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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Cyclic Data Leads to More Accurate Finite Element Analysis
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.
Penetration Length, Thickness and Crystallization Behavior of Water-Assisted Injection Molded Part
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.
Shape Changing Mechanisms in Microprofile Extrusion
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.
Preparation of Nanoblend Polymer by Polymerization in Polymer and its Nano Cellular Foams
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.
Optimization of Gasket Materials for Packaging Containers
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.
Chemical Recycling of Pet with Solid State Shear Pulverization Technology
Post-consumer PET (polyethylene terephthalate) bottles have been recycled into film and sheet products ever since the Containers and Packing Recycling Law came into effect in 1997. There has been a growing need, however, for a chemical recycling process. In this process post-consumer PET bottles are recycled into monomers that can be used as feed stocks for the recycled production of PET bottles for beverages. This paper reveals a chemical recycling process using an alkali solution in order to depolymerize PET material in to its monomers (terephthalic acid and ethylene glycol) within a short time. Unlike ther researchers, we did not use the flakes of PET, but used powdered PET produced based on solid state shear pulverization (SSSP) technology to achieve maximum yield (98%) and purity (95%) of the monomers in a short reaction time. The powdered PET has unique physical properties that affect experiment conditions temperature and pressure. The resulting terephthalate salt was treated with sulfuric or hydrochloric acid to yield highly pure terephthalic acid. Results show that the best percentage conversion of PET flakes is 1.5mol/l NaOH for 2 hours in 200 °C and for PET powder 1 .5 mol/l NaOH for 1.5 hours in 150 °C.
UV Curable Ink-Jet Formulations for the Ever Expanding Realm of Industrial Applications
Digital inkjet printing has escaped the traditional confines of the graphic arts market and exploded into the realm of industrial applications. UV curable inkjet inks are enjoying the fastest growth due to their instantaneous cure, excellent jetting, and green" attributes. The industrial possibilities are limitless and each application requires a specific ink formulation to meet precise requirements. The inks must demonstrate robust characteristics including high flexibility and elongation abrasion resistance adhesion to a myriad of substrates including metals low surface energy plastics glass and ceramics as well as excellent lightfastness and rapid curing. This paper explores the challenges that a formulator encounters while pursuing industrial opportunities and offers suggestions to create inks that are a perfect match for each application."
Dynamic Mechanical and Dielectric Properties of Polypropylene Nanocomposites
In this work we report on the investigation of the dynamics of maleic anhydride grafted polypropylene (PPgMA) and PPgMA-based nanocomposites by means of dielectric relaxation spectroscopy (DRS) and dynamic mechanical thermal analysis (DMTA). We study the effects of different PPgMAs on the miscibility with the organoclay, and examine the effect of organically modified silicate filler on the dynamics of PPgMA. Our results suggest that the _-relaxation process, corresponding to the glass transition of PPgMA, is significantly affected by the clay loading. The increase in Tg is a direct result of polymer-filler interactions that reduce the polymer chain mobility. Furthermore, in the nanocomposite materials a separate high-temperature process due to Maxwell-Wagner-Sillars (MWS) polarization was observed with dielectric relaxation spectroscopy.
Efficiency of Graphite Additives on Friction and Wear Properties of Sintered Polyimide
The lubricating effect of graphite additives depends on the moisture content: under dry conditions graphite provides high friction and needs water molecules for smooth sliding. When used as internal lubricant for polyimide, also the chemical reactions in the polyimide bulk seem important. The inefficiency of graphite at low temperatures is related to hydrolysis reactions in the polyimide bulk, lowering the effective water content in the sliding interface. Imidisation at higher temperature allows for water supply by condensation reactions. Chemical reactions are demonstrated by Raman spectroscopy. Wear of graphite-filled polyimide manifests either as cleavage along the basal planes or embrittlement.
