SPE Library

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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Conference Proceedings

In-Mold-Graining in Thermoforming

Edmund Haberstroh, Lennart Ederleh, May 2007

The feasibility of In-Mold-Graining (IMG) has been proven through initial applications. Despite this, there is still a lack of detailed knowledge about the correlations that ensure the uniform reproduction of structured mould surfaces in thermoforming. The processing of multilayer laminates for soft-touch applications constitutes an additional challenge. In this paper, a heating concept for trilaminate materials (grainable layer/foam layer/compact layer) is presented to ensure an optimum forming result through a selective temperature distribution over the thickness of the material. The local pressure conditions between the trilaminate and the mold surface are investigated as a dominating influencing factor with respect to product quality.

Enhancing Productivity of Solid-State Microcellular Panel Production by Partial Gas Saturation in the Retrograde Region

Krishna V. Nadella, Vipin Kumar, May 2007

In the production of microcellular panels by the solid-state constrained foaming process, the time needed for saturating ABS sheets with CO2 gas has been recognized as a bottleneck to developing a viable industrial process. Significant improvements in the productivity of this process are achieved by a) using partial (non-equilibrium) gas saturation and b) conducting the gas saturation in the retrograde region [1, 2]. Using a combination of these two approaches, the time required to reach the needed CO2 gas concentration in 4.75 mm thick ABS was reduced by 60%.Results on the panel density and the skin thicknesses achieved are reported and micrographs showing gradient microstructures are presented.

Simulation of the Die Swell behind an Orifice Die

Walter Michaeli, Björn Fink, May 2007

During the flow through an extrusion die the melt is deformed. Due to the viscoelastic behavior the melt stores portions of introduced shear and elongational deformation as stresses. At the die exit the stresses lead to die swell. The prediction of die swell is still a big challenge in plastics processing today. In an orifice die the flow conditions, stresses and die swell behind the outlet are calculated using the finite element analysis. Two different materials are modeled using different viscoelastic models. The calculated die swell is compared to experimentally measured die swell and the two different models are evaluated.

Enhanced Barrier Improvement for Pet-Bottles by Combination of Interior and Exterior Plasma Assisted Coating

Walter Michaeli, Dirk Binkowski, Andreas Hegenbart, May 2007

Even though PET-bottles gain more and more market shares one crucial point is their insufficient permeation barrier. To overcome this disadvantage and to extend the shelf-life plasma assisted coating is a well known technique, which is industrially used. The coating is either deposited on the interior or exterior of the bottle. Typically barrier improvement factors (BIF) around 4 can be achieved for the gas carbon dioxide (CO2). A combination of both techniques leads to a significant increase of the BIF. Hence the technology enables applications for even more sensitive goods.

Dynamics of Hot Runner Purging

Wipoo Sriseubsai, Nick R. Schott, May 2007

Purging of hot runners consumes an inordinate amount of time, materials and money. A study to get an efficient color or resin change makes use of the viscosity reduction by varying process parameters, and using purge additives that influence viscosity and self cleaning characteristics. This paper reports a part of a study on how that shear rate and the temperature in the hot runner manifold and barrel affect purging. The results show that very high and low melt temperatures in both of them affect purging. The best temperature setting is a low temperature in the hot runner manifold and a low temperature in the barrel.

Novel Metal/Polymer Blends for Highly Conductive Applications

Walter Michaeli, Tobias Pfefferkorn, May 2007

For many electro-technical and automotive applications plastics components have to fulfill enhanced demands on their electrical and thermal conductivity. A novel material combination of metal fiber reinforced thermoplastics and low melting metal alloys allows a significant increase in the maximum filler content and therefore in the electrical conductivity in comparison to just solidly filled polymers, because the low-viscous alloy is already molten during manufacturing. The material can be processed economically to complex shaped parts by conventional injection molding. The material composition, the processing behavior and the resulting part characteristics will be discussed in this paper.

Applicability of Advanced Constitutive Equations for Coextrusion Flows of Polyolefin Melts

M. Zatloukal, R. Pivokonsky, M.T. Martyn, P. Filip, May 2007

The fitting/predictive capabilities of three models (eXtended Pom-Pom, PTT-XPP and modified Leonov model) are tested for both, steady as well as transient shear and uniaxial extensional flows of mLLDPE and HDPE. The applicability of these constitutive equations has been investigated from the coextrusion flow modeling point of view. Finally, the FEM and modified Leonov model has been employed for the stress analysis in the coextrusion flow domain and predicted stress fields have been compared with the stress measurements from the flow coextrusion visualization cell.

