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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Diverse Morphologies and Dynamic Mechanical Behavior in Metallocene Polyethylene Copolymers
Dynamic mechanical relaxation experiments were performed on a series of ethylene/1-octene copolymers with diverse morphologies from impinged spherulite to totally amorphous structure. The continuously changing dynamic mechanical relaxation behavior is related to structure parameters, such as crystal structure, crystallinity and lamellar thickness, acquired from DSC, WAXD, and SAXS experiments.
Polymer Blends as Proton-Exchange Membrane Materials for Fuel Cells
Blends of sulfonated poly(ether ketone ketone) (SPEKK) and poly(ether imide) (PEI) are being considered as proton-exchange membranes (PEMs) to achieve high conductivities while maintaining the mechanical stability required for use in fuel cells. Proton conductivity comparable to Nafion™ has been obtained. Variables such as the SPEKK sulfonation level, the blend composition and the membrane casting procedure affect the blend microstructure and the fuel cell performance.
Effect of the Viscosity Ratio on the Particle Coalescence in PS/HDPE Blends under Extensional Flow
The effect of viscosity ratio and concentration on particle coalescence in PS/HDPE blends was studied. Three different PS and HDPE were used in order to modify the viscosity ratio (p). The blends were prepared by extrusion at 200°C. A morphological study in postextrusion zone is presented where the draw-down ratio (DR) is varied. The evolution of particle to fibers is interpreted in terms of coalescence particles where the viscosity ratio plays an important role.
Modeling of Cell Structure in Polyurethane Foam
We suggested that the cell structure of polyurethane foam could be approximated to be oval by the use of Finite Element Method. Three kinds of parameters for cell modeling were employed, which are ratio of radius, the area, and thickness of cell wall.
Enhancement of Adhesion between High Density Polyethylene and Poly (Ethylene Terephthalate) Films
Blends of high density polyethylene (HDPE) and ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) prepared in a twin-screw extruder, were used to improve the adhesion between HDPE and poly(ethylene terephthalate), PET films.The results of T-peel tests showed that the adhesion strength between the films increased with increasing bonding temperature, pressing time and elastomer concentration. The adhesion characteristics of multilayer films were studied in terms of morphological and spectroscopic analyses.
Comparing Models for the Glass Transition Temperatures of Compatible Polymer Mixtures
Various proposed equations relating glass transition temperature to composition are compared for:. Relative success in fitting unsymmetrical temperature-composition diagrams,. Number (and ease of establishing) required constants, and, Ability to be cast explicitly in either temperature or composition. A novel exponential form satisfies these criteria very well. It is contrasted with another author's equally successful but mechanically awkward form which is based on thermodynamic considerations
Break-Through in High Performance Ionomers: Morphology and Properties
Ethylene ionomers have been the material of choice for the golf ball cover and mantle applications due to the excellent resilience, high cut resistance, and good impact durability. The ethylene ionomers achieve the unique property characteristics through the development of network morphology. In this paper we discuss the development of ionomers with novel compositions, we present evidence of the effect of composition on morphology, and propose a model that accounts for the outstanding performance of these ionomers.
Characterization of LLDPE/Monmorillonite Nanocomposite
Physical properties, such as gas permeability, tensile property, and dispersion behavior of nanopowder of linear low density polyethylene and monmorillonite nanocomposite were investigated. Nanocomposites were prepared by twin screw extruder and internal mixer under various processing conditions. XRD was used to evaluate the degree of intercalation/exfoliation. Significant change of dispersion behavior of monmorillonite and physical properties were observed depending on the processing conditions
Mechanical Behavior of Thermoplastic Olefins (TPOs) during Three-Point Bend Impact
We have characterized the mechanical behavior of five commercially available thermoplastic olefins (TPOs) and a polypropylene homopolymer (PP) during quasi-static (1.7 x 10-5 m/s) and dynamic (2.2 and 8.9 m/s) three-point bend loading at -40, -30 and 22 °C. All materials tested stiffened significantly with increasing impact speed and decreasing temperatures. Flexural moduli increased 51 to 119 % with increasing impact speeds, while increases of 86 to 219 % were measured during low temperature tests.
Relation between Mobility and Diffusion Factors for Thermoset Cure
The temperature-modulated differential scanning calorimetry (TMDSC) response during cure of thermosetting materials is modeled using chemical reaction kinetics with diffusion control. Physical aging effects are incorporated into the model using the Tool-Narayanaswamy-Moynihan equations. We investigate the assumption that the mobility factor, which is often obtained from experimental TMDSC reversing heat flow data, is related to the diffusion factor.
