The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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EFFECT OF PROCESS CONDITIONS ON THE CRYSTAL STRUCTURE AND PROPERTIES OF POLYPROPYLENE CAST FILMS
Cast films of a high molecular weight linear polypropylene (L-PP) were prepared by extrusion followed by stretching using a chill roll. An air knife was employed to supply air to the film surface right at the exit of the die. The effects of air cooling conditions, chill roll temperature, and draw ratio on the row-nucleated lamellar crystallization and mechanical properties of the PP cast films were investigated. The results showed that air cooling and cast roll temperature have crucial roles on the orientation and lamellae formation as well as on the mechanical and tear properties of the cast films.
STUDY ON THE ELECTRICAL CONDUCTIVITY OF BIPOLAR PLATE WITH DIFFERENT MOLDING PROCESSES USED FOR FUEL CELL
Bipolar plates of Polyphenylene Sulphide (PPS) with 50 wt% carbon-fibers (CF) were molded by injection molding (IM) and injection-compression molding (ICM) with an assistance of induction heating (IH) and gas heating (GH) for mold temperature control. In-plane conductivity (IPC) was measured by four point probe, while through-plane resistance (TPR) was measured by the contact resistance method. Carbon fiber orientation was examined by Scanning Electrical Micrograph (SEM). ICM reduces TPR by 15% and increases IPC by 35%. TPR and IPC can be further improved by 19% and 40%, respectively, using IH whereas GH improves TPR and IPC by 23% and 91%, correspondingly. Optimum values of IPC and TPR are 155 S/cm and 1.56 ??.
DISCONTINUOUS-THICKNESS-VARIATION TO MINIMIZE WARPAGE OF PLASTICS PARTS INJECTION MOLDED UNDER UNBALANCED MOLD COOLING
Discontinuous variations of part thickness (From 10% to 40%) in a pitched manner were designed to match with various mold temperature difference between the mold core and cavity sides. Their effects on part warpage were investigated. Results show that part warpage will reach max value when there is unbalanced mold temperature of 30?øC with a 40% local thickness variation. In unbalanced cooling, the neutral axis will deviate from the gap center toward the mold wall of the higher temperature. Using variations in thickness and different mold temperatures we can control the part warpage value and location.
WEATHERING PERFORMANCE ADVANTAGES OF MOLD-IN-COLOR ACRYLIC VERSUS COATED PLASTICS FOR EXTERIOR TRIM APPLICATIONS
This paper will explore the actual outdoor weathering performance of multiple plastic technologies used for exterior trim including various approaches to coatings and the use of molded in color acrylic. For each technology, actual 5-year old parts were obtained and then photographed along side new parts to visualize change in appearance. Next the specimens are analyzed for change in color and gloss.Finally the parts are analyzed for surface chemistry changes via infrared spectroscopy. Changes in surface chemistry and appearance after weathering are associated with the chemical nature of each polymer. While the weatherable mold-in-color PMMA does not change, it is concluded that many of the coating technologies used to protect plastics that are not weatherable deteriorate after 5 years of outdoor usage and that degradation of the plastic still occurs.
ABS+PA INNOVATION FOR AUTOMOTIVE INTERIORS
The need for automotive interior molded-in-color (MIC) low gloss, rigid plastic components with good scratch and mar resistance is well known. Typical interior product gloss targets of automotive Original Equipment Manufacturers (OEMs) now range from 1.5 - 2.5 units for sixty degree Gardner gloss. Interior scratch objectives require a scratch width of less then four tenths of a millimeter with slight whitening when a 15 Newton load is applied via a one millimeter hemispherical tip.Strength and rigidity requirements now range from 1.0mm to 3.0mm max deflection on high touch interior areas when subjected to an arm or finger loading.Recent advancements in the field of Acrylonitrile- Butadiene-Styrene + Polyamide (ABS+PA) blends by BASF Corporation have allowed for such a copolymer that with the proper design and tooling considerations allows one to meet these specifications.
USING PULSED COOLING TO REDUCE CYCLE TIME AND IMPROVE PART WARPAGE
Pulsed cooling enables proper high mold temperature within a given molding period and is a convenient way to carry out dynamic mold temperature control. In this study, we compare the effects of the cooling efficiency of conventional cooling and pulsed cooling under different conditions of mold temperature, coolant temperature, melt temperature, and flow rate. It was found that pulsed cooling can improve cooling efficiency from 0.288?øC/s to 0.631?øC/s, compared to conventional cooling, and improve warpage by 20% as well. To reach the same level of warpage as that of conventional cooling, cooling time for pulsed cooling can be reduced roughly 30%.
FAILURE ANALYSIS AND DESIGN MODIFICATIONS OF A CHILD CARRYING BOARD
The paper is about a board that is coupled behind a baby's carriage to transport kids up till 4 years old. The kid seats on an L-shaped bench of which one leg is fastened to the board by snap-fit assemblies. Static tests and initial tests at T??V on boards from trial production in China did not show failures and production was started. Further field tests showed, however, early crack initiation and propagation. The material selection and ribbing needed to be improved. The paper will demonstrate that by selecting appropriate semi-crystalline plastics and sufficient wide ribs in highly loaded zones, the problem could be solved easily.
