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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Collaborative Navigation System for Concurrent Mold Design
As products become ever more diversified, their life cycles are growing shorter. To reduce production costs, increased process automation and concurrent design are priorities. Therefore, a collaborative integrated design system is crucial in the mold design and manufacturing process.This research develops a collaborative navigation system for concurrent mold design within the CAD browser, using Pro/Web.Link as the core tool. Providing both concurrent engineering and collaborative design functions, the navigation system is capable of assisting designers in accomplishing 3D mold development efficiently and accurately. Results show significant time savings over other mold design process methodologies.
A 3-D Thermal Model of Laser Transmission Contour Welding for a Lap Joint
The paper presents a three-dimensional (3-D), transient, thermal finite element model of a scanning laser transmission welding (LTW) process for a lap-joint geometry. The model incorporates an accurate representation of a laser beam which accounts for its spatial intensity distribution as well as scattering by the semi-crystalline polymer. The laser heating is treated as a time- and space-varying internal heat generation source. Laser energy absorption is considered in both the laser-transparent and laser-absorbing parts being joined. The absorption coefficient for the transparent part is derived from data in open literature. Absorption by the soot in the absorbing part is based on theoretical predictions of soot particle absorption using Rayleigh theory. Available experimental evidence (weld line width observations) supports the validity of the temperature distributions predicted by the model.
Microfabrication of Polymer Substrates for Lab-On-A-CD Applications
It has been demonstrated and studied by several investigators that embossing with localized heating of conventional polymer substrates can generate relatively high quality features, but in all cases, flash is generated. In this work, foamed substrates were studied using localized heating and the resulting features were free of flash. In this study, ultrasonic heating was selected and features embossed on several different microcellular foamed polymer substrates. Samples were fabricated to mimic standard compact discs (CD) that could be used for bio-sensing. Patterns of micro features were designed and developed to function as devices such as valves, mixing chambers for sample/reagent loading.
A Knowledge-Based Navigation System for an Integrated Mold-Design Process
Efficiency and quality are essential demands in mold and molding manufacturing. Most related enterprises have already expanded from 3C (Computer, Communication, Consumer Electronics) to 4C (3C, Car) products, characterized by small quantities and variety. For many firms, the shortened life cycle of products presents an unprecedented challenge.This research aims at developing a knowledge-based navigation system for an integrated mold-design process. Based on both customizable and standardized procedures, the system not only prevents probable engineering mistakes and accumulates valuable knowledge, but also shortens mold-design processes from 7~10 days to 2~3 days. It includes conceptual mold-design, core and cavity design, mold-base design, and 2D drawing.
Use and Design Considerations for Using an Industrial CO2 Laser for Trimming Thermoformed Parts
This Paper explores the use of a CO2 laser to trim thermoformed parts. Traditionally thermoformers trim their parts with saws, router, or die cutting. These methods can be costly and hazardous, particularly for small volume parts. Many accidents occur in factories and other workplaces using saws and other cutting machines. Because of the high accident rates associated with these activities, factories are looking for safer alternatives.Results from experiments using an industrial laser to trim two different parts are reported and conclusions are drawn about the types of parts best suited to this technology.
Molecular Dynamics Simulation of Deformation Behavior of Carbon Nanotubes under Generic Modes of Loading
Molecular dynamics (MD) simulation of single walled carbon nanotube (SWCNT) was carried out under generic modes of loading. All calculations have been performed on an (7, 7) armchair SWCNT. The diameter of SWCNT was ~1 nm while its length was ~6 nm. In modelling the SWCNT, the Tersoff-Brenner potential was used for bonded interactions and L-J potential was used to account for non-bonded interactions. The displacement boundary conditions were applied at top four rings of the nanotube while other end was kept fixed during simulation. A good agreement was observed in the results obtained through MD simulation with the analyses done using continuum shell theory for compression and bending. The Young’s modulus under these modes is ~ 5±0.6 TPa.
Effects of Processing Conditions on the Foaming Performances in the Polyolefin Insulated Coaxial Cable Extrusion
Coaxial cable is the cable that transmits electrical energy and singal from the receiver evices to the antenna in the base station. Nowadays, as the telecommunication technology develops, demand of high signal quality is required in coaxial cable. To meet this market requirment, it is necessary to develop a new cable which has a reduced signal power loss. The attenuation is attributed mainly to the copper in low frequency, and as the freqeuncy increases, occurs from the insulation. Therefore, the most effective method to reduce the attenuation in cable at high frequency is to improve the dielectric properties of insulation. In this study, a new lowloss cable was developed by improving the foaming degree of PE insulation. An optimization of resin compositions and foaming processing conditions was performed. The newly developed coaxial cable has 6~8% lower attenaution values compared to the conventional cable.
