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.
Characteristics and Performance of Starch-Poly- (Vinyl Alcohol) (PVA) Blends with Agricultural Waste Fiber
The renewable polymers are environmentally friendly and naturally biodegradable, and could serve as an inexpensive source of raw material for single-use engineered products. Efforts are underway to develop ecocompatible consumer plastics by incorporating renewable polymers as an alternative to petroleum-derived chemicals. Therefore, gaining fundamental understanding of biobased polymers is critical for the design and development of consumer products. The research efforts at the USDA laboratory pertaining to the development of biopolymer blends, polymer processing, characterization and lifetime evaluation are presented.
Characterization of BMI-Carbon Fiber Composite Microcrack Development under Thermal Cycling
The objective of this research is to determine the effect of thermal cycling on the development of microcracks in BMI-carbon fiber composites (5250-4 RTM / IM7 6K 4-harness satin weave fabric). By clamping composite specimens on the radial sides of two half cylinders having two different diameters (127mm and 70mm), two different pre-stresses (-0.4 to 0.4 GP and -0.7 to 0.7GPa) are applied to the composites. Three different thermal cycling experiments, 1) –196°C to 250°C, 2) 23°C to i)150°C ii) 200°C iii) 250°C, and 3) -196°C to 250°C were performed as a function of pre-stress, number of thermal cycles, heating or cooling rate, and humidity conditions. An in-situ monitoring microscope is used to observe the microcrack development under synergistic stress, time, and temperature conditions. The experimental results suggest that there is a higher probability of microcracking with increasing number of thermo-cycles, higher pre-stress and humidity. A mathematical model considering residual stress and pre-stress is suggested to predict the microcracking under environmental conditions.
Investigating Environmental Stress Cracking with In-Situ Contact Angle Measurements
This paper probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized swelling induced by stress on the polymer. The system chosen for study is polycarbonate with oleic acid. An experimental technique involving contact angle measurements of a sessile drop as a function of stress is presented. A novel technique for contact angle measurements using refraction is also introduced.
Layout Design of a Platenless Molding Machine
A layout design of a platenless injection molding machine is developed. The machine design is motivated by economics, energy efficiency, compactness, ease of use, and environmental friendliness. The elimination of traditional platens allows for significant performance improvements as well as flexibility of new injection system and mold designs. This paper establishes theoretical feasibility, but also indicates that the design is most appropriate for clamp tonnages less than 150 tons due to actuator power and mold deflection limitations.
Low-Cost Composite Materials from Post-Consumer Plastics and Waste Paper
Composites of post-consumer plastics and high volume fraction waste paper have been studied. Various production techniques have been tested, with an optimum processing method defined, allowing the manufacture of low-cost composites of up to 60% paper content. Results indicate increases in tensile, flexural and creep modulus and flexural strength compared to the matrix can be achieved without the requirement of additives, with only marginally lower tensile strength and brittle impact behavior.
Controlled Epoxy Network Structure-Property Relationships: The Effect of Chain Termination
While epoxy thermosets are commonly used and are best known for their high glass transition temperature (Tg), creep resistance, environmental resistance and high stiffness, they are extremely complicated and intractable to thorough investigation. This is in part due to the fact that these are curing systems and gelation marks a turning point in the system’s performance as well as ability to be probed for effective structure-property relationships. In addition, practical formulations often contain multiple components that have subtle but important interactions to the final performance.In this presentation we will cover work that was performed recently to quantitatively probe the effect of one such practical yet important effect, namely chain termination. The effect of the size as well as flexibility of the chain termination group will be examined via a controlled host matrix chemistry that comprises of DER™ 332 as the epoxy, bisphenol A (BA) as extender and tris(4- hydroxyphenyl)ethane (THPE) as a crosslinker. Data and trends pertaining to Tg, stiffness, yield strength, fracture toughness and thermal expansion coefficient will be discussed.