Novel Material Properties for Medical Applications via Ionizing Radiation
Traditionally, the medical device industry is concerned with degradation aspects of ionizing radiation with sterilization. However, these same radiation sources can also be used to create material properties un-obtainable by other methods. For example, radiation crosslinking produces packaging films from low melting polyolefins to render them steam autoclavable, or undergo minimum distortion at temperatures as high as 125° C. Or, soft, flexible material with extremely high toughness for angioplastic surgery created with high doses of radiation. In assembly operations, components with dissimilar materials can be joined in seconds upon the application of short wavelength ultraviolet radiation. In this presentation, we'll introduce the subject of radiation interaction with polymeric materials, using our own examples and commercial success stories to illustrate the utility of these radiation processes. In the mean time, a critical comparison will be made on the relative merit and disadvantages of each radiation source.
Design of Experiment to Optimize Absorber in Resin Welding Parameters
Through Transmission Laser Welding can be accomplished using either a coating or a weldable resin. As part of the weldable resin work, it was necessary to conduct a series of experiments to define optimum welding parameters. In one study, a DOE was conducted to determine the optimum welding parameters for polycarbonate and to develop a prediction equation which could be used in other tests. This DOE studied the effects of absorber concentration, energy density, thickness and pressure. The ability to weld the PC was achieved by blending a Clearweld® infrared absorber with PC resin and molding the parts into a weldable form. This paper summarizes the test procedures and results of the DOE.
The Effect of Mold Temperature on Morphology and Mechanical Properties of Injection Molded Hdpe Structural Foams
In this study, HDPE structural foams were produced by injection molding under different mold temperatures to study the effect of this variable on average cell dimension, cell density, and skin thickness ratio. Samples were also produced by setting independently the temperature of the fixed and moving plate of the mould to detect the sensibility of foam structure to a temperature gradient in processing. The resulting foams were also characterized in terms of mechanical properties including impact and flexural tests. It was found that for homogeneous mold temperatures, symmetrical skin thicknesses were obtained, which increased with decreasing mold temperature. On the other hand, by keeping one mold face at a constant temperature and varying the second one, asymmetric skin thicknesses were obtained. The degree of asymmetry was found to increase as the temperature difference between both molds increased. Furthermore, decreasing mold temperature produced a small increase in average cell sizes and reduced cell density. In general, both impact strength and flexural moduli of the structural foams increased with increasing skin thickness. For the particular case of asymmetric foams, the moduli were slightly dependent on the direction of the applied force (surface on which the stress is applied). Higher impact strength was obtained when the falling weight stroke the samples on the face having the smaller skin thickness, whereas for flexural tests, the reverse was observed.
Optimizing Pad Printing Efficiency with Stepper Motor Technology
Technology tends to advance in fits and starts, and pad-printing equipment is no exception. New machinery is developed by manufacturers either as a means to overcome specific technical hurdles or in response to competitive pressures. In this paper we'll look how the old technology of pad-printing has learned new tricks when confronted with both of these issues. And we'll explore how improved equipment designs are opening doors for the pad-printing process in industrial-imaging applications. In particular, we'll consider large-format applications involving consumer appliances, where new pad-printing machines are making the technology viable as an alternative to in-mold decorating, heat transfers and pressure sensitive labels.
An Optimization Approach for Polymer Sheeting Die Design
An optimization approach for the polymer sheeting die design based on the finite element simulation and genetic algorithm was studied in this paper. The optimization model was established according to the flow balance principle where the outlet flow distribution uniformity was taken as the optimization object and the die structure parameters were the design variables. The results of FEM simulation on the polymer extrusion process were adopted for the calculation of the objective function. The genetic algorithm was used for the fitness evaluation and the search of optimal design variables. The above optimization approach is applied for the optimal design of a fish-tail sheeting die whose result shows that it's feasible and reasonable.
