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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New Light Stabilizer for Coextruded Polycarbonate Sheet
Weatherable polycarbonate sheet can be produced by coextruding a cap layer containing a UV absorber over a minimally-stabilized bulk layer. A new UV absorber based on hydroxyphenyltriazine chemistry has been developed that is especially suited to this application. The product provides superior long term weatherability due to its strong UV absorbance and its excellent photostability. It is also relatively nonvolatile, and has only a minimal effect on melt viscosity.
Diffusion at Polymer-Polymer Interfaces Probed by ATR-Attenuated Total Reflection
In this work we report on the quantification of concentration profiles across the polystyrene-polyvinyl methyl ether interface through ATR-Attenuated total reflection technique. Different narrow molecular weight distributions and different temperatures above and below the glass transition temperature of polystyrene were tested both in the one phase and two-phase regions. The effects of temperature and molecular weight on the diffusion mechanism are discussed in terms of the phase behavior.
Determining Tear Resistance in Blown Film Using a Single Specimen J-Integral Approach
A single specimen J-integral approach is developed to determine the fracture toughness of thin polyethylene blown films. The test is used to determine the amount of energy required to initiate crack growth as well as the energy required to propagate the crack. This paper presents preliminary findings using the single specimen J-integral approach on LLDPE blown films. A comparison between J, Elmendorf, and Dart is provided.
Crack Growth Studies for Polyacetyl Resins in Chlorinated Water
The crack growth resistance in chlorinated water has been measured for two polyacetal resins of different molecular weights. The crack growth rates were measured using single edge notched tensile specimens under constant stress at elevated temperatures. The crack resistance measured in hot water containing free chlorine were found to provide a reasonable explanation for the observed poor field performance of these resins in hot water plumbing applications.
Fluorescence Anisotropy Measurements of Oriented Polymers
Fluorescence anisotropy area scans of sheet and film specimens have been carried out using a fiber optic sensor that contains polarizing optical elements. Measurements on polyethylene terephthalate food packaging, which contains the fluorescent dye benzoxazolyl stilbene, are presented. In one case, a sheet cut from the side of a blow molded bottle displayed variation in biaxial orientation as a function of distance from the neck of the bottle. In another case, a thin film of shrink wrap material showed uniform biaxial orientation over the scanned area.
A Quantitative Investigation of Mixing in a Miscible SAN/PMMA Blend
Mixing of miscible additives into polymeric matrices is being investigated using the model blend SAN/PMMA. The normalized sample variance, as measured by FT-IR, is used to quantify the extent of mixing. The graph of normalized sample variance as a function of sample size reveals that there are at least two characteristic size scales present in short-time mixing samples. Theoretical calculations support this conclusion.
Three Dimensional, Nonisothermal Analysis of RTM and VARTM Processes Using hp-Adaptive Finite Element Method
A highly accurate numerical technique for the simulation of resin infusion in composite preforms using a transient, 3-D, non-isothermal, two-phase analysis is presented. An adaptive finite element method is used to solve the equations. The uniqueness of the present approach is that resin infusion is modeled as a weakly compressible, two-phase flow in a porous media. VARTM processes can be solved by accurately specifying air properties based on the vacuum conditions. The results presented indicate the usefulness of the model.
Solvent Effects on the Mechanical Properties of Peek: An In-Situ Dynamic Mechanical Analysis Technique
Amorphous poly(ether ether ketone)(PEEK) plasticizes and/or crystallizes in the presence of common organic solvents. In-situ Dynamic Mechanical Analysis techniques have been employed to study the effects of solvent-induced crystallization on the storage modulus (stiffness) of amorphous PEEK. Preliminary results indicate that the Tg of PEEK is depressed below 20°C allowing for room temperature crystallization. Real-time immersion at room temperature shows the competing effects of plasticization and crystallization on the mechanical response of PEEK.
Cavity Pressure Studies for Stereolithography Produced Tooling
The objectives of the study are to: 1)Determine the relationship between cavity pressure and tool failure; 2)Evaluate the feasibility and effectiveness of cavity pressure transfer from first to second stage for stereolithography (SLA) produced tooling; and 3)Evaluate the effectiveness of computer simulation in determining the startup conditions for the AIM* injection molding process.
Investigation of the Reaction Kinetics within Expandable Mixtures Used for Preparing Injection-Molded Polyolefin Foams
In this study, expandable polyolefin elastomer mixtures used for preparing cross-linked polyolefin foams were studied by Differential Scanning Calorimetry (DSC) to determine the reaction rate constants for azodicarbonamide (AZDC) decomposition. Activation energies and rate constants were computed from results obtained by variable heating rate DSC experiments. Predictions made from the kinetic equations were compared with results from isothermal aging experiments as well as observations made during injection molding of cross-linked foams.