Controlling the Performance and Rate of Degradation of Polylactide Copolymers
An important factor in the commercial development of biodegradable polymers is the ability to control the rate of degradation. Ideally, the polymer should not degrade during functional use, but degrade quite rapidly when discarded. This paper discusses various aspects associated with the control of the rate of degradation of polylactide copolymers; both from the perspective of stabilizing the polymer during processing and product use, and subsequently accelerating the rate of degradation after disposal. Of particular interest are the influences of molecular weight, crystallinity, end-capping and plasticization.
Creep Prediction Using the Non-Linear Strain Energy Equivalence Theory
The Non-Linear Strain Energy Equivalence Theory, a semi-empirical model, is utilized to predict long-term creep from short-term compressive stress-strain experiments conducted at different strain rates. Stress-strain experiments in uniaxial compression are performed at strain rates of 3 and 0.03 %/minute to predict creep behavior and stress-strain data at several strain rates for an immiscible polymer blend of recycled fractional melt flow high-density polyethylene and recycled polystyrene. The creep behavior is predicted up to 50 years at stress levels of 400 and 800 psi.
New Capillary Viscometers for the Compounding Industry
New Capillary Viscometers, beyond offering remarkable precision, may also broaden the characterisation of polymer compounds.After a short review of the features of recent equipment, some selected examples of applications will be shown. They range from improved quality control of incoming and outgoing products, to recycling management, masterbatches characterisation, and evaluation of dispersion effects on filled materials.
Degradation Studies of PLA Films Grafted with Hydrophilic Polymers
Poly(lactic acid) (PLA) is being investigated vastly due to its biodegradable and biocompatible nature. However, the degradation of PLA is slow, often leading to a long life-time in vivo. The major objective of this research is to modify PLA film surfaces with the ultimate aim of making a bioactive surface that will show faster degradation. The PLA film was solvent cast and the film surfaces were grafted with poly(acrylic acid) (PAA) using a UV induced photopolymerization process. The films were incubated in different pH solutions, viz., pH = 4, 7, and 10, for a specified time period. The film resulting from each treatment was analyzed using Transmission-FTIR spectroscopy and Atomic Force Microscopy (AFM). The molecular weights of the films were measured using gel permeation chromatography (GPC). Results established that faster degradation of the PLA film when incubated in different pH solutions could be achieved by surface modification of the PLA film by grafting PAA.
Design, Fabrication, and Assembly of a Polymer Electrolyte Membrane Fuel Cell (PEMFC)
This report will include the way to design, fabricate, and assemble a Polymer Electrolyte Membrane Fuel Cell (PEMFC) to maintain a low voltage source, near one volt, that runs at operating temperatures near 80 degrees Celsius. Creating a stack of cells will provide an energy solution that is more efficient than the system in place today. The PEMFC runs off of pure hydrogen and air (oxygen) and will provide a power source that is non-pollutant and renewable since hydrogen is readily available through the electrolysis of water. The problems with this experiment are maintaining moisture control on both the cathode and anode and the other problem is in controlling the hydrogen gas supply since hydrogen is very explosive when combined with oxygen. With these problems taken into consideration the PEMFC could be the energy source for the future.
Development of an Environmentally Friendly Solventless Process for Electronic Prepregs
The most common commercial processes for manufacturing pre-pregs for electronic boards use solvent-based resin systems. Solvents are environmentally unfriendly and contribute to voids in the pre-preg and laminate. The resin impregnation process is done in an open resin bath. This low-pressure impregnation is conducent to voids in the prepregs. Voids cause product variability, which is a major source of scrap in board shops. To eliminate the above mentioned drawbacks, a solventless process, based on the concept of injection pultrusion, is developed. The impregnation is done in a die under pressure to minimize voids.In previous work, chemo-rheological and kinetic measurements were used to identify a potential epoxy-based resin system. In addition, flow visualization using model fluids was used to establish the basic flow mechanism. Here, we use the previous results to develop a mathematical model for the B-staging process. Based on the mathematical model, three potential alternatives to produce prepreg are developed and analyzed. A prototype B-staging die is built and used to verify the mathematical model. The result shows that the model agrees well with the experimental data for low pulling speed and slightly under predicts the high pulling speed runs.
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.
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