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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Crack Propagation in Continuous Glass Fiber/Polypropylene Composites: Matrix Microstructure Effect
The crack propagation behavior of a unidirectional continuous glass fiber/polypropylene (GF/PP) composite with two different matrix morphologies was studied. Changes in the matrix morphology obtained by varying the cooling rates during the molding process resulted in changes in: 1) the flexural strength and strain at failure using three-point bending specimens; 2) the critical strain energy release rate in mode I quasi-static crack growth using double-cantilever beam (DBC) specimens; 3) the fatigue crack growth rates at given levels of strain energy release rate in mode II fatigue crack propagation using end-notch flexure (ENF) specimens. The reduced presence of the ductile amorphous PP phase in the PP/GF composite at lower cooling rates is responsible for the reduction in mechanical performance.
A Gram of Prevention: Additives to Improve UV Stability and Processability of Rotomolded Parts
As the size of the rotomolding market increases, so do customers expectations for a longer service life and alternative resins. Small amounts of UV stabilizers and antioxidants can greatly improve the service life of a molded part as well as address some of the special challenges present in the rotomolding industry today. This paper will address the current issues in rotomolding and how UV and AO technology can be used to provide protection to the molded part.
Stabilization of TPE's
A rational approach to the stabilization of thermoplastic elastomers (TPE's) is an extension of the known technology to stabilize the constituent polymer resins. Hindered amine light stabilizers and ultraviolet light absorbers are effective in polypropylene and polyethylene. They can also be used to stabilize multiphase TPE's, based on polyolefin copolymers, against the effects of long term exposure to light and heat.
Epoxy + Montmorillonite Nanocomposite: Effect of Composition on the Catalyzed Reaction Rate
Differential scanning Calorimetry was used to determine the effect of incremental change in composition of alkonium ion substituted montmorillonite clay dispersed in thermoset epoxy with a simple diamine hardener. Catalytic effects due the reactivity of the reinforcement are shown to be variable with composition. Infra-red analysis of the epoxy monomer indicate a change in the morphology of the molecular reinforcement may alter the ability of the reactants to come into contact even before the chemical reaction has begun.
Simple and Concise Design Rules for Rapid Prototyping
Shortening the design cycle by using rapid prototyping is a standard for injection molding product creation throughout the world. Developing new products while being aware of each type of prototyping technology allows the designer to judge fit, function, esthetics, economics, and product features prior to cutting a production tool; saving money and time. The use of several prototyping processes, including stereolithography (SLA) and laser sintering (SLS) are detailed with updated information on new tolerance standards and new materials.
Spectroscopic Studies of Ion Implanted Polycarbonate
Ion implantation is a process by which ions are accelerated and focused at a rapid speed to a target at energies high enough to bury them just below the target's surface. These ions penetrate the sample surface and form a thin layer below the surface. Until recently this technique was mainly utilized for modification of semiconductors (1) or to improve wear characteristics in metal tooling and polymers (2,3). Now the use of ion implantation has been extended to polymers. Improvements in adhesion (4), electrical (5) and abrasion (6) have been reported. The resulting chemical effect of ion implantation in polymer systems is to increase chain scission and cross-linking., while decreasing crystallinity(7). In this study, the effects of medium energy ion implantation of boron, nitrogen and fluorine into a polycarbonate matrix was examined by Fourier transform infrared spectroscopy and UV/VIS spectroscopy. The implanted polycarbonate linkage degrades upon implantation. Further implantation leads to carbonization just below the surface of the specimens.
Optimization of Composition of Soy-Based Polyols for Rigid Polyurethane Foams
Soybean oil-based polyols can be synthesized with different OH content. Higher OH number polyols display higher viscosity, which may limit their applications in foams. Adding glycerin to a polyol affects crosslinking density and homogeneity of the networks. It would be advantageous to use a lower OH content and a lower viscosity polyol and adjust the OH number with glycerin if the properties would stay the same. Apart from having lower viscosity, polyols with lower a OH number are easier to prepare. It has been shown that rigid foams based on the polyol having an OH number of 180 mg KOH/g have similar properties as those based on the polyol with an OH number of 208 mg KOH/g if the final OH number of the polyol system (polyol, crosslinker and water) is adjusted to the same value, although heat stability (onset of softening) of the former was lower.
