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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Effects of Melt Rotation on Warpage Phenomena in Injection Molding
Shear induced imbalanced filling in a geometrically balanced runner system is always a difficult problem to handle in injection molding. Moreover, the shear-induced temperature variation across the cross section also affects the warpage result. Previous research proposed that the melt rotation apparatus could control the warpage phenomena of parts. In this paper, we have proposed a new methodology to analyze this injection process. The comparison between the simulation and experiments can demonstrate and verify the warpage phenomena. The results show that the proposed methodology is a highly valuable tool to understand the melt rotation effects.
Process Time Reduction in Blow Moulding Process with Conformal Cooling
This paper presents the design and application of novel straight conformal cooling channels in reducing the process time for blow moulding process using the finite element analysis. Different configurations of cooling channels are designed for a blow mould of a plastic motor oil bottle and they are tested by running steady state and transient thermal analysis in Pro/Mechanica Thermal software to predict the cooling time. Results are compared with conventional channels with modified geometry. Results predict that proper layout of cooling channels can reduce the process cycle time by around 44% compared to conventional cooling layout.
Intelligent Quality Prediction in Injection Molding
Quality of injection-molded parts is determined by a lot of factors, such as machine, plastic material, operation conditions and others. Normally, using numerical or experimental method to examine and control all parameters is still very difficult. In this study, we proposed a computational intelligence-based method to obtain the optimal process windows systematically. In addition to this, this method can be used as an on-line monitor to predict part quality from process dynamics data. This method combines design of experiment (DOE) and neural network techniques for intelligent quality prediction. This approach is a potential method to improve the molding stability and molded part quality.
Impact Performance of Pe Butt Fusion Welded Joints
Through this work the rapid crack propagation of PE butt-fusion welded joints was evaluated with impact tests performed on sharp notched specimens at varying temperature and test velocity. The effect of test velocity was studied by means of the impact strength at 20ºC and 1, 2 and 3.7 m/s. The effect of test temperature was assessed at 1 m/s where dynamic effects are small and allow the application of Fracture Mechanics techniques. The Impact Toughness, Jc, was determined in a wide range of temperature (–60 to 20ºC). Complementary, SEM was carried out on fracture surfaces to elucidate the deformation mechanisms acting. It was found that independent of the testing conditions, they were only slightly inhibited in the welded samples suggesting that fracture propagation was practically not affected by the welding procedure.
The Yielding of Propylene Polymers
The use of toughened propylene-based polymers in engineering applications has increased the demand for relevant data regarding yielding behavior in complex stress states. Through this work the yield behavior of polypropylene homopolymer, polypropylene copolymers and polypropylene elastomeric polyethylene mechanical blends was studied. This investigation proves that Modified Von Mises criterion provides reasonable predictions of the biaxial macroscopic yield behavior of these materials despite the inherent tendency of PP to deform by crazing. The incorporation of a second elastomeric-phase by melt blending or increasing crystallinity does not change the pressure dependency of PP polymers. The studied copolymers exhibited a more pronounced yield stress sensitivity to hydrostatic pressure than homopolymers and mechanical blends. Yielding envelopes decrease with increasing elastomer content in mechanical blends and enlarge with increasing crystallinity.
Crystallization Rate of Soft Segment on Shape Memory Effect in Shape Memory Polyurethane Ionomer
To illustrate the effect of crystallization rate of soft segment on shape memory effect in shape memory polyurethane (SMPU) ionomer, SMPU ionomers having ionic group within hard segments were synthesized. Isothermal crystallization kinetic method was used to analyze the effect of ionic groups within hard segments on crystallization of soft segment. Thermal cyclic tensile testing was conducted to investigate the shape memory effect. It was found that the ionic group in hard segments slows down crystallization of soft segment; when physical cross link is strong enough, the crystallization rate would be a predominant factor determining the shape fixity ratio after various cooling time; when physical cross link is weakening, the influence of crystallization rate is much less for cooling time dependence of fixity.
Experimental Validation of Numerical Simulation for Phase Decomposition of a Binary Polymer Thin Film on a Patterned Substrate
Phase separation of polymer blends can be directed by the difference of the attraction factors to the polymers on a patterned substrate to achieve polymer self-assembly. A 2D model of the Cahn-Hilliard equation was established using an unconditionally gradient stable time marching scheme. The morphology development in the early stage of the phase separation on a template guided self-assembly was investigated through numerical simulation. Through the numerical investigation, it was observed that the morphology evolution of the polymer blends depended on the consistency of the initial concentration, strength of forcing function, scaling factor, the gradient energy coefficient, and material properties.
Bulk and Nano Mechanical Properties of Surface Modified Polypropylene Films with Acrylic Acid as Grafting Agent
Polymeric films have become more attractive materials for multipurpose applications. In order to adapt them to several kinds of applications, extra functions keeping their bulk characteristics are desired. Modification of PP films through a grafting technique is considered to be one of the main routes to overcome their limitations avoiding coating delamination and without affecting bulk polymer properties. Through this paper the superficial nano-mechanical properties, bulk mechanical properties, and fracture behavior of surface graft copolymerized with acrylic acid PP films are reported.