Influence of Screw Elements on the Processing of Preparing LDPE-g-MAH by Reactive Extrusion
The effects of screw configurations upon grafting of low density polyethylene with maleic anhydride initiated by dicymyl peroxide in a co-rotating twin screw extruder have been investigated. Grafting degree of the samples collected from three different positions on the screw and the exit of the die was evaluated by titration. The results showed that the screw configuration has a significant impact on the grafting process. The effects of the screw element structure upon reaction could be interpreted in two terms: conveying ability and mixing capability. Small conveying ability (i.e. large conveying resistance, uch as in reversed kneading blocks) would lead to a high degree of fill in the screw channel, resulting in a long residence time and a high degree of reaction. Intensive mixing, especially elongational mixing (such as in the long lead elements), tends to enhance the ingredient uniformity in the reactive system, and facilitate the grafting process.
Effect of Polarity on Electrospinning Polycaprolactone Tissue Engineering Scaffolds
Electrospun polycaprolactone (PCL) fabric was affected by the electrospinning voltage polarity. The tensile test breaking strain and breaking stress of negative polarity spun samples was half that of positive polarity samples. The differences were investigated using XRD, DSC, scanning electron microscopy (SEM), and mercury porosimetry. XRD found a peak of a different magnitude, but DSC found no significant differences in crystallinity. The SEM show few differences, but the porosimetry shows a different distribution.Recent articles by P. Supaphol (2), (3) challenged the assumption that there is no effect of high voltage polarity on the electrospinning (Espin) process and product. This study examined the effect of polarity on the mechanical and physical properties and processing of Espun polycaprolactone (PCL) in acetone. The ultimate tensile test results were startling: the negative polarity samples broke at one half the elongation, 28% vs. 60%, and only achieved a UTS of 0.23 MPa, one half the positive polarity’s 0.51 MPa. While the total porosity of the samples was insignificantly different (74.5%+/-1.3% positive and 77.4% +/-1.8% negative), the distribution of pore sizes determined by mercury porosimetry was less uniform for Positive samples ,with a strong peak at 5 ?m. The Espin process differed also: more (39%) of the PCL was attracted to the target and its edges when the polarity was positive vs. only 31% when the polarity was negative. However, the negative polarity put more PCL onto the front of the target, 45% vs. 39% for positive, leaving the front samples of similar thicknesses and average porosities. These properties of the fabric were significantly different in ways that may affect its use as a tissue engineering scaffold.
Synthesis and Properties of Telechelic Poly(Lactic Acid) Ionomers
A chemical recycling process was used to synthesize ?- and ?,?-(metal carboxylate) poly(lactic acid) (PLA) ionomers. Telechelic PLAs containing carboxylic acid groups, which were neutralized with appropriate metal acetates to produce Na-, Li-, K-, Zn-, Ca- and Y-?- and ?,?-telechelic PLA ionomers. Functionalization of the PLA was confirmed by FT-IR and 1H-NMR. In general, the Tg and Tm of the ionomers increased with molecular weight (which also lowered the ion-concentration) and ionization of the carboxylic acid. For a fixed molecular weight, the increase in Tg and Tm were linearly dependent on the ratio of q/a, where q is the cation charge and a is its ionic radius. Crystallization behavior was dependent on the ion concentration and location of the metal ions. The presence of the ionic groups increased the modulus of the polymer and the largest changes were observed with multivalent cations. The ?-(Y carboxylate) PLA even displayed a rubber-like plateau in its softening behavior.
Lexan* DMX Grade Resins – Scratch Resistant, Barrier Polycarbonates
Polycarbonates are widely used in injection molding applications because of their impact resistance, optical clarity, heat and chemical resistance. However in some applications, they lack the scratch resistance needed to maintain surface aesthetics of parts subject to constant handling. Lexan* DMX grade resins (hereinafter referred to as DMX") have been developed to offer significantly better surface hardness compared to standard polycarbonate thus potentially eliminating the need for secondary coatings operations. These transparent resins also possess oxygen and moisture barrier properties which makes them attractive for packaging applications."
Influence of Staggering Angle of Kneading Block on Phase Morphology of Immiscible Polymer Blends in Co-Rotating Extruder
The influence of kneading block configurations on the phase morphology of immiscible polymer blends (HDPE/PS) in a co-rotating twin-screw extruder had been studied. The thermal property and morphological structures of the samples were investigated by Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM), respectively. The results showed that the placement of kneading blocks in the melting zone leads to a narrow distribution of the minor phase diameter, whereas the presence of kneading blocks at the melt conveying region results in a small dispersed phase size in the blends.
Recycled Poly (Ethylene Terephthalate) (PET) Blends for Hot - Fill Bottles
Injection stretch blow moulded PET bottles offer glass like clarity, excellent gas barrier properties and good overall mechanical strength. However, PET bottles required for hot-fill (85 oC ) applications have encountered limitations due to its relatively low glass transition temperature.In this study, two virgin PET grade materials are blended with post consumer recycled PET. The heat-setting technique is used for the manufacturing of injection stretch blow moulded bottles for ‘hot-fill’ applications. The process parameters (the preform temperature, the heat-setting timing and blow mould temperature) and the blend ratios for PET bottles are optimised based on thermal and mechanical characterisation.
