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.
Stress Relaxation of Polyolefin-Based, Oriented, Glass-Fiber Materials
Samples of recycled plastic lumber constituted of a mixture of two different polyolefins and an inorganic glass were subjected to short-term stress relaxation tests. In addition, stress-strain tests were carried out at different rates of stress and strain for both full-sized lumber profiles and smaller samples machined from the larger pieces. The results from the short-term stress-strain tests were used in conjunction with a mathematical model to calculate values of stress as a function of time for the relaxation experiments. Calculated values are in good agreement with experimental stress relaxation data. The feasibility of extending this model to predict long-term time-dependent behavior is discussed.
Study on the Processability of Recycled PET Fiber
Recycled poly(ethylene terephthalate) (R-PET) used in blends with a fiber grade material (F-PET) has been investigated in this paper. As-spun fibers of R-PET, F-PET, and R/F-PET blends were made at winding speeds ranging from 1000 to 4000 m/min (mpm), and subsequently drawn in the range of 5.4 to 1.35X to bear the same total extension ratio. The properties of fibers spun at high and low wind-up speeds with low and high extension ratios have been compared in terms of the orientation, crystallinity, and mechanical properties. The fully oriented yarns (FOY) prepared from R-PET show a tensile strength of 90% of the fiber grade, with 4.4 g/d (R-PET) to 4.8 g/d (F-PET). On the other hand, R-PET fibers spun at low wind-up speed with high extension ratio show better physical properties than that spun at high wind-up speed with low extension ratio, with 4.4 g/d (1000 mpm/5.4X) to 3.7 g/d (4000 mpm/1.35X). The results indicate that for R-PET material, the low wind-up speed with high extension ratio process provided advantageous environment for developing crystalline fiber structures.
Testing of Recycled PET Rebar Chair
Small chairs for supporting reinforcing steel in concrete slabs were molded from recycled PET. The performance of these chairs was tested relative to plastic chairs available on the market. Four tests were used to evaluate the chairs. The tests were designed to evaluate impact, compression, and UV degradation strengths of the chairs, as well as the adhesion between the PET and concrete. The recycled PET chairs performed better than commercial chairs under compression, but did not allow for flow of the concrete. The impact performance of recycled chairs was very comparable to the commercial chairs. UV results are embedded in the impact and compression tests.
The Centrifuge - An Alternative to the Filter for Highly Contaminated Polymer Melts
The recycling of thermoplastics gains more and more importance. For removing the contamination one-or-two step filtration units are state of the art, but due to high material loadings or running costs they often reach their limits. Therefore IKV examines whether a centrifuge, which is fed with polymer melt, might be an alternative. In preliminary tests IKV showed that centrifuges built for low-viscosity materials can also be used for polymer melts. A centrifuge was installed into an extrusion line. Up to 10 weight-% of contamination could be removed out of the polymer melt successfully.
The Composite Sidewalk
Plastics affect every aspect of our lives. Plastics is used and discarded everyday. What this theory addresses is how the use of discarded plastic has developed another method to recycle plastics material. Using plastic regrind in composite mixtures not only provides an alternative filler or reinforcement, but it also is a better way to recycle the discarded materials. Taking this theory into consideration, the Shawnee State University Plastics students developed a composite sidewalk using plastic regrind replacing the aggregate in concrete mixtures. The purpose of this paper is to discuss the installation and manufacturing techniques as well as the durability of the sidewalk over the past year.
The Development of Polyolefin Based Oriented Glass Fiber Building Materials
In 1994, Rutgers University’s Plastics and Composites Group, formerly the Center for Plastics Recycling Research, was grant funded by the New Jersey Commission on Science and Technology to develop and test composite railroad ties made from recycled plastic. Since the inception of this project, the major participants have been Rutgers University, US Plastic Lumber Corporation (formerly Earth Care Products, Inc.), Conrail, Norfolk Southern, Washington and Lee University, and the US Army Corps of Engineers. Though the main goal of this research was to produce plastic lumber with properties required of railroad ties for substitution with creosote treated oak, the project participants knew that many other applications could utilize this material as a direct substitute for wood. A direct result of this research was the discovery of a way to orient a high percentage of short, random length glass fibers along the axis of flow in a mold. U.S. Patent 5,789,477 was granted August 4, 1998 for this discovery, and we are sharing the information here.
The Effect of Phenolic Regrind on the Mechanical Properties of HDPE
The possibility for recycling cured phenolic material was evaluated by testing mechanical properties of High-Density Polyethylene (HDPE) containing phenolic regrind material. The mechanical properties evaluated were: modulus of elasticity, percent elongation, tensile strength, and impact strength. Four different levels of phenolic regrind were used for evaluation with four different levels(4.76, 9.09, 16.7%) of phenolic regrind used in the comparison. The results demonstrated that with higher levels of phenolic regrind in the base HDPE material, certain mechanical properties degraded, with increased brittleness the most apparent effect.