Principals for Designing Medical Parts for Plastic Joining
Designing medical appliances for plastics assembly requires a comprehension of the various plastics joining methods, a knowledge of joint designs and material selection plus an understanding of their relationships.Medical devices comprise an elite group of parts within the plastics joining arena which have a unique set of finished assembly criteria. Strength requirements due to forces exerted on commonly small mechanical devices used in surgical procedures must be such that the assembled devices are failsafe during operations.Seal requirements of vessels must be hermetic to prevent leakage of gasses or liquids either in to or out of a chamber. Surface marking of the device must be nonexistent for not only cosmetic requirements but also for the ability of the device to slide freely over living tissue. Rough surface crevices may harbor bacteria and can not be tolerated.Understanding the principles of plastics joining, the capabilities of each method and proper implementation of the appropriate joint design, can provide the designer with a clear direction at the outset and a successful an repeatable assembly result for the part.
Opening the Pandora's Box to Find Elastic Breakup as the Origin of Various Nonlinear Flow Behavior of Entangled Polymers
Chain entanglement is an essential concept in polymer science. It has been explored for six decades since the 1946 transient network theory of Green and Tobolsky. Another three decades after the 1971 de Gennes' reptation idea have passed before a method has been devised in computer simulation to depict chain entanglement . More recently, the time-resolved determination of velocity profiles during and after shear of entangled polymers  have led to a specific molecular mechanism for chain disentanglement . This work describes the latest understanding on the subject of polymer flow.
Extruded PLA-LLDPE Films with Bi-Functional Blend Morphology Formed with a Continuous Chaotic Blender for Barrier and Toughness Improvements
A continuous chaotic (smart) blender was used to controllably produce a wide variety of morphologies in polylactide acid (PLA) - linear low density polyethylene (LLDPE) blends at LLDPE compositions of 20% and 30% by volume. The structured blends were extruded as films. In comparison to typical blends obtained by mixing consisting of droplets, results indicate that blend morphology can be selected with the chaotic blender to simultaneously improve permeability and impact toughness. Both properties benefit from high frontal area and interconnected shapes derived from multi-layers formed initially by the stretching and folding mechanism characterizing chaotic motions in the melt.
Influence of Polymer Matrix and Coupling Agents on Melt Flow Behavior of Wood Filled Polyethylene Composites
The influence of coupling agents on the melt rheological properties of HDPE/wood flour composites has been investigated in this work by means of a capillary rheometer. Scanning electron microscopy was also employed to supplement the rheological data. It was found that molecular weight and molecular weight distribution of the polymer matrix and coupling agent characteristics influence the melt flow properties of the filled composites. Generally, low molecular weight and narrow molecular weight distribution polyethylene matrix provides larger increase of the viscosity of the composites with respect to the unfilled resin. Coupling agents tend to increase the resistance to shearing, but wall slip effects may interfere with the measured values, especially at very high filler loadings.
Creating Gradient Refractive Index (GRIN) Lenses by Nanolayered Polymer Assembly
Fabrication of a new class of bio-inspired gradient refractive index (GRIN) lenses with an unprecedented variety of index gradient distributions is described. The fabrication of GRIN lenses is based on a method of polymer forced-assembly. Nanolayered films of PMMA/SAN17 were co-extruded from which flat GRIN sheets with pre-designed refractive index distributions were produced. GRIN lenses with no on-axis spherical aberration and good image quality were shaped from these sheets using conventional lens processing methodology.
Forced Assembly of Layered Polymers
A very exciting new field of interdisciplinary macromolecular science and engineering has rapidly emerged over the past ten years at the crossroads of polymer and materials science, engineering, chemistry, physics, and biology. This field of polymers plus" enjoins natural biological materials systems (lessons from biology) revolutionary new synthetic polymers with greater control of macromolecular and supermolecular architecture and innovative processing of polymeric assemblies. A recent breakthrough in the laboratories of Baer and Hiltner extends co-extrusion process technology to the nanoscalethereby making it possible to fabricate films with many thousands of layers.This extremely flexible process relies on forced-assembly to achieve nanoscale structure. The new National Science Foundation (NSF) Science and Technology Center for Layered Polymeric Systems (CLIPS) at Case promotes rapid growth of this nanoscale technology and facilitates its translation to the commercial sector through innovative research and education partnerships. The primary goals of CLIPS are to:Integrate research activities in three platforms with multi-level educational programs to train a diverse American workforce that can meet the challenges of the new nanotechnologiesFocus the impact of the integrated research and educational activities on national priorities in defense environment energy and healthDisseminate the knowledge developed through the integrated CLIPS activities to the larger audienceServe as a compelling model for expanding relationships between Historically Black Colleges and Universities (HBCUs) and research universitiesLessons from biology have revealed that natural materials systems have architectures that are specifically designed to accommodate a unique spectrum of required properties. These architectures always have many scale levels that are bound together by interfacial coupling or adhesion. In recent years new synthetic approaches have been used to develop materials systems with novel mechanical transport electrical and optical properties. Examples of hierarchical structures with unique properties developed with these films will be given. Since the radius of gyration of macromolecules can readily exceed the nanolayer thickness the surrounding layers can be used to impart dimensional constraint at the molecular level. Perhaps the most spectacular application of polymer nanolayers is our development of bioinspired axial cylindrical and spherical gradient refractive index (GRIN) lenses. These are made by layering nanolayered polymer films into hierarchical structures with controlled refractive index gradients. The spherical lenses biomimic the octopus lens. They contain more than 5 x 105 nanolayers. Lenses of this type exhibit a wider field of view with less aberration than conventional lenses having no index gradients."
