foamed parts. The polymeric material used in this study was linear low-density polyethylene and the foaming material was an endothemic chemical blowing agent. Two different molding methods, by powder and by pellet, were used to mold the multilayer foamed parts. Rotational molding experiments were carried out in a laboratory scale uniaxial machine, capable of measuring internal mold temperature in the cycle. Characterization of molded part properties was performed after molding. Optical microscopy was also employed to determine the bubble distribution in foamed parts. The final goal of this study was to investigate how the blowing agent and processing conditions can influence the process of rotational molding and the final product quality. It was found that the rotational molding of two-layer polyethylene foams produced parts of better impact properties, as well as fine outside surfaces. In addition, rotational molding of foamed parts by pellets saves the cost of powder grinding, but is counteracted by uneven inner surfaces. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 108,115, 2001 [source] Hierarchy crystallization structure of a polypropylene random copolymer injection-molded bar induced by a nucleating agentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Yong Wang Abstract In this work, the effect of a nucleating agent on the crystallization structure of an injection-molded bar of a polypropylene random copolymer (PPR) with sorbitol derivatives [1,2,3,4-dibenzylidene sorbitol (DBS)] has been studied. The results show that pure PPR forms a simple skin,core crystallization structure. However, PPR/DBS forms an interesting and complicated hierarchy crystallization structure: there is a transition layer between the skin layer and the core zone. In this transition layer, the crystallization structure consists of some perfect spherulites and many tiny crystallites. Further research suggests that the formation of the hierarchy crystallization structure depends on not only the content of the nucleating agent in the PPR matrix but also the mold temperature during the injection-molding processing. The crystallization behavior of PPR/DBS during the cooling process has been characterized with polarization optical microscopy and differential scanning calorimetry. The results suggest that there are different mechanisms in the crystallization process of PPR/DBS. The formation of a three-dimensional DBS network under a certain condition might be the main reason for the complicated hierarchy crystallization structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Rapid replication of nanostructures made with a polymer using simple injection moldingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008C. K. Huang Abstract It is possible to fabricate nanostructures of 25.5 nm by replication using injection molding. In this study, a silicon calibration grating was used as a mold insert to replicate high-quality nanostructures with a simple custom-made injection machine. The replicated grating with 25.5-nm nanofeatures made with a polymer was of high quality when a high mold temperature was employed and the mold was evacuated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Improvement of the Long-Term Performance of Impact-Modified Polycarbonate by Selected Heat TreatmentsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2009Tom A. P. Engels Abstract Next to the intended increase of the impact toughness, impact modification of polycarbonate generally results in an unwanted decrease in yield stress and time-to-failure under constant stress. It is demonstrated that this loss in strength can be fully compensated for by an annealing treatment, or by increasing the mold temperature. The influence of impact modification on the short- and long-term strengths of glassy polymers is predicted by the extension of existing models with a scaling rule based on the filler volume percentage. Introduction of this scaling rule in the evolution of yield stress during physical aging even allows for the direct prediction of yield stress on the basis of processing conditions. [source] The occurrence of surface roughness in gas assist injection molded nylon compositesPOLYMER COMPOSITES, Issue 2 2000Shih-Jung Liu Gas assist injection molding has increasingly become an important industrial process because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that limit the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composities. The materials used were 15 % and 35% glass-fiber filled nylon-6 composites. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. Two "float-shape" axisymmetric cavities were used. After molding, the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature, mold temperature, melt filling speed, short-shot size, gas pressure, and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness results mainly from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure. [source] A robust shock and noise model for the manufacturing of molded LDPE foamsPOLYMER ENGINEERING & SCIENCE, Issue 12 2008S. Chedly The article concerns the injection manufacturing process of molded foam sheets and their intrinsic shock and noise performances. The main goal is to optimize the physical performances of molded plastic foams at an early stage in their design and manufacturing. The effects of injection process parameters on the properties of molded LDPE foams are investigated. The input optimization parameters considered are: injection temperature, mold temperature, injection speed, plasticization back pressure, and screw rotation speed during the plasticization phase. The output optimization parameters considered are: density, shock absorption, and acoustic absorption. The experimental design method made use of the Taguchi table and central composition design. This allows us to identify simplified mathematical models for input/output and to detect the most influential input in the injection process. We conclude by validating the models and their robustness. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effect of mold temperature on the long-term viscoelastic behavior of polybutylene terepthalatePOLYMER ENGINEERING & SCIENCE, Issue 5 2008K. Banik The effect of mold temperature variation during injection molding on the long-term viscoelastic behavior of polybutylene terepthalate (PBT) was studied by dynamic mechanical thermal analysis (DMTA) and flexural creep tests. The time,temperature superposition (TTS) principle was applied to the experimental data and the master curves were created to predict their long-term behavior. The WLF and Arrhenius models were verified for the shift data in the investigating temperature range and the activation energies for the deformation process were calculated based on the Arrhenius equation. Further a four-element Burger model was applied to the creep results to represent the creep behavior of the PBT processed at two different mold temperatures and to better understand the deformation mechanism. Differential scanning calorimetry (DSC) and density measurements were accomplished to characterize the process-dependent microstructures. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Effects of molding conditions on transcription molding of microscale prism patterns using ultra-high-speed injection moldingPOLYMER ENGINEERING & SCIENCE, Issue 9 2006H. Yokoi In this study, we performed a series of molding tests to investigate the potential of microscale transcription of polymer by ultra-high-speed injection molding (UHSIM). During the tests, the injection speed was varied up to a maximum of 995 mm/s. Polymethyl methacrylate was molded under various injection molding conditions, including cavity vacuum pumping process, so as to replicate an electroformed nickel stamper exhibiting V-grooves with a pitch of 50 ,m. Surface configurations of molded samples were observed and measured using a laser scanning microscope. The transcription ratio (TR) is defined as the ratio of the depths of V-grooves in both the molded samples and the stamper. An excellent average TR of 0.97 was performed when molding at an injection rate of 800 cm3/s (injection speed of 995 mm/s), mold temperature of 80°C, and holding pressure of 120 MPa. In addition, the effect of vacuum on transcription molding was investigated in detail; the result proved that vacuum is an important factor in the enhancement of transcription fidelity. The strong influence of injection rate on the TR indicates the applicability of UHSIM to the field of transcription molding of polymers. POLYM. ENG. SCI. 46:1140,1146, 2006. © 2006 Society of Plastics Engineers. [source] Theoretical and experimental studies of anisotropic shrinkage in injection moldings of semicrystalline polymersPOLYMER ENGINEERING & SCIENCE, Issue 6 2006Keehae Kwon A novel approach to predict anisotropic shrinkage of semicrystalline polymers in injection moldings was proposed using flow-induced crystallization, frozen-in molecular orientation, elastic recovery, and PVT equation of state. The anisotropic thermal expansion and compressibility affected by the frozen-in orientation function and the elastic recovery that was not frozen during moldings were introduced to obtain the in-plane anisotropic shrinkages. The frozen-in orientation function was calculated from amorphous and crystalline contributions. The amorphous contribution was based on the frozen-in and intrinsic amorphous birefringence, whereas the crystalline contribution was based on the crystalline orientation function, which was determined from the elastic recovery and intrinsic crystalline birefringence. To model the elastic recovery and frozen-in stresses related to birefringence during molding process, a nonlinear viscoelastic constitutive equation was used with temperature- and crystallinity-dependent viscosity and relaxation time. Occurrence of the flow-induced crystallization was introduced through the elevation of melting temperature affected by entropy production during flow of the viscoelastic melt. Kinetics of the crystallization was modeled using Nakamura and Hoffman-Lauritzen equations with the rate constant affected by the elevated melting temperature. Numerous injection molding runs on polypropylene of various molecular weights were carried out by varying the packing time, flow rate, melt temperature, and mold temperature. The anisotropic shrinkage of the moldings was measured. Comparison of the experimental and simulated results indicated a good predictive capability of the proposed approach. POLYM. ENG. SCI., 46:712,728, 2006. © 2006 Society of Plastics Engineers [source] Compression process effects on filling density and replication properties of micro-surfaces during metal injection moldingASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2009Kenji Okubo Abstract To improve the surface replication properties and density of final metal injection molded (MIM) products, injection-compression molding was applied to metal-mold processing. Effects of the mold temperature and compression process conditions, such as the compression period, on the density, surface roughness, and geometry of green compacts and sintered products were investigated. The density of green compacts, cavity pressure inside the mold, and surface roughness were improved for longer compression periods of both pressure and volume control methods. Micro-scale replication properties for the V-grooves of green compacts revealed a complicated tendency involving the compression period and control method. The V-groove replication properties improved with increasing compression period, except for the volume control method and lower mold temperature. The sintered MIM products' final properties strongly affect the characteristics of green compacts. The injection-compression process for MIM products, e.g. metal,polymer complexes, can improve the surface replication properties and roughness of green compacts. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Effect of mold temperature on the long-term viscoelastic behavior of polybutylene terepthalatePOLYMER ENGINEERING & SCIENCE, Issue 5 2008K. Banik The effect of mold temperature variation during injection molding on the long-term viscoelastic behavior of polybutylene terepthalate (PBT) was studied by dynamic mechanical thermal analysis (DMTA) and flexural creep tests. The time,temperature superposition (TTS) principle was applied to the experimental data and the master curves were created to predict their long-term behavior. The WLF and Arrhenius models were verified for the shift data in the investigating temperature range and the activation energies for the deformation process were calculated based on the Arrhenius equation. Further a four-element Burger model was applied to the creep results to represent the creep behavior of the PBT processed at two different mold temperatures and to better understand the deformation mechanism. Differential scanning calorimetry (DSC) and density measurements were accomplished to characterize the process-dependent microstructures. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Replication of sub-micron features using amorphous thermoplasticsPOLYMER ENGINEERING & SCIENCE, Issue 7 2002Kari mönkkönen A comprehensive experimental study was carried out to replicate sub-micron features using the injection molding technique. For the experiments, five different plastic materials were selected according to their flow properties. The materials were polycarbonate (PC), styrene-butadiene block copolymer (SBS), impact modified poly(methyl methacrylate), methyl methacrylate-acrylonitrile-butadiene-styrene polymer (MABS), and cyclic olefin copolymer (COC). Nanofeatures down to 200-nm line width and with aspect ratios (aspect ratio = depth/width) of 1:1 could be replicated. In all selected materials, the greatest differences between the materials emerged when the aspect ratio increased to 2:1. The most favorable results were obtained with the use of high flow polycarbonate as the molding material. The best replication results were achieved when melt and mold temperatures were higher than normal values. [source] | |||||||||||||