Processing and Properties of Polymer Nano-Composites
Polymer nano-composites are prepared by melt intercalation in this study. Nano-clay is mixed with either a polymer or polymer blends by twin screw extrusion. The clay-spacing in the composites is measured by X-ray Diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by SEM. Rheological behavior of the composites are measured. It is found that the clay spacing and composite morphology are influenced by the concentration of the nano-clay and the type of polymer used. The addition of the nano-clay can greatly increase the viscosity of the polymer when there is strong interaction. If such polymer/nano-clay mixture is used as the matrix phase, it would lead to improved dispersion and distribution of the minor phase in the polymer blends. The effect of nano-clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.
Effects of Impact Modifiers on the Properties of Rigid PVC/Wood-Fiber Composites
This study examined the effects of impact modifier types and addition levels on the mechanical properties of rigid PVC/wood-fiber composites. The formulations of the composites were modified by incorporating crosslinked (all acrylic and methacrylate butadiene styrene) and uncrosslinked (chlorinated polyethylene) impact modifiers at various concentrations. Mixtures of PVC, wood-fibers, impact modifiers, and other processing additives were dry-blended using a high-intensity mixer. The dry-blended compounds were extruded, compression molded, and tested for tensile and Izod impact strength properties. Analysis of variance (ANOVA) was used to discern the effects of impact modification on the mechanical properties of the composites. The experimental results indicated that the impact resistance of rigid PVC/wood-fiber composites depends strongly on the type and content of impact modifier. With the proper choice of modifier type and concentration, the impact strength of rigid PVC/wood fiber composites can be significantly improved without degrading the tensile properties. Methacrylate butadiene styrene and all acrylic modifiers performed in a similar manner and were more effective in improving the impact resistance of rigid PVC/wood-fiber composites than the chlorinated polyethylene modifier.
A Practical Fiber Optic Sensor to Monitor Resin Cure and Interphase Formation
A fluorescent probe, covalently grafted to glass, is used to study the glass / resin interphase region near the surface. A shift in the fluorescence maximum during resin cure can be monitored when the grafted dye is immersed in epoxy. The position of the fluorescence maximum is used to detect a difference between the bulk resin and interphase. To make the technique practical as a cure sensor, the dye can be grafted to a glass fiber optic.
Structural Order and Charge Transport in Polymers
It has long been known that polymers have a structural order intermediate between that of insulators and that of amorphous materials. We show how this intermediate type of order leads to anomalous charge conduction properties for insulating, semiconducting, and metallic polymers. Concepts such as fractal dimensionality and mesoscopic order are introduced and their unusual predictions for variation of conductivity and dielectric constant with temperature and frequency are presented. A comparison with experimental results for undoped and doped polymers is presented.
An Analysis of the Heat Exchange Phenomena in Heavy Gauge Thermoforming-Part I
A comprehensive analysis of the heat exchanges between an instrumented Aluminum mold and various thermoforming materials were made during controlled heavy gauge production trials. Five materials Impact Polystyrene, High Density Polyethylene, PETG, ABS and Impact Polypropylene Copolymer were evaluated. Heat flux was calculated. Experimental variables were quiescent and circulated ambient air, mold and coolant temperatures.
Predicting Thermal Degradation of PVC Compounds during Injection Molding
The goal of this study was to determine the degree of degradation during PVC injection molding and to compare the results with a computational model. It was found that a good agreement between experimental and computational results was obtained only if the reaction was assumed to be more thermally sensitive than found in literature. The results from this study show that during injection the activation energy for degradation was 65 kcal/mol, compared to 17-30 kcal/mol found in literature for quiescent systems.