Hybrid FEM/FDM Approximation for Single Screw Extrusion
The hybrid FEM/FDM was employed for simulating the melting performance in a single screw extruder. The enthalpy formulation for the energy equation was used in solving the melting problem. The liquid fraction was introduced to establish the phase change between the melts and the solid bed. The simulation results were compared with the experimental results reported in the literature. Although the hybrid FEM/FDM precluded the explicit treatment of the location of the melt pool, fundamental pressure-drop flow rate relationships details of local shear rate, and macroscopic energy production seemed to provide a reasonable correlation between the predicted and experimental results.
The Effect of Interfacial Strength on the Light Refraction in Multi-Step Plastic Optical Fiber
The effect of adhesion strength at the interface of core layers on the light refraction was determined in multi-step index plastic optical fiber (MSI-POF). The multi-step refractive index profile in MSI-POF core was introduced by the combination of various methyl methacrylate (MMA)/fluoroalkyl methacrylate (FAMA) copolymers. The refraction angle at interface decreases with increasing FAMA content in copolymers and as a result, the light in MSI-POF propagated similar to the graded index plastic optical fiber (GI-POF). Adhesion strength at the interface of copolymers affects the light transmission path in MSIPOF. This might be minimized by achieving appropriate adhesion strength at the interface between core materials.
Investigation of Film Blowing Process Stability for Metallocene Based LLDPE with Different Level of Long Chain Branching
The effect of processing conditions, die design and material characteristics on the stability of the film blowing process has been investigated theoretically by the recently proposed Zatloukal-Vlcek model [Zatloukal M., Vlcek J., J. Non-Newtonian Fluid Mech. 123, p. 201-213, 2004; Zatloukal M., Vlcek J.: J. Non-Newtonian Fluid Mech. 133, p. 63-72, 2006] and the theoretical predictions were compared with the corresponding experimental data. It has been found that the model predictions are in good correspondence with the experimental reality.
Processing Fine-Celled Recyclable CBA-Based Polyolefin Foams in Compression Foam Molding
This paper focuses on understanding the technological potentials for producing recyclable polyolefin foams by using a modified technique of the conventional compression molding process, referred to as compression foam molding. A two-step compression foam molding method is being developed. The main processing feature of this method is that it allows for complete sintering of the non-foamable resin prior the activation of the CBA. First, completely sintered intermediate foamable products that have no pre-decomposed CBA particles and entrapped air bubbles are manufactured. Second, these intermediate products are used in the actual foaming process. The principal advantage of this compression foam molding method is that it produces high quality recyclable foamed structures with high volume expansion ratios by avoiding the need for cross linking.
Study of Residual Birefringence in Injection Molded Lenses
Injection-molded lenses have been widely employed for 3C products more recently. In this paper, 3D CAE flow analysis embedded with DOE methods have been adopted for studying lenses molded with cyclic-olefin-copolymers together with residual birefringence measurements. In addition, thermal annealing experiments have been performed on the relaxation effects on thermal history for further studies. Results have shown that shear stresses as birefringence are contributed by melt temperature and injection speed during filling; while, dimensional errors on optical surfaces of lenses have been influenced by melt temperature and holding pressure during the packing and cooling.
Screw Element Characterization in an In-Line LFT-D Process
Studies have been done on three different elements (mixing element and kneading blocks) to determine their influence on fibre length and wetting properties during an in-line direct compounding process using glass fibre with PP at a nearly constant specific output. Effects of individual elements could be ascertained by using only 6D length of the barrel. At 30wt% loading, the screw element geometry plays a dominant role in fibre length distribution. At 50wt% loading, fibre length is influenced mainly by the screw speed. SEM analysis results of the samples are provided. Characterization of the individual type of elements can be used as guidelines in future application.
A Compressible Model for Three-Dimensional Melt Filling and Gas Penetration in Gas-Assisted Injection Molding Processes
The numerical prediction of three-dimensional melt filling and primary gas penetration in a clip-shaped square tube is conducted using compressible models in this paper. Similar to other fully three-dimensional methods, the full Navier-Stokes equations are solved together with the front transport equation using a front capturing approach. Different from previous studies assuming incompressible fluids in the filling process, the gas compressibility is considered in the proposed compressible model. For the case of a clip-shaped square tube, the gas penetration length and gas core size are compared among numerical predictions and experimental measurements, where a 3D Hele-Shaw model is also presented. The proposed compressible model has much better prediction accuracy than the 3D Hele-Shaw model. The proposed compressible model in the present study is proven to be accurate in the three-dimensional simulations of melt filling and primary gas penetration problems.
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