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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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.
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.
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.
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.
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.
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.
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.
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 (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.
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.
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.
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.
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.
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."
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.
The effects of replication and molecular orientation on optical properties of polycarbonates (PC) injection molded parts with microscopic v-groove features have been investigated on various injection molding conditions and different cavity shapes. For optical properties, the luminance of the injection molded parts has been characterized. The mold temperature had significant effect on the replication. The replication is closely related to the optical properties. It was found that the optical properties depended on replication in compared with molecular orientation.
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.
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