Rheological and Crystallization Behavior of Linear and Branched PBT
Rheological and thermal characteristics of PBT resins were investigated with potential applications in low density foaming. The branched PBT was produced by extrusion modification with a tri-functional modifier, whereas the linear PBT was processed under the same condition without the modifier. The presence of branched molecules resulted in increased elasticity and slower crystallization kinetics due to higher concentration of entanglements and/or increased interchain interactions. Degradation by processing for both resins produced shorter chains, and involved reduced shear viscosity and faster crystallization kinetics, in particular, at high temperature.
Thickness Characterization of Thin Polymer Nanocomposite Oxygen Barrier
Thin films of sodium montmorrilonite clay and cationic polyacrylamide have been produced by alternately dipping a plastic substrate into dilute aqueous mixtures containing each ingredient. After 30 clay-polymer layers have been deposited, the resulting transparent films exhibit an oxygen transmission rate below the detection limit of commercial instrumentation (< 0.005 cm3/m2/day). This level of oxygen barrier, which is unprecedented for a clayfilled polymer composite, is believed to be due to a nanobrick wall microstructure comprised of completely exfoliated clay in a polymeric mortar. This brick wall creates an extremely tortuous path at thicknesses below 500 nm. Thickness measurement of these thin films is very challenging, requiring several techniques to confirm accuracy. Ellipsometry, weight measurement, and electron microscopy were used in the present study to obtain accurate thickness. With an optical transparency greater than 90% and potential for microwaveability, this thin film composite is a good candidate for foil replacement in food packaging and may be useful for flexible electronics packaging.
Polyurethanes from Soybean Oil-Based Polyols with Mixed Primary and Secondary Hydroxyls
Soybean oil was converted by epoxidation and hydroformylation to polyols with varying ratio of secondary and primary hydroxyl groups while keeping hydroxyl content approximately constant at about 200 mg KOH/g. Polyols with secondary groups were solid at room temperature. Their consistence changed gradually to liquids as the content of hydroformylated OH groups increased. Reactivity of polyols with diisocyanates was studied by viscosity increase with time. Glass transition of resulting polyurethanes with the same functionality of polyols varied linearly with the content of primary groups being lower for the higher content of hydroformylated hydroxyls. This was explained by the larger molecular weight of network chains, Mc, of hydroformylated polyols due to extra carbon atoms introduced by the process. The effect of crosslinking density, primary hydroxyl content and polyol reactivity on properties is discussed.
Investigation on Warpage and its Behavior in Sequential Overmolding
Sequential overmolding is one of the great methods to fabricate the modern injection products. Due to its complicated nature and the unclear physical mechanism, trial-and-error method can not address and manage the warpage and its mechanism effectively. In this study, various parameters including product geometrical effect and material selection have been conducted both theoretically and experimentally. Results showed that the product geometries and molded materials will affect the warpage of final products significantly. It can be the good guidelines to help people understand the mechanism and make the proper design for fabricating the modern multi-component molding products.
Analysis of Rotational Moulding Process Parameters and Warpage on Cycle Times
The analysis of heat transfer in the rotational moulding process is a non-linear multi-dimensional problem, which involves a number of process conditions and thermal parameters. This study, mostly involves dimensional analysis, the changing effects of the process parameters and conditions on the process times for different processing circumstances. The modelling helps to further identify and understand the dependence of key thermal parameters due to external heating, external cooling, external-internal cooling and warpage on cycle times of the rotational moulding. This study shows that for the external cooling process, the warpage formation for thicker parts does have a considerable influence on prolonging the total cycle time, also the external-internal cooling method significantly improves the cycle time.
A Constitutive Model for Creep Lifetime of PBO Braided Cord
A constitutive model to describe the creep lifetime of PBO braided cord has been developed and fit to laboratory data. The model follows an approach proposed for p-aramid cord in similar applications, and has an Arrhenius-type representation that arises from consideration of the failure phenomenon mechanism. The data were obtained using a hydraulic-type universal testing machine, and were analyzed according to Weibull statistics using commercially-available software. The application of concern to the author is NASA's Ultra- Long Duration Balloon and other gossamer spacecraft, but the motivations for the related p-aramid works suggest broader interest.
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