Effect of Die Geometry on Foaming Behaviors of High Melt Strength Polypropylene with CO2

Patrick C. Lee, Wanrudee Kaewmesri, Jing Wang, Chul B. Park, Jantrawan Pumchusak, Rick Folland, Andreas Praller, May 2007

A systematic study is conducted to investigate the effect of die geometry (i.e., pressure and pressure-drop rate) on the cell-nucleation and growth behaviors of noncrosslinked high melt strength (HMS) polypropylene (PP) foams blown with supercritical CO2. The experimental results show that the cellular morphologies of PP foams are sensitive to the die geometry. The initial expansion behavior of the foam extrudate at the die exit is recorded using a high-speed CCD camera, which allows the study of die geometry effect on both initial expansion behavior and final cellular morphology. The effect of die temperature on the cell morphology is also studied.

Shape Memory Elastomers Prepared from Ionomer/ Fatty Acid Salt Compounds

Elise L. Kamieneski, S. Mandelbaum, P. Vemuri, R.A. Weiss, May 2007

Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and fatty acid salts, FAS, (ZnOleate),. Physical crosslinks in the ionomer that arise from inter-chain ionic interactions provide a permanent shape, while the crystalline low molecular weight FAS provides the means for a temporary shape. The material can be deformed above the melting point (Tm) of the FAS and the new shape can be fixed by cooling the material under stress to below Tm of the FAS. Polar interactions between the ionomer and the FAS stabilize the dispersion of the FAS in the polymer and provide the continuity between the phases that allows the crystals of the FAS to provide a second network of physical crosslinks.

Patterning of Conducting Polymers on Flexible and Insulating Polymeric Substrates

Ming Wei, Jia Shen, Carol Barry, Joey Mead, Sivasubramanian Somu, Xugang Xiong, Ahmed Busnaina, May 2007

In this work, we report the electric field assisted patterning of a conductive polymer, polyaniline (PANi), on an insulated and prepatterned template, followed by transfer of the pattern to a secondary substrate. Conducting PANi was selectively assembled on the negative electrodes of the template. After deposition, it was demonstrated that by compression molding, patterned PANi can be transferred to a polyurethane film. Unlike transfer by solution casting, however, the transfer of patterned PANi by compression molding was not complete. This may be the result of poor mobility of the polymer molecules. This work provides a promising nanomanufacturing approach for cost effective and high performance flexible nanoelectronics and biosensors.

An Experimental Study on Shear Stress Characteristics of Polymers in Single-Screwextruders

Atakan Alt?nkaynak, Mahesh Gupta, Mark A. Spalding, Sam L. Crabtree, May 2007

Frictional forces (for temperatures less than melting or devitrification temperature) and viscous forces (for higher temperatures) have important roles on solids conveying and melting processes in single-screw, plasticating extruders. These forces are related to the shear stresses at polymer-metal interfaces. This paper presents the shear stresses and melting fluxes at four sliding velocities and at temperatures ranging from ambient temperature to 230°C for LDPE, ABS, HIPS, and LLDPE resins at a fixed pressure of 0.7 MPa.

Advances in Adhesion with CO2-Based Atmospheric Plasma Surface Modification

Rory A. Wolf, May 2007

The use of gas and/or liquid-phase carbon dioxide (CO2) with atmospheric plasma discharge surface pretreatment technology can remove micron and submicron particulates and hydrocarbon-based contaminations on plastics and metals. The cleaning process is based upon the expansion of either liquid or gaseous carbon dioxide through an orifice. The paper provides an understanding of the basic removal mechanism and provides experimental evidence of remarkable adhesion improvements relative to a broad range of applications in electrical, medical, and automotive manufacturing communities.

The Effect of the Injection Point Location on the Fiber Glass Length

S.L. Villarroel, R.A. Morales, M.V. Candal, A. Gordillo, May 2007

The objective of this study was the development of a methodology to evaluate the influence of the fiber glass length contained in injection molded, flat PP specimens. The initial fiber length used was 12 mm. Flat specimens with 1mm of thickness were injected varying the injection conditions (injection velocity, melt temperature and cycle time). The mechanical properties were evaluated in longitudinal and cross-sectional sense respect to the flow direction in a universal testing machine, varying the position with respect to the injection point. When the cycle time and melt temperature were increased, variations in the size and fiber length distribution were not observed.

