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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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.
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.
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.
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.
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.
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."
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."
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.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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