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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Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Prediction of Long-Term Creep Behavior of Epoxy Adhesives for Aluminum Substrates
Epoxy-based adhesives for bonding aluminum substrates have gathered significant interest in recent years. Yet, more work is needed to learn how epoxy adhesives withstand creep and exposure to various environmental conditions. In this study, both experimental and modeling work (using Ngai's Coupling) has been conducted to predict creep behavior of epoxy adhesives under moisture exposure.
Prediction of Mechanical Properties of Injection Molded Plastics Components – A Systems Approach
Research objective is to establish manufacturing-related design rules and procedures for engineering design of injection molded thermoplastics parts, and to investigate application of novel materials to support development of design for sustainability. Thorough analysis of a large number of mechanical test results has led to a better understanding of factors influencing mechanical performance in tensile and tensile-impact. Among the noteworthy conclusions is the importance of shear rates and temperature gradients in the surface layers during molding.
Processability Studies on Polycaprolactone and Polybutylene Succinate Foams
Two commercial biodegradable polymers, polycaprolactone and polybutylene succinate, were used to study their processability in crosslinked foam processes. Benzoyl peroxide and t-butyl perbenzoate were used, respectively, to initiate crosslinking reactions. Zinc diacrylate was used to enhance the gel content of the crosslinked polymers. The change in melt strength of both polymer systems was assessed by measuring their dynamic mechanical properties. The effects of crosslinking agents and coagents on foam densities and gel contents are also reported.
Educating Industrial Design Engineers in Failure Awareness
Industrial designers have problems imagining how their designed plastic products might fail.The paper illustrates how our students are educated about the specific structure related properties that might cause failures.A specific course about designing for reliability of plastic products is outlined. Case studies showing failed products are important.Students must be aware of failure causes like: stress concentrations, low mass and/or mould temperatures, highly stressed weld lines, faulty ribbing and incorrect joining.The course deals also with typical failure mechanisms of plastics like: creep and stress relaxation, stable crack extension, chemical attack and environmental stress - cracking.
Effect of Additives on the Solubility and Diffusivity of CO2 in Polystyrene
Carbon dioxide is widely recognized as an environmental-friendly blowing agent for foam extrusion. However, it is also more difficult to process than other gases because of its low solubility and high diffusivity. In order to improve processing, it might be suitable to use additives. The aim of this work was to study the effect of such additives on the solubility and diffusivity of carbon dioxide in the solid state and to validate their effectiveness in a foam extrusion process.Three “CO2-philic” additives were added to polystyrene and sorption experiments were conducted to measure the solubility and diffusivity at room temperature. Results show that all three additives had a small but measurable effect on gas solubility, which was a consequence of the free volume increase in the polymer blend and in some cases, due to the specific interaction of carbon dioxide with the compounds. Diffusion was also affected depending on the concentration of additive.
Effect of an Environmental Stress Cracking Agent on Slow Crack Propagation of Polyethylene
The effect of an environmental stress cracking agent on slow crack propagation in creep and fatigue of polyethylene resins was studied. At 50°C, fatigue and creep behavior of polyethylene in Igepal solutions followed the same stepwise mechanism as in air. The fatigue to creep correlation was probed by increasing Rratio (defined as the ratio of minimum to maximum stress in the fatigue loading cycle) from 0.1 to 1.0. Unexpectedly, 10% Igepal CO-630 solution, an ASTM standard environmental stress cracking agent, retarded fatigue crack propagation at R-ratio 0.1 but accelerated crack propagation at increasing R-ratios, in comparison with experiments in air. In contrast, fatigue and creep experiments in another longer chain Igepal solution, Igepal CO-997, showed no appreciable effect on crack propagation kinetics at different R-ratio compared to air.
Recycling Thermoset Plastics, Can it be Done?
This paper addresses the possibility of using recycled thermoset plastic powder as filler. With budget issues in the academic setting, using recycled thermoset powder as filler could have a positive impact. Recycled powder has been successfully used in a university plastics lab for rotational molding, thermoforming molds, and for composite tooling dough. Three practical lab exercises will be given in the paper.
Effect of Heat-Sealing Temperature on Mechanical Properties at Heat-Sealed Parts in Biodegradable Plastic Film
The heat-sealing machine is a vital tool in plastic bag manufacture. Processing conditions such as heat-sealing temperature and pressure greatly affect mechanical properties of the heat sealed part. In this study, the mechanical properties of the heat sealed part of a biodegradable plastic film were examined. Based on the results obtained from peeling test, circular notch tensile test and DSC measurement, the optimum heat sealing was established at 130-135 °C. The mechanical properties of the heat seals decreased with increasing heat sealing temperature.
Reliability of Joining Plastic Parts
Critical items in designs of plastic products are joints. The paper will deal with a number of design aspects about designing reliable plastic products. It will combine the results from our research in the field of stress concentrations, orientation and weld lines around holes, embrittlement of polymers, adhesion and environmental stress corrosion. A number of failures in practice will be presented.
Effect of Processing Conditions on the Physico-Mechanical Properties of Cellulose Fiber Reinforced Poly (Lactic Acid)
Green composites were made from poly (lactic acid) (PLA) and cellulose fibers by extrusion followed by injection molding processing and their physico-mechanical properties were evaluated. The properties of PLA reinforced with varying amounts of wood pulp-based cellulose materials were studied. These composites possess superior thermal and mechanical properties based on the strong interaction between the PLA matrix and the cellulose fibers. It was found that the wood pulp-based cellulose fiber could be a good reinforcement candidate for the high performance biodegradable polymer composites.