POLYMER FOAMS PRODUCED UNDER A TEMPERATURE GRADIENT
In a foaming process, it is known that temperature has a substantial influence on bubble nucleation and growth. In this work, the morphology and mechanical properties of a polyethylene foamed with azodicarbonamide is presented in the case where the material is placed in a temperature gradient. By controlling at different temperatures the top and bottom plates of a compression mold, it easy to control the density profile across the sample's thickness. The resulting morphology is shown to have an influence on the mechanical behavior of the foams under different types of loadings.
STUDY ON THE INDUCTION MOLD HEATING COMBINED WITH UNBALANCED COOLING TEMPERATURE CONTROL AND ITS EFFECT ON THE WARPAGE OF INJECTION MOLDED PART
Dynamic mold temperature control can achieve no weld-line and high gloss surface products. Since mold surface temperature variation history is different between core and cavity side, molded parts warped easily. In the study, artificial unbalanced cooling using five coolant temperature difference setting between core and cavity side and four various delay times of cooling water control is conducted in combination with induction heating (up to mold temperature 140 oC) to solve the part warpage. Part warpage can be reduced from 2.48 mm to 0.01 mm (99.8% improvement) by setting the cavity and core temperature is 20 oC and 80 oC, respectively.
SIMULATION AND ANALYSIS OF FIBER ORIENTATION IN INJECTION MOLDED BIPOLAR PLATES FOR FUEL CELL
This research took bipolar plate of Proton Exchange Membrane Fuel Cell (or PEMFC) as the study case, and used Moldex3D mold flow analysis software to analyze the flow of fiber material. The bipolar plate was fabricated through injection molding process, and observed the fiber orientation with Scanning Electron Microscopy (or SEM). This research used PA6 (Polyamide, Nylon6) and +40% carbon fiber. Fiber (Length 200?¬m / Diameter 10?¬m). Taguchi methods was utilized to analyze the experiment. It adopted fillet (round corner) design on the channel, and the finished product had a size of 100mmX100mmX3.6mm, and the channel was 1.2mm in its width and depth. Different injection process conditions were used: channel configuration direction (parallel and vertical to filling direction respectively), melt temperature, mold temperature, injection pressure, hold pressure, back pressure, injection rate and screw speed. Experimental factors were applied to mold test pieces and measured. The results of this research showed that the fiber would turn around and entangle together, and thus decreased the electrical resistance when the channel was vertical to the filling direction. The uniformity of resistance would be increased when the channel was parallel to the filling direction.
NEW INSIGHTS IN PVT-BEHAVIOR FOR HIGH PRECISION IN INJECTION MOLDING
The main impact factors on shrinkage and dimensional stability are the temperature and pressure the melt is subjected to during processing. Hence, pvT-behavior can be used to predict the dimensional deviations of plastic parts. Since large differences exist between predicted and actual shrinkage, a closer look was taken at the effect of pressure and pressurization on the dimensions of the part. For this study, fundamental examinations of the behavior of amorphous thermoplastics during compression and cooling were made. These include the analysis in the different phases as well as the variation of the pressuretemperature- cycles and their succession. It was found that the specific volume and therefore the thermal expansion coefficient and compressibility are dependent on the pathway of the process. In this paper, the results of these experiments are shown and the impact on the shrinkage behavior during injection molding is discussed. In the outlook the application of these insights in a new injection molding technology ƒ?? the Compression Induced Solidification (CIS) - is presented.
INVESTIGATION OF MOLD HEATING BY INDUCTION HEATING WITH EMBEDDED COILS WITHIN MOLD INTERIOR
The effects of coil to cavity surface distance on the heating efficiency of induction heating using embedded coils within the mold base is investigated. Simulation was also performed by integration of both thermal and electromagnetic analysis modules using ANSYS. For a 15 mm coil to cavity surface distance it takes 20 seconds for mold temperature to rise from 80?øC to 110?øC (1.75?øC /s heating rate), whereas for the 20 mm distance case mold temperature rise from 80?øC to 85?øC in 20 seconds (heating rate 0.25?øC/s). Simulation also shows good agreement with experiments.
MOLD SURFACE HEATING USING HIGH FREQUENCY INDUCED ELECTROMAGNETIC PROXIMITY EFFECT
High frequency induced electromagnetic proximity effect is used to achieve mold surface heating. A pair of flat mold plates (100 mm by 100 mm by 32 mm) was used for the experiments. When a high frequency current flows successively into the two mold plates, an electromagnetic proximity effect is induced between the mold plates and heats the mold surface. Simulation via ANSYS was developed by integration of both thermal and electromagnetic analysis modules. It takes 10s to heat the mold surface from 40oC to 80oC with a heating speed of about 3.68oC/s, and the simulation also shows good agreement with experiments.