Effect of Applied External Pressure on the Surface Concentration of Erucamide in LLDPE Films
External pressure was applied to extruded LLDPE films with an average thickness of 70 microns at 35°C and 50°C for prescribed periods of time. The final surface concentration of the slip agent (erucamide) was then compared to the initial concentration. Three applied pressures were used and diffusion profiles were determined using FTIR-ATR spectroscopy.
Experimental Comparison of Floating Ring Mixing Devices
Experiments were performed to determine the performance of three floating ring mixing devices. The mixers studied were 1) a Twente mixing ring, 2) a Barr sleeve mixer, and 3) a Barr ring mixer. Performance was measured using extrudate sampling, extruder performance, and extrusion solidification experiments.
An Optical Determination of Melt Viscosity through Particle Kinematics
Melt viscosity is calculated by observing contaminant flow in a low density polyethylene melt stream. The melt stream is radiated by visible light and images of flowing particles are captured and processed. Particle flow rates are measured across the stream, and a velocity profile is then determined. Viscosity is calculated from this profile.
Studies of Sharkskin Melt Fracture Using a Model Polymer
Sharkskin melt fracture (SSMF) of, especially, LLDPE has been studied for several decades because of its economic importance and scientific interest. SSMF occurs on extrusion of some--but not all--polymer melts; examples include LLDPE, PDMS and polybutadiene (PBD). PBD exhibits remarkably similar flow and SSMF behavior to LLDPE, but is easier to work with. Evidence for the origin of SSMF inside the die was sought, but not found, leaving the exit as the probable source of SSMF for this resin.
Effect of Metallocene Polyethylene on Heat Sealing Properties of Low Density Polyethylene Blends
Laminations made with blends of metallocene Polyethylene (m-PE) and high-pressure low density Polyethylene (LDPE) were prepared to investigate the effect of the former resin on heat sealing performance. According to various experimental studies of seal strength, hot tack and differential scanning calorimeter (DSC), it could be concluded that percentages around 15% of m-PE allow to obtain the optimal balance for heat sealing properties and cost. Using the interdiffusion theory of heat sealing, a thorough discussion of the results was done.
The Color Image Coding Analysis of Progressively Degrading Polymers
Many an industrial polymer product reveals, once its quality diverts from set standards, either a change in color or an increase in fluorescence. After their accelerated ageing, various products are scanned on special flatbed scanners and their filed images are then color coded to determine with high accuracy their color composition, fluorescence intensity and the extent of their discoloration during processing.
The Effect of Salt Absorption on Nylon
One of the most common environmental exposures that nylon undergoes when used for automotive applications is that of salt splash, which commonly occurs during winter driving. This study looks at the effect of various salts (NaCl, KCl, CaCl2) on the mechanical and thermal properties of nylon when exposed to one and four molar aqueous salt solutions. Also, the partition of the salt/water solutions was studied, as well as the preferential absorption of one salt over another.
Comparison of the Morphologies of Hot-Tool and Vibration Welds of Thermoplastics
Because the heating rates in hot-tool and vibration welding are very different, and the higher weld pressures used in vibration welding induce more squeeze flow, the weld zones in these two processes see very different flows and cooling rates, resulting in different morphologies. The weld morphologies of bisphenol-A polycarbonate and poly(butylene terephthalate) for these two processes are discussed in relation to these differences.
Injection Mold's Problems Solved by CAE Analysis
The use of CAE1 as a powerful tool to analyze injection mold quality has given encouraging results. CAE is used to deal with mold troubleshooting and to solve problems concerning Filling Time, Injection Pressure, Gate Position and Dimensions, Warpage, Coolant Efficiency, etc. This paper focuses some of these parameters to its weightiness for Mold Technologies Division. Therefore CAE is a powerful tool to assure quality, price and time delivery.
Effect of Pressure on Crystallization of Polyethylene
The morphology and crystallinity of plastics articles are influenced by several parameters, in particular the pressure and the temperature history during solidification. In this study, the crystallization kinetics and the PVT behavior of a high-density and linear low-density polyethylene resins were evaluated and compared using a high-pressure dilatometer under both isothermal and isobaric conditions. Also, the PVT behavior was compared to the predictions of the Tait equation of state. It was found that the induction time increases with increasing pressure, suggesting that pressure delays crystallization.
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