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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Study on Pressure Control Device to Improve Foaming Uniformity for the Injection Molding Microcellular Foaming Process
In the microcellular foaming process, cell structure and distribution are very difficult to control. This experiment was carried out using the variable geometry mold. We used a cavity pressure control device and a hot nozzle system causing the polymer melt front to flow more steadily. Modification of cell structure and surface flow sink was experimentally verified. The experimental results show that the parts have smaller cell sizes and more uniform cell distribution. The surface reflection increases 10 to 30 % as compared to the traditional process and achieves the optical specification of the backlight module.
Study on Hot Embossing Molding Process and Replication Effects with Different Aspect-Ratio Micro Channels
In this study, micro molding via hot embossing was applied to micro channels with different aspect ratios. The micro feature in the Ni-Co based stamp consists of a micro-channel array of approximately 51.56?m in depth and widths of 50?m, 30?m and 15?m, respectively. A PC film of 1 mm thickness was used as a hot embossing substrate. Effects of different aspect ratios and various molding conditions on the replication accuracy of micro channels were investigated. It was found that the accuracies of the micro-channels decreased at increased widths when depth was 51.56?m. Higher embossing temperatures and embossing force led to demolding problems and made the substrate become thinner than 1 ?. However, the molding performance also increased. In sum, higher embossing force and embossing temperatures could lead to higher molding accuracy for micro channels with different aspect ratios.
Study on Microcellular Injection Molded PP/POE and HDPE/POE Composites
This study investigated the effect of the Polyethylene-octene-elastomer (POE) content on the mechanical and thermal properties of PP/POE and HDPE/POE composites by microcellular injection molding. Batches of PP and HDPE with POE content of, 0 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt% for each material were prepared. Nitrogen was used as the blowing agent. DSC was used to study the thermal properties of the samples and SEM was employed to study the microstructure of the fracture surface. The results showed that as POE content increases, tensile strength and flexural modulus decreases. However, as POE content rises, impact strength is increased.
Microcellular Injection Molding of PP and PC/ABS with Precision Mold Opening and Gas Counterpressure
The injection molding of microcellular polymers is expected to be increasable promise for engineering applications. The combined effect of precision mold opening and gas counterpressure process produced uniform microfoam structure with a maximal cell diameter less than 10m /1/. The nature of microcellular PP and PC/ABS was analyzed. It was observed that the mechanical properties, the morphology and the application of microcellular PP were influenced by the degree of crystallinity and the conditions of foaming process. The viscoelastic behavior of materials and their correlation between process, foam structure and properties of PP foam and PC/ABS foam were investigated by DMA.
Smarter Materials Systems Designs for the Future
The term Smart Materials" has been coined to those materials which change behavior when stimulated by light pressure thermal electrical or magnetic fields. Early applications of smart materials are for example electrorheological fluids for clutches and piezoelectric sensors for airbags. The challenge is to create significant additional value to large plastics markets by bringing enhanced functionality through smart materials systems designs. Smart materials systems designs require integration of multidisciplinary skills from materials science through to fabrication and lifetime prediction. Here in this review we address the issues of advancing the technology of polymers into "smarter systems". In particular we identify the needs and challenges to create significant additional value to large plastics markets via smart materials systems designs."
Environmental Stress Cracking in Polycarbonate – Prediction of the Long Term Behavior by the Use of Short Time Tests
The environmental stress cracking is the most common failure reason of polymer parts during their use. There are already many tests to verify the stress crack resistance. Most methods use combinations of an external strain and aggressive liquids to achieve a quick test result. The extrapolation to longer time periods is only successful with the help of the expert knowledge of the raw material producers. The development of a new testing method enables a simulation of the material long-term behavior on the basis of a short time test of plastics under the influence of a medium.
A New Procedure for Dimensioning Plastics Parts with Similar Consideration of Tensile and Compression Values
Today, the usage of plastics extend also to fields, where they have to stand high compressive loads. Because of the lack of compression values, a technically safe and economically meaningful dimensioning is often a problem. The quantitative comparison of tensile and compression values within the underlying work has shown, that it is possible to calculate the compression behavior from the belonging curves under tensile load with the knowledge of only one compression curve. Further investigations concerning plastics pipes have shown, that the usage of material models, which are calibrated with both values from tensile and also from compression tests leads to a 30% saving of wall thickness.
Curing of Bisphenol M Dicyanate Ester under Nanoscale Constraint
It is well known that the properties of materials are affected by constraint at the nanoscale. Although thermosetting resins have been cured in the presence of nanoparticles and nanotubes, cure of thermosetting resins under the well defined nanoscale constraints imposed by controlled pore glass (CPG) or similar matrices has not been previously documented. In this work, we investigate the isothermal curing of bisphenol M dicyanate ester/polycyanurate under various nanoscale constraints, including in unsilanized controlled pore glass, in silanized controlled pore glass, and within an alumina nanofilter. Differential scanning calorimeter is used to monitor the evolution of the glass transition temperature (Tg) as a function of pore size and pore surface chemistry. Fourier transform infrared spectroscopy (FTIR) is applied to study the degree of cure of polycyanurate in the bulk state and under nanoscale confinement. For the glass transition temperatures of the polycyanurate networks cured in the silanized controlled pore glasses, only the nanoconfinement effect is observed; whereas for the material cured in the unsilanized controlled pore glasses, both the nanoconfinement and surface effects are observed. Furthermore, nanoscale constraint accelerates the cure of bisphenol M dicyanate ester. FTIR study confirms the full conversion of the polycyanurate networks under nanoscale confinement.
In-Mold-Graining in Thermoforming
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
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
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
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.
Novel Metal/Polymer Blends for Highly Conductive Applications
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
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
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
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
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.
The Effect of the Injection Point Location on the Fiber Glass Length
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
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
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.
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