The Effect of Polyvinyl Chloride and Polystyrene on the Mechanical Properties of Plastic Parts Produced with Commingled Post-Consumer Recyclate
One way to avoid the separation of post-consumer plastic waste is to utilize commingled recyclate in the design of plastic products. However, the combination of many plastic resins can sometimes yield poor mechanical properties, due to the debonding of the different resins. It is important to understand if one or more resins in the commingled material will cause greater debonding than the other resins. This study examines the debonding in low-density polyethylene specimens filled with increasing levels of commingled post-consumer recyclate that does and does not contain polyvinyl chloride and polystyrene. The debonding in the specimens will be characterized through tensile testing.
The Effect of Recycle History on the Performance of Neat, Filled, and Reinforced Nylon 6
The recyclability of any thermoplastic will be influenced by a large number of variables. One factor that influences recyclability of a thermoplastic is the material formulation itself. This is particularly true when additives such as reinforcements are incorporated into the base resin. Reinforcements such as glass fiber are widely used to enhance the stiffness, dimensional stability and elevated temperature capabilities of thermoplastics. It could be said that these reinforced thermoplastics are somewhat less recyclable than their neat counterparts due to the fiber degradation that occurs during processing and regranulation. Mineral filled thermoplastics can be an alternative to reinforced thermoplastics in some of these applications. While mineral filled compounds are not equivalent to the fiber reinforced formulations, they are more recyclable since minerals tend to retain there physical form during processing and regranulation. In this study, the effect of recycle history on the properties of neat, mineral filled, reinforced, and fiber I mineral hybrid nylon 6 has been evaluated. The neat, mineral, and hybrid materials have been shown to exhibit better property retention than the glass reinforced nylon when subjected to multiple recycle histories.
The Influence of Polypropylene Content on the Properties of Post Consumer Recycled High Density Polyethylene
Polypropylene (PP) from bottle caps is present in High Density Polyethylene (HDPE) in post consumer recycled resin, and it acts to reduce the overall toughness. This study is concerned with quantifying the influence of PP on the physical properties of recycled HDPE resins and evaluating toughening recycled HDPE/PP blends by the addition of metallocene catalysed linear low density polyethylene (m-LLDPE). The toughness of HDPE was found to decrease significantly with as little as 5 wt% PP, and at 20 wt% the toughness was reduced to levels comparable to that of PP alone. The addition of m-LLDPE was effective in increasing the toughness of the blends to values comparable or greater than those of recycled HDPE alone. The principal mechanism seems to arise from the suppression of crystallinity of HDPE matrix for levels of up to 20% m-LLDPE, and the introduction of amorphous phase content within the samples.
Thermal Aging Effects on Transport Properties of Polymeric Membranes for Fuel Cell Applications
Although solid polymer electrolyte fuel cells have been considered as environmentally attractive power sources, to date little work has been done on the durability of eletrolyte membranes. It is conceivable that time and prolonged exposure of membranes to elevated temperatures will significantly diminish the effectiveness of electrolyte cells. The goal of this study is to investigate and compare thermal aging and morphology effects on transport properties, such as ion diffusion coefficients and permeability parameters of the membranes for hydrogen ion transfer, of commercially available Nafion® and Dias® membranes and experimental phosphorus containing polyimide membranes. The emphasis of this paper is placed on the design and properties of a diffusion cell necessary for hydrogen ion measurements.
Thermoforming Behavior of Olefinic Instrument Panel Skins
Currently thermoplastic olefins (TPO) are being used for injection molded or extruded automotive exterior parts. Due to lack of melt strength of the polypropylene base resin, the thermoformable TPO are still under development for automotive interior skins. The advantages of TPO skins over the current PVC/ABS skins are long term aging, reduced fogging, and improved recycling. Laboratory evaluation for formability usually involves uncommon and tedious tasks. In this study, dynamic mechanical analysis in tension mode was used to predict the optimum temperature range for thermoforming, extent of network enhancement, as well as other mechanical properties.
Thermoplastic Pultrusion Based on Isoplast Engineering Thermoplastic Polyurethanes
Fiber reinforced composite materials are finding application in an ever increasing range of markets. The bulk of the composite materials is based on a thermoset resins combined with glass roving and/or glass mat as continuous reinforcement. Glass filled thermoplastic resins are limited mainly to discontinuous reinforcement and therefore used primarily in injection moulding applications. Despite potential performance and environmental benefits linked to continuous reinforced thermoplastic composites, they have not been implemented on a large scale. This is because they have been lacking performance in comparison to thermoset composites. Thermoplastic composite materials are a class of structural materials waiting to happen, the results booked ??with the process and material described in this paper show that a significant step forward has been made in developing them.