PREPARATION AND CHARACTERISATION OF POLYVINYL ALCOHOL NANOCOMPOSITES MADE FROM CELLULOSE NANOFIBRES
A method had been developed using a combination of acid hydrolysis and ultrasound to obtain a high yield of cellulose nanofibres from flax fibres and microcrystalline cellulose (MCC). Polyvinyl alcohol (PVA) nanocomposites were prepared using these additives by a solution casting technique. The cellulose nanofibres and nanocomposites films produced were characterised using FTIR XRD TGA SEM and TEM. A significant enhancement in thermal and mechanical properties was achieved with low addition of cellulose nanofibres to the polymer matrix.
A DIRECT 3D NUMERICAL SIMULATION CODE FOR EXTRUSION AND MIXING PROCESSES
This work focuses on the development of ageneral finite element code called Ximex?? devoted to thethree-dimensional direct simulation of mixing processes of complex fluids. The code is based on a simplified fictitious domain method coupled with a ƒ??level-setƒ? approach to represent the rigid moving boundaries such as screws and rotors as well as free surfaces. These techniques combined with the use of parallel computing allow computing the time-dependent flow of generalized Newtonian fluids in large and complex processes involving moving free surfaces which are treated by a level-set/Hamilton-Jacobi method. Two flow case studies will be presented in this paper: the flow within a twinscrew extruder and the flow in a batch mixer.
BLENDS OF INFUSE' OLEFIN BLOCK COPOLYMERS FOR ADHESION TO POLAR SUBSTRATES
INFUSE' Olefin Block Copolymers (OBCs) are polyolefins with blocks of hard (highly rigid) and soft (highly elastomeric) segments. These materials break the traditional relationship of flexibility and heat resistance, while offering significantly improved compression set and faster cycle times in injection molding applications.However, adhesion of these polyolefin based materials to polar substrates remains expectedly poor, but blending with other polymers can improve adhesion performance. In this paper the structure-property relationships of Olefin Block Copolymer (OBC)-based blends that offer adhesion to polar substrates will be discussed.
EFFECT OF POLYMER FILM PERMEABILITY ON RETARDING OR PREVENTING CORROSION AND MOLD
Damage of products resulting from mold and rust contribute to millions of dollars of losses in a variety of industries. Rust and mold are affected by moisture in the surrounding environment; therefore it is critically important to control moisture vapor in order to prevent formation of rust and mold. Recently ionomers having novel performance (increased selective gas transmission while maintaining mechanical properties) have been developed. In this paper we demonstrate efficacy of these ionomers in preventing rusting and mold growth and discuss their use in film structures which have both good mechanical properties as well as appropriate gas transmission properties.
EFFECT OF POLYMER FILM PERMEABILITY ON RETARDING OR PREVENTING CORROSION AND MOLD
Damage of products resulting from mold and rust contribute to millions of dollars of losses in a variety of industries. Rust and mold are affected by moisture in the surrounding environment; therefore, it is critically important to control moisture vapor in order to prevent formation of rust and mold. Recently, ionomers having novel performance (increased selective gas transmission while maintaining mechanical properties) have been developed. In this paper, we demonstrate efficacy of these ionomers in preventing rusting and mold growth and discuss their use in film structures which have both good mechanical properties as well as appropriate gas transmission properties.
ACADEMIC POLYMER EDUCATION AS UNDERGRADUATE AND GRADUATE DEGREE IN IRAN AND THE WORLD
As a standalone program, polymer education started about 20 years ago in Iran, founded based on the experiences of a few academics who had accomplished their graduate education mostly in European universities. Now it seems that a re-evaluation of this program is required in comparison with other countriesƒ?? experiences in polymer education (e.g. a standalone polymer education program started 60 years ago in USA). Here, the situation of academic polymer education in Iran and ten other universities worldwide has been studied. The roots of polymer engineering as a Major program in Material or Chemical Engineering, as well as other issues such as the offering department, curriculum and cooperation with industry have been discussed and compared, in order to improve the polymer education situation.
SIMULATING THE FLOW LENGTH TO THICKNESS RATIO IN ULTRA HIGH-SPEED INJECTION MOLDING BY MOLDEX3D ANALYSIS
In thin-wall injection molding, due to the very fast polymer melt heat transfer to the mold wall, the melt solidifies quickly during the filling stage. In this study, ultra high-speed injection molding (up to 600mm/s injection speed) was conducted. A mold of spiral shape, 0.4mm thick, is used to measure the flow length under different filling speeds. Simulation by Moldex3D was also performed for verification. For injection speeds of 100 mm/s, 500 mm/s, 1000 mm/s and 1400mm/s, the corresponding experimental results for the flow length to thickness ratios are 335, 467.5, 605 and 640, respectively. The simulation results also show that different heat transfer coefficients affect the flow length through variable injection speeds. Slower injection speeds require a higher heat transfer coefficient, whereas higher injection speeds only require a lower heat transfer coefficient.
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