Effect of Cure Cycle on Residual Stress Development in Thermosetting Materials
We have studied the effect of cure cycle on isotropic residual stress development stress development in thermosetting resins during cure and subsequent thermal cycling. We use a thick-walled tube to impose three-dimensional isotropic constraints on the resin. The strain at the outer surface of the load cell is monitored by strain gauges. Cure-induced stresses are much lower than expected from cure shrinkage due to the inability of the curing resin to sustain large tensile stresses in the rubbery state.
Effects of Ultrasonic Processing on the Thermal Behavior of Epoxy Polymers
Ultrasonic cavitation shows great promise in the development and fabrication of polymer composites, including nanocomposites. We report how the ultrasonic processing of two epoxies affected their curing behavior by undertaking systematic differential scanning calorimetry (DSC) and transmission-Fourier transform infrared (FTIR) measurements.
The Effect of Atmospheric Pressure Glow Discharge (APGD) Treatment on Polyetherimide, Polybutyleneterephthalate and Polyamides
In this work, polyamide, polyamide, polybutyleneterephthalate and polyetherimide films were treated in an APGD unit using various applied voltages, frequencies and dwell times. The results show changes in the surface chemistry (FTIR); the degree of change in dynamic contact angle was found to be dependent on the polymer type, dwell time and electrical characteristics of the plasma.
Evaluation of a Molecular-Based Yield Model for Glassy Networks
Results are presented from an experimental investigation to evaluate the validity of a new, molecular based yield model. The proposed model incorporates effects of test conditions such as stress state, strain rate and temperature, as well as the effects of molecular architecture. The effects of molecular architecture are quantified by parameters considering stiffness and cohesive strength of the network. Previously published data along with new results of yield in compression and plane strain are used to assess the validity of the proposed model.
Performance Comparison of a Custom Strain Gage Based Load Cell with a Rheometric Series Force Rebalance Transducer
Normal force measurement issues and the fragile nature of the 2K FRT are major problems with the current ARES Rheometer system. In an attempt to overcome these two issues a custom designed semiconductor strain gage based transducer was successfully installed in an ARES Rheometer. A comparison of the performance of a Rheometric Scientific series 2K FRT and the strain gage based transducer was performed. A comparison of sensitivity, accuracy and drift of data is shown for these two transducers.
High Tg Polymer/Electroactive Organic Compound Blends for LED/PV Applications
The utilization of high Tg polymers to sequester low molecular weight electroactive organic compounds in the active layers of light emitting diode and photovoltaic devices has been demonstrated. The high Tg polymer allows for increasing the layer Tg, decreasing the crystallization rate, improving the mechanical properties and offering the capability of employing low cost fabrication processes. LED and PV device data demonstrating the concept will be presented.
Understanding and Control of Sharkskin
The sharkskin instability remains an unsolved problem in extrusion because the exit singularity induces a complex set of interactions that leads to the rough surface. We review the significant progress over the past decade, focusing on the elucidation of the flow and stress fields at the die exit. We review two critical areas; first an elucidation of the nature of the flow boundary condition for the polymer near the wall at the exit; in particular the question of whether there is a stick or slip boundary condition. Second, we discuss the reasons for the elimination of the instability upon changing the boundary condition to that of slip.
Fabrication and Characterization of Structure Membranes for Proton Transport
Polymer blend technology was used to create highly anisotropic membranes for fuel cell applications. An important factor for creating structures of high proton conductivity and low methanol permeability was the application of electric fields of selected magnitude and frequency during the formation of the membrane.
Thermal and Electrical Analysis of Vapor Grown Carbon Nanofiber/Polyoxymethylene (VGCNF/POM) Composites
Vapor grown carbon nanofiber (VGCNF) reinforced polyoxymethylene (POM) composites were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The electrical resistivity was also analyzed. The thermal stability of the composites was affected by VGCNFs. A drop of 14 orders of magnitude of volume resistivity was obtained by inclusion of 5 wt% VGCNFs. VGCNFs were shown to act as defects, the crystallinity was lowered and the crystallization was delayed.
Smart Adhesion: Controlling Polymer Interfaces through Patterning
To understand the role of patterned geometries/topographies in controlling polymer adhesion and release, we fabricate controlled structures ranging from the nanometer to micron length scales on polymer surfaces. Our initial results focus on the effect of patterned arrays of micron-scale posts and holes on the adhesion of polydimethylsiloxane layers. To facilitate the exploration of the large, possibly non-continuous parameter space presented by this problem, we rely upon combinatorial methodologies to effectively screen multiparameter maps.
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