Sequential Mixing Methods of Environmentally Benign Nanocomposites from Cellulose Acetate/Plasticizer/Organoclay System
Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), triethyl citrate (TEC) plasticizer and organically modified clay. The effect of sequential mixing methods and plasticizing conditions on the performance of these nanocomposites has been evaluated. The mechanical and thermal properties of nanocomposites are correlated with the XRD and TEM observations. Cellulosic plastic-based nanocomposites with 75-minute pre-prasticized CA/TEC/organoclay showed the best exfoliated structure.
Study of the Processability of Post-Consumer and Post-Industrial Recycled High-Impact Polystyrene
In this work, the process of recycling high-impact polystyrene, both post-consumer and post-industrial, was studied. Blends of recycled/virgin materials were made and their MFI, mechanical properties and processability (thermoforming) were evaluated. Few differences in the behavior of the materials were found and their use as thermoformed packaging was ascertained.
Elastomeric Property Characterization of Thermoplastic Elastomers
The elastomeric properties of polyolefin thermoplastic vulcanizates (TPV) have been characterized by compression set, recoverable strain after hysteresis, and thermal scanning stress relaxation (TSSR) analysis. Unlike a thermoset rubber, a TPV is a two-phase system with highly crosslinked fine rubber particles dispersed in a thermoplastic matrix. Compression set, which was originally designed to characterize the elastomeric properties of a thermoset rubber, does not truly characterize the unique elastomeric properties for a TPV. Compression set for a TPV is not only highly dependent on the crosslinking density and structure, but also very sensitive to the orientation of the two phases in the TPV. For the same TPV with a fully crosslinked rubber phase, the compression set value can vary substantially depending on sample preparation and thermal history. Elastomeric properties can be better characterized by the recoverable strain after hysteresis and TSSR stress-temperature curve. The thermal-mechanical properties or stress relaxation behaviors provides more useful information for designing and producing all-thermoplastic parts, such as automotive seals, from TPV.
Enhancement of Poly (L-Lactide) Properties through Nanocomposite Formation
Nanocomposites are materials that exhibit a change in composition and structure over a nanometer length scale. In many cases, these systems have shown remarkable property enhancements compared to traditional polymers. Recently, poly (L-lactide) (PLLA) has received considerable attention because of its “green” nature. However, the end-use properties of this biodegradable polymer typically fall short of typical petroleum based polymers. Therefore, PLLA/montmorrilonite nanocomposites have been prepared via solution blending in an attempt to enhance the properties of PLLA.
Environmental Factors in Performance Forecasting of Plastic Piping Materials
Environmental factors are known to significantly impact the oxidative failure mechanism of materials. For example, the chlorine present in potable water as a disinfectant is an oxidant that has been reported to impact the failure mechanism of materials in potable water applications. In this paper, the relationship between various potable water qualities, with different oxidative potentials, and chlorine induced oxidative failures of plastic piping materials is examined. The primary factors of potable water quality affecting oxidative strength are reviewed. Laboratory exposed pipe samples tested at various water qualities to ultimate failure are examined to determine the impact of water quality on the failure mode. The chlorine in potable water is seen to attack the inner pipe wall causing oxidation and degradation of this inner surface. The stresses on the inner wall lead to micro-crack formation in this degraded layer. These micro-cracks are seen to propagate radially through the pipe wall resulting in a brittle slit type failure. The failure mode is shown to be the same over a range of water qualities. The impact of chlorine is shown to be simply one of oxidation with the rate of degradation primarily related to the oxidative strength of the potable water. For the PEX pipe material examined, it is projected that material performance can significantly exceed the excellent performance predicted based on testing at the aggressive water qualities typically employed in validation testing, depending on the specific water quality of the end use application.
The Craze/Yield Ratio as a Measure of Polymer Toughness
The ratio of a polymer's craze strength to its yield strength is an excellent measure of toughness. It can be used to quantitatively compare materials and to predict how the ductile-brittle transition will change as a function of a variety of environmental and material variables.
The Design of the Small Punch Test and its Application to Testing Medical Polymers
The small punch test is a useful technique in the mechanical testing of polymers where limited material is available. This investigation focuses on the latest developments in the small punch test design, including integrated temperature control and environmental conditioning and its use in analysis of polymethyl methacrylate (PMMA) bone cement.
The Influence of Fillers on the Biodegradation Kinetics of Polymers
Filled biodegradable polymer samples were prepared and exposed to simulated composting environment and the degradation kinetics was characterized. Particularly, the influence of the fillers on the biodegradation kinetics was investigrated.
Explosion of an ABS Pressurised Air Line
A compressed air line exploded suddenly and caused extensive damage to property, fortunately without casualties. The air line was used as part of a plant for annealing glass, and so was pressurised regularly up to about 10 bar. When the pressure was released, a blast of cold air was directed over the hot glass surfaces. Most of the pipework for the system was made of ABS pipe and solvent-welded fittings. The explosion was caused by catastrophic growth of an internal axial crack in one of the pipes of the system. The inside surface of the pipe was covered with deep cracks, and the first investigators concluded that the cracks had been caused by fatigue. However, a separate investigation of the remains indicated that traces of fluid from the oil of the air pump compressor had created environmental stress cracks.
Harnessing Natural Polymers and Fibers for the Development of Biocomposites
Economic and environmental forces are providing an impetus for the development of biocomposites from renewable agricultural byproducts. In pursuit of this goal, we are developing biocomposites from wheat-, kenaf-, and corn-byproducts without external additives. Our differential scanning calorimetry (DSC) measurements suggest that micronized wheat straw and inner kenaf fibers have similar thermal characteristics at 50°C < T < 400°C, thus they can be co-processed. The flexural strength of the composites formulated from micronized wheat straw and kenaf fibers increases as the concentration of straw in the composite increases. Postcuring the composites at 190°C also decreases the strength.
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