SPE Library

The flow patterns and injection pressures predicted using injection molding simulation software and actual flow patterns and injection pressures of the molded parts using a short study were compared and quantified. A method of validation was developed to compare the simulation results with actual molded parts and indicated that by using the correct combination of mesh type and certain process settings in the simulation software, an accurate prediction can be achieved with the simulation.

Flexural creep behavior of nylon 6/6 based long fiber thermoplastics (LFT) was determined using transient and dynamic testing methods. While the effect of increasing fiber volume fraction reduced creep, there was only a negligible effect of flow orientation effect. The creep data generated by dynamic mechanical analysis (DMA) tests was consistent with the transient tests.

Optically transparent nanocomposites were prepared via twin-screw extrusion of a medical-grade flexible PVC resin and an organically modified montmorillonite. Intercalation and orientation of the montmorillonite layers were observed via x-ray diffraction. A positive influence on barrier properties was noted, including a five-fold increase in oxygen barrier at minimal clay loading. Consistent with the literature, no significant changes in thermal stability in air were observed.

Porous polyester thermoset xerogels have been produced via sol-gel chemistry. The pore structure of these materials is tunable and can be altered independent of or in tandem with alterations in composition by adjusting solvent quality, solids content, and processing methodology. Cytocompatibility studies on selected xerogels imply effects of both pore size and materials chemistry, with fully aliphatic polyesters with large pore structures allowing for the growth of mammalian cells.

This paper undertook a numerical study to characterize expansion of extruded polystyrene foam blown with CO2. The effects of processing parameters on foam expansion outside filamentary extrusion dies were examined. Efforts were made to optimize the processing parameters for the achievement of highly expanded foams.

Based on the fusion behaviors of PVC, the influence of compounding route of PVC/Montmorillonite nanocomposites, on their properties, including flexural, tensile, dispersion, and morphology was studied. The experimental results indicate that both the extent of property improvement and dispersion of nanaoparticles in PVC/Montmorillonite nanocomposites are strongly influenced by the degree of gelation achieved in PVC compounds during processing.

Polyurethane elastomers were synthesized with ethylene glycol as chain extender. The macrodiol was poly(ethylene adipate) MW = 2000 ± 50. Two isocyanates were employed: 4,4- diphenylmethane diisocyanate (MDI) and 4,4’ - dibenzyl diisocyanate (DBDI), alone or as mixtures. Materials were characterized by DMA, DSC and WAXS. Changes induced by varying the type and the number of isocyanates and the order of their introduction were followed. Crystallinity was strongly reduced when DBDI was mixed with MDI.

The interfacial adhesive strength between hydroxyapatite (HAP) and poly(?-caprolactone) (PCL) were determined using T-peel tests. Their composite fracture toughness was determined using essential work of fracture concept. Electrospinning techniques were employed to obtain nanometer scale PCL fibers with and without HAP reinforcements which also create micrometer-scale porosity in the structure. The effects of HAP morphology and HAP content on mechanical properties were evaluated.

Orientation of polymer chains has been shown to have a major effect on component properties. The chain orientation at the end of fill of a component is different from most other areas. Overflows have been used in various areas of the plastics industry to improve weld line strength and provide a more consistent gas channel in gas-assist molding. This study will investigate if the use of overflows to change the orientation of the polymer chains provides a more capable molding condition.

Allowing engineering students to work with students of other disciplines offers them an experience they can take with them as they begin their career in industry. The college students take the project from concept to a manufactured product. At the beginning of the project, psychology students interact with sixth-grade students to determine the best features to include in a car. The marketing students will then create a display and video commercial for each car.

The purpose of this project was to determine the effect of overflow tabs on ‘affected area’. It was done because overflow tabs could prove to be very important in the medical industry, where tight tolerance parts are needed. Along with that industry, parts with limited gating locations could also use overflow tabs to provide more consistent flow throughout the part.

This study investigated a rubber-assisted embossing process for structuring thin polymer films. The main advantages of a rubber support instead of a hard counter tool include simplification of the embossing tool, protection of the embossing master, buildup of high pressure, and ease of mold separation. With rubber-assisted embossing, thin polystyrene films in a thickness of 25 ?m were accurately patterned with microgrooves of characteristic dimensions on the order of 100 ?m.