Polyvinylidene Fluoride Containing Long Chain Branching for Blown Film Applications

Nafaa Mekhilef, Sara Reynaud, Lotfi Hedhli, Gilberto O. Pasquariello, May 2007

In this work the effect of long chain branching in polyvinylidene fluoride on its rheology and blown film processing is investigated. Branched samples prepared by a conventional polymerization process were compared to commercial resins in terms of their rheological properties in shear and extensional flows. The branched samples showed an enhanced elasticity allowing a higher melt strength as well as strain hardening when subjected to extensional deformation. The enhanced rheological properties in the branched samples resulted in better processing performance in a blown film application where higher blow-up ratios and thinner films were achieved.

High Melt Strength Polyvinylidene Fluoride for Thermoforming Applications

Nafaa Mekhilef, Lotfi Hedhli, Sara Reynaud, Gilberto O. Pasquariello, May 2007

This paper discusses the properties of high melt strength polyvinylidene fluoride (HMSPVDF) and their correlation with the thermoforming process. Resins having different molecular weights and extents of chain branching (CB) were prepared and compared to commercial resins considered linear polymers. The presence of chain branching enhances in the melt strength of the branched samples while the melt viscosity remains identical to the reference samples. HMSPVDF also shows a significant improvement in sag resistance over the reference samples and suggests better performance in thermoforming.

Interfacial Interpretation of Autohesion of Ethylene/1- Octene Copolymers by Atomic Force Microscopy

Hailing Yang, Wei Zhang, Ronald, D Moffit, Thomas C. Ward, May 2007

The T-peel fractured surfaces of bonded ethylene/1- octene copolymer films were characterized using atomic force microscopy (AFM) and analyzed by fractal analysis. A stitch-welding" autohesion mechanism was proposed on the basis of that fractal analysis results suggesting that amorphous chains interdiffused while unmelted interfacial crystal structures remain essentially unaltered during the autohesion process. The fractal dimensions and the characteristic sizes determined from the fractal analyses are strongly dependent upon 1-octene content bonding temperature and peel rate."

Numerical Simulation and Moldability Investigation of Micro-Features

Shia-Chung Chen, Li-Chi Su, Cheng-Yi Chang, Hsin-Wei Hung, Wen-Hsien Yang, May 2007

In micro-injection molding, the preservation of precise micro-feature is one of the most important indications to ensure proper functionality and quality. A new technique, Induction Heating" which is advanced in heating up the mold quickly and accurately is adopted to control mold temperature during filling phase. This paper aims to analyze the technique specifically for a part with micro-feature of a high aspect ratio. Meanwhile it probes into the result of numerical simulation and actual experimental investigation. The result shows that some critical factors have a dominant effect on the molding mechanism and this result will be beneficial to the development of micro-injection molding technology."

Efficiency Gains and Control Improvements Using Different Barrel Heating Technologies for the Injection Molding Process

Bruce F. Taylor, Timothy W. Womer, Robert Kadykowski, Robert A. Sickles, Jr., Luke A. Miller, May 2007

This paper compares the energy efficiency and control response of band-heaters with a new technology that uses non-contact induction to heat the barrel directly through an interposed layer of thermal insulation. Quantitative results from both laboratory injection molding machine runs and bench-top tests are reviewed. The effect of barrel diameter, surface condition and band-heater type on efficiency and control response are also considered, as are the implications of thermocouple depth.

Numerical Simulation and Experimetal Investigation of Fiber in Injection Molding

Hsien-Sen Chiu, Ya-Yuen Chou, Wen-Li Yang, Chia-Hsiang Hsu, Yamabe Masashi, May 2007

A lot of plastic parts are made of fiber-reinforced engineering materials for its superior mechanical properties. Since the flow induced fiber orientation is complex 3D behavior, the final properties of the injected parts become very complicated. In this research, a ribbed flat plate geometrical model is conducted to examine the effect of fibers with various design consideration on injected parts both numerically and experimentally. Results show that the flow induced fiber orientation both numerically and experimentally in a good agreement. Also, it shows the fiber orientation will affect the final injected parts significantly.

CO2 and Water Vapor Permeability in Polymer Nanocomposites and Foams

Zhihua Guo, L. James Lee, David L. Tomasko, May 2007

Permeation properties are important for the design and implementation of polymer nanocomposites and polymer nanocomposite foam products. The literature is quite limited regarding permeation studies on these materials. In this paper, we focus on permeation properties of polystyrene nanocomposites (two types of nanoclay and carbon nanofiber) and their respective foams. Commercial instruments (PERMATRAN-C Model 4/41 and PERMATRAN-W Model 3/33 from Mocon) were used to measure steady state permeability coefficients of CO2 and water vapor at three temperatures: 10°C, 25°C, and 40°C. From these data permeation rates and permeation activation energy are compared based on nanocomposite morphology.