The Effect of Tie-Layers on Optical Properties of Coextruded Multilayer Films
The tie-layer is a critical component of multilayer films and can effect the optical properties of the overall film structure. This paper evaluates various tie-layers for their effect on optical properties of the film. The see-through and contact clarity of the film is explained based on a combination of the physical properties of the tie-layer resin and the effect of the interfacial region on flow instability. Rheology of the interfacial region is discussed based on controlled experiments simulating the reaction that occurs during multilayer extrusion and shows that the shear stress and complex viscosity can be used to estimate the see-through clarity in multilayer coextruded films.
Optimizing the High Speed Machining Process for Hardened Steel Molds
Constantly reduced product life cycles and increasing product variety compels the moldmaker to cut down on long production times especially in mold and die making. Electrical Discharge Machining (EDM) has been the conventional finishing technique for generating complex free form surfaces. However, the EDM process also generates a brittle, recast layer, which is often detrimental to mold performance. High speed machining technology of today offers an economical alternative to EDM, which does not significantly deteriorate mold surface properties. This paper will evaluate the benefits of a high-speed machined mold compared with conventional manufacturing techniques. It will also investigate the effects of different cutting parameters, in an attempt to optimize the high speed machining process.
Flow Behavior of Sparsely Branched Metallocene-Catalyzed Polyethylenes
The dramatic effect of chain architecture on the melt flow behavior of polyethylenes is well established. The advent of metallocene and other constrained-geometry catalysts now allows the precise control of molecular weight, branch content, and branch distribution. In the present study, the rheological responses of three different metallocene-catalyzed polyethylenes are analyzed. Despite similarities in their shear properties, the differences in transient extensional viscosities can be attributed to the presence of sparse long-chain branches and/or high molecular weight fractions. Melt fracture observations as well as full-field flow birefringence measurements are collected to further corroborate this idea.
Plastics Failure Due to Oxidative Degradation in Processing and Service
Aliphatic hydrocarbon polymers, such as PE, PP and copolymers thereof are particularly susceptible to oxidative degradation to lower molecular weight in processing and in service. The result is reduced strength, embrittlement, and shorter service life. High temperature required for melt processing is a major factor in oxidative degradation. Decrease in oxidative induction time or induction temperature measured by differential scanning calorimetry are practical methods of monitoring the effect. Formulations need sufficient antioxidant to be protected during processing and in service.
Nanocomposites: The Importance of Processing
Nanocomposites have been studied for nearly 50 years, but few references deal with the importance of how the organoclay was processed into the plastic of choice. Many articles focus on the importance of the chemistry used to modify the surface of the clay, usually montmorillonite, without including the role of processing. This paper demonstrates the importance of both the chemistry of the clay surface and how the clay was processed into the thermoplastic. Two different clay treatments were added to polyamide 6 using four different types of extruders with multiple screw designs.
Injection Molding and Physical Aging Properties of Amorphous Poly(ethylene terephthalate)
Physical aging characteristics of amorphous poly(ethylene terephthalate) have been evaluated in relationship to several important injection molding parameters. For these investigations; packing pressure, melt temperature, and mold temperature were each varied individually, with other conditions held constant. Aging studies were performed at three different storage temperatures, using the molded specimens. Changes in density, notched Izod impact strength, and enthalpy of relaxation were monitored as functions of aging times. Time temperature superposition analyses were performed using experimental data and master curves were constructed. Results give predictions of lower temperature long term enthalpies of relaxation and notched Izod impact strength properties.
3-D Simulation of Thin-Wall Injection Molded Part by CAE
This work reports the results of CAE simulation of thin-wall injection molded part by 3D TIMON. The model used in this simulation was a speaker grille that has thin wall and many tiny openings (net) for sound through them. These openings cause unfavorable weld lines. Effects on weld lines and effects of the number and location of gates were discussed.
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