Water-assisted injection molding (WAIM) provides a new means to manufacture hollow parts at lower costs. However, little work has been done to understand how the polymer melt flows under applying high pressure water. Experimental investigations on the melt flow, especially the fountain flow during water-assisted melt filling in an emulated mold were conducted in this work. The experimental results revealed the formation of fountain flow during melt filling under applying high pressure water.

When screw speed is increased, barrel cooling will result to maintain control of the set product temperature. This can lead to barrel temperatures below the crystallizing temperature of the polymer, and a thin layer of frozen polymer can accumulate on the barrel walls. The analysis of this frozen layer or freezeout" condition and an analytical expression for estimating the layer thickness is presented along with supporting data."

For continuously extruded products, such as sheet and profile extrusions, thickness uniformity is a key quality factor, and it is directly linked to flow oscillations or flow disturbances at the die. Many sources of flow oscillations in the extrusion system are identified, and methods are shown on how to configure the melt delivery system to minimize their transmission to the die. These methods are illustrated with a model based on the theory of hydraulic transients.

Finite Element Analysis (FEA) is only as accurate as the material models employed and it must correctly represent application specifics for the FEA to be as precise as possible. Two areas of concern for FEAs of elastomers are cyclic versus non-cyclic testing, and, strain dependent models. Ideally the analyst should be able to choose a strain based non-cycled material model or cycled material model depending on whether the application is a static or semi-dynamic application.

Water-assisted injection molding experiments were carried out on newly developed equipment in our lab. The effects of four processing parameters, short-shot size, melt temperature, water injection delay time, and water pressure, on the water penetration length and residual wall thickness of water-assisted injection molded polypropylene curved pipe were investigated. The crystallization behavior difference between the beginning and the end of the water channel of the curved pipe was analyzed using differential scanning calorimetry.

Profile extrusion is a well-established practice in the polymer industry. Adaptation of profile extrusion to microfabrication, however, is difficult due to scaling-related process changes. Particularly, the effect of surface tension increases as size reduces and could significantly contribute to cross-sectional shape change in microprofile extrusion. In this study, the role of surface tension in microprofile extrusion was numerically studied and compared with that of die swell. Strategies were proposed to reduce the surface tension influence and produce precision microprofiles.

A new method of preparing polymer blends with nanoscale-islands is proposed. The polymethyl methacrylate (PMMA)/ polystyrene (PS) blend, which has PMMA slands dispersed in nanoscale order, was prepared by the method: dissolving MMA monomer and polymerizing the monomer in PS matrix could provide higher molecular weight of PMMA and create highly dispersed PMMA domains in PS matrix owing to gel effects and diffusion mixing. The resulting polymer blend was foamed with CO2. Nanocellular foam could be prepared using the polymer blend morphology as a template where bubble nucleation was localized in PMMA domains. The effects of blend ratio, foaming temperature and depressurization rate on bubble diameter as well as bubble density were investigated. The higher depressurization rate at lower foaming temperature made cell diameter smaller and the density larger. The higher PS composition in blend made the density larger. The cell 40-50 nm in average diameter and 8.5x1014 /cm3 was obtained as the finest nanocellular foams.

The U.S Army Armament Research, Development and Engineering Center's (ARDEC) Packaging and Support Division, Picatinny Arsenal, New Jersey initiated a Product Improvement Program (PIP) to solve the deterioration problem in the gasket of the metal/plastic containers for mortar ammunition. This PIP was funded by PM-Mortars. The PIP addressed gasket material properties including: durometer, hardness, compression set, impact resistance, and other physical properties (app. A). The goal was to find a gasket material that would improve the seal, long-term storage, and transportation capability of both the PA154 (120-mm) and PA156/PA157 (81-mm) metal/plastic containers. Four materials that were recommended by ARDEC's Warhead, Energetics and Combat-support Armaments Center (WECAC) Material Laboratory were ethylene propylene diene (EPDM), styrene butadiene rubber (SBR), neoprene, and natural rubber (60). In addition, natural rubber (40), currently used on the 120-mm A154 metal/plastic container, was used as a baseline. The 60 and the 40 are the durometer reading. A down select process would be used to determine the best gasket candidate by good performance in environment and material testing.Based on successful testing, an engineering change proposal (ECP) will be submitted to implement the best gasket material in both the 120-mm and 81-mm metal/plastic containers.