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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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.
The Reinforcement of Poly(Lactic Acid) Using High Aspect Ratio Calcium Carbonate Based Mineral Additive
As a sustainable alternative to petrochemical-derived products, poly(lactic acid) (PLA) is gaining a lot of interest in recent years. PLA has good optical clarity and high stiffness, but it is also intrinsically brittle. In this paper, the comparison between a specially engineered high aspect ratio mineral-EMforceTM Bio calcium carbonate, mica and talc in reinforcing PLA was performed. It was found that EMforceTM Bio calcium carbonate was extremely effective in improving the low temperature impact toughness as well as increasing the stiffness of PLA. Further the addition of EMforceTM Bio calcium carbonate to PLA does not hinder its compostability at elevated temperatures.
Insert Coating as a Pre-Processing Approach for Improvement of Adhesive Bonding in Plastic-Metal Hybrid Structures
Improvement of adhesive bonding between plastic and metal components by means of surface coating pretreatment has been investigated. Metal inserts have been coated with polymer-based film then overmolded with reinforced polyamide-6 in an injection molding process. Experimental work has included the characterization of the adhesive bonding strength and the influence of the coating film on the mechanical behavior. FE-Simulation has been conducted to analyze the local shear stresses. Aging influence has been evaluated using climate change test.
ION/Polymer Interactions in Polyelectrolyte Gels
We report results from experimental studies performed on polyelectrolyte gels to understand the volume transition induced by multivalent cations. Macroscopic osmotic and mechanical measurements are made to determine the effect of ion binding on the elastic and mixing contributions of the network free energy. Small-angle neutron scattering is used to reveal the role of multivalent ions in the organization of the polymer segments. We demonstrate that combination of scattering and osmotic measurements allows us to determine the characteristic size of the structural elements that contribute to the osmotically driven concentration fluctuations, and yields important information on the effect of ions on the structure and thermodynamic properties at both molecular and supermolecular levels.
Effect of Strain Rate on Tensile Properties of Carbon Nanofiber-Reinforced SC-15 Epoxy
In this study, tensile tests were performed on carbon nanofiber reinforced epoxy at different strain rates. Tests results showed that both the elastic modulus and the tensile strength of the materials increased with higher strain rates, but the failure strain decreased with higher strain rates, indicating that the composite is a strain rate-dependent material. Experiment results also showed an even distribution of CNFs in the 1 wt% and 2 wt% systems and an agglomeration of CNFs in the 3 wt% system. Therefore, the 2 wt% CNF-infusion system exhibited maximum enhancement, compared to other systems.
Clear Barrier at Atmospheric Pressure – the Second Phase
The barrier properties of transparent layers deposited on flexible plastic substrates are of interest to many in the packaging industry. Numerous methods have been used to manufacture transparent barrier coatings with varying degrees of success to address evolving environmental laws requiring the reduction or elimination of volatile organic compounds (VOCs), which are the byproduct of curing liquid topcoats. There is also a consumer preference to visually inspect packaged products through packaging prior to purchase. This paper will present new evidence since the 2006 SPE FlexPack Conference of the potential for clear barrier at atmospheric pressure through the use of plasma processing as integral steps in a composite, or several stage, process for deposition and polymerization of functional barrier coatings. XPS analysis of polymerized film showed presence of silicon, carbon and oxygen in ratios different from the monomer, and in fact approaching a Si:O atomic ratio of 1:2 confirming cross linking effects, and the plasma polymerized organo-silicon films displayed good functional barrier properties without the environmental concerns of VOCs.
Mini Mixing Devices for Specialty Nano-Strucured Blends and Composites: Evaluation of Flow, Mixing and Morphology
A 1:20 downscale of an internal batch mixer (60mL total volume), the Minibatch mixer (3 mL total volume), requiring only 2g per blend sample, has been developed for small-scale blending of specialty polymers and nanocomposites. The morphology of samples processed by this new miniature mixer is compared to other labscale equipment such as the 60mL internal batch mixer and the Alberta Polymer Asymmetric Minimixer (APAM). Immiscible blends showed a spherical dispersed phase structure and uniform distribution throughout the blend; however, the dispersed phase particle size was large in comparison to the other mixers. Vapor grown carbon fiber (VGCF) nanocomposites were better dispersed and more homogeneous compared to those prepared using the 60mL batch mixer and the APAM. The large surface to volume ratio of this new mixer plays an important role in the heat transfer mechanisms and thus may affect flow patterns occurring in the Minibatch mixer. Simulations using Polyflow software showed that the flow pattern in the 3mL Minibatch is similar to the 60mL batch mixer but that the temperature rise due to viscous dissipation is not as large for the new miniature mixer.
Comparison between Amorphous Metallic Alloy and Silicon as Molding Insert for Micro Injection Molding of Polymers
The mass-production of microfluidic devices must be done in a reliable manner. In this study, toolings used to reproduce microfluidic features on cyclic-olefincopolymer (COC) and polymethyl-methacrylate (PMMA) polymers by amorphous metallic alloy and silicon inserts were compared. Both toolings were used in micro injection molding. Findings indicate that the alloy was mechanically more suitable as mold inserts, whereas silicon had better surface roughness. COC samples showed comparable geometrical replication of microfluidic features compared to PMMA.
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