Prediction of Theweld-Line-Induced Strength Reduction for Nylon6 and its Nanocomposites
The position and strength of the weld-line have important influences on injection molding plastic products qualities. This paper discussed the weld-line in Nylon6 and its nanocomposites by formulae. Utilizing linear regression, referencing existing self diffusion mathematics model, semi-experimental formulation was found to calculate the degree of bonding. The influence of thickness and processing parameters, such as melt temperature, mold temperature, holding pressure and injection velocity, were considered. Compared with experimental results of PA6 and nano-composite PA6 specimens with thickness 1.0mm, 2.5mm under different processing conditions, the maximum of error by formulas is 2.56% of PA6 and 1.78% of nano-composite PA6, respectively.
Effects of Processing Parameters on Optical Properties of Injection Molded Polystyrene Parts
In this paper, PS products qualities are discussed by experiments to find the relations between processing parameters and residual stresses, optical properties. Residual stresses are measured by polarimeter. The variance of processing parameters is considered when residual stresses distribution and polarimetric interference are measured. Also the optical property of transparency and haze are measured by transmittance meter. From the experiments results, we find that processing parameters have great effects on residual stresses and haze but little effects on transparency.
Influence of Geometrical Factors on Cavity Pressure during the Injection Molding Process
The influence of the thickness of plastic parts on the behavior of the cavity pressure during the injection molding was studied. The instrumentation of molds for a modification of a normalized test specimen for impact was proposed, placing pressure transducers in the more critical zones of the parts. The evaluation of the molds was made using solid modelator software in three dimensions and a simulator software of the injection process with different resins. The simulation results demonstrated that the thickness of a part affect the behavior of the cavity pressure during filling and post-filling phases, the cooling and the dimensional stability of the part.
The Influence of Processing Variables and Two-Way Interactions on the Weldline Strength of Injection Molded Parts
Strength is an important performance of the injection molded parts. Obtaining sufficient mechanical strength is quite needed for some parts. Weldline developing in the part significantly reduces the strength of the parts. Strength of the parts is affected by many factors. In this report, An L27 Orthogonal Array designed based on the Taguchi method was conducted to investigate the effect of process parameters and two-way interactions on the strength of injection molded parts with weldline and without weldline. The main effects of the factors and two-way interactions were estimated, and the relative significances of each processing parameter and interaction on the strength were analyzed.
Mold Cooling Analysis for Injection Molding Process Using Fast Multipole Method
Mold cooling process in injection molding is critical in order to reduce cycle time and improve the quality of molded part. In this paper, a fully three-dimensional mold cooling analysis is developed. Mold heat transfer is considered as cyclic-steady, three-dimensional conduction: heat transfer within the part is treated as a 3D transient heat conduction; heat exchange between the cooling channel surfaces and coolant is treated as a cycle-averaged steady state three-dimensional heat conduction. Numerical implementation includes the application of a hybrid scheme consisting of a 3D BEM based on FMM for mold region and a CVFEM for part. The FMM algorithm dramatically reduces the complexity of matrix-vector multiplication involving a certain type of dense matrix, which can arise out of many physical systems. The present analysis is then used to predict the temperature field for a 3D plastic part geometry.
Evaluation of Molecular Orientation of Weldline Region in Polycarbonate by Laser Raman Spectroscopy
Molecular orientation in weldline region in injection molded polycarbonate was investigated by polarized laser-Raman spectroscopy. The relative intensity ratio of two specific peaks in a spectrum was determined as an index of molecular orientation in accordance with an earlier report. The intensity ratio of the peaks showed the highest value at the point ca. 30 ?m apart from the V-notch at the surface of the specimen. The orientation direction was found to be parallel to the weldline. The birefringence, ?n, of this point was estimated to be 2.64×10-3 from the results of another study to determine the relationship between Raman peak intensity and birefringence. This value corresponded to ca. 2.5 % of the intrinsic birefringence of polycarbonate, 0.106. Meanwhile, the birefringence of V-notch itself was calculated to be 0.59×10-3, lower than that of the surroundings. Although a similar tendency was found at the area ca. 100 ?m inside from the surface, the birefringence itself was slightly lower than that of the surface. These results suggest that molecular orientation increases near the weldline due to convergent flow, while the molecules at the interface of the weldline relax. Thus laser-Raman spectroscopy provides some important clues to understand the flow behavior around weldline.
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