TPE Overmolding Compounds for the Next Millenium
This paper describes the use of TPE compounds for over-molding on to engineering thermoplastic resins. These TPE compounds have a wide range of hardness and are bondable to a wide spectrum of engineering thermoplastic and engineering thermoplastic elastomer substrates. They exhibit very smooth, tack-free, mar resistant surface for the very soft compounds. The bonding between the TPE and the substrate resists environmental changes such as hot air aging and water immersion. The adhesion data and other physical data, adhesion quantification methods, suggested processing conditions and selected applications of these TPE over-molding compounds will also be presented. Theories in TPE over-molding or co-extrusion are discussed.
Trends in Automotive Plastics
This briefing on trends in automotive plastics will delineate the differences in plastics application areas between North American and overseas markets. The key themes addressed include: • Although mass savings are widely thought to be a key driver in metal replacement by plastics, increasingly automakers are more interested in the contribution of plastics to styling, occupant safety and comfort, and functionality. • Plastics are increasingly specified for their design freedom. They make possible the consolidation of parts and consolidation of functions, minimizing manufacturing costs while maximizing function and value. • Competition among automotive plastics is relentless and intensifying, resulting in improved forecasted growth for some plastics at the expense of others. • Plastics application trends will be compared between North America and overseas in four sectors: Interiors, Exteriors, Under the Hood, and Chassis and Powertrain. • Greater attention is being given to polymer composites in the U. S. for exterior body panels and some structural applications, with minimal interest in other countries. • Finally, more progress is being made in the recycling of plastic manufacturing scrap than in the recycling of plastic parts/materials from scrap vehicles. This is so because manufacturers have control over process scrap, which improves recyclability and the value of recycled materials. The use of plastics in vehicles is steadily increasing. This trend is expected to continue. On average, current vehicles use about 113 Kg (250 Lbs) of plastics and that amount is estimated to grow to 137 kg (300 Lbs) per vehicle in the next ten years. Historically, vehicle weight savings has been a primary driver in replacing metals with plastics on vehicles. However, today styling, end-use functionality, and better manufacturing economics through parts consolidation are the key factors in choosing plastics to replace other materials in vehicle applications. In addition, fut
Vibrated Gas Assist Molding: Its Benefits in Injection Molding
This paper shows how air or nitrogen can be used to impart vibration and/or pressure pulses to a melt. Air is already used to blow preforms and parisons  inside of molds, and to core out hollow articles in the process of Gas Assist Injection Molding . The methods of gas assist molding have demonstrated their great usefulness in injection molding not only to hollow parts out but also to induce an excellent surface finish. Melt vibration techniques have also been reviewed [3,4] and show great potential to reduce viscosity during filling and impart optical and mechanical benefits, i.e. stiffness, strength and clarity, without resorting to processing aids such as thinning or nucleating agents. The present paper explores the processing of injection molded plastics under gas vibration. Vibrated gas can be used for several purposes. 1. Gas can be inserted and vibrated in the mold prior to melt injection to modify the filling process mechanism, fuse knit lines, heal sink lines and other defects due to flow imperfections. 2. Compressed Vibrated Gas can act like a pressurized vibrated gas spring, which helps induce orientation benefits in the short shot during filling completion. 3. Vibrated air pressure, localized in specifically designed air-runners distributed around the runners and inside the mold, helps fill and pack the mold, core out hollow parts and balance flow in multi-cavity molds. 4. Vibrated Gas can also be used to tag parts for recognition during recycling or later inspection. The paper reviews hardware and controls requirements to apply this novel technique to injection molding.
A Biodegradation Study of Co-Extruded Nanocomposites Consisting of Polycaprolactone and Organically Modified Clay
Nanocomposites containing biodegradable polymers and clays were investigated to improve biodegradable properties. Polycaprolactone (PCL) (83,000 and 43,000 g/mol molecular weight) was mixed with additions of either 2 or 5% of synthetically modified montmorillonite clay. A twin screw extruder was used to produce the pellets. The pellets were then co-extruded with multilayering technology to produce 15-inch wide films from a 256 and 1024 layer die multiplier configuration. This study focuses on the biodegradation studies in compost, soil, and marine environment with results showing improved biodegradation rates in selective nanocomposites and environments.
A Study of the Tensile Creep Behavior of Recycled High Density Polyethylene in Aqueous Mediums
Recycled polymers are currently being used in the design of commercial products for the maritime structure industry. Marine pilings, pier fenders, and pier support elements are just some of the products being designed with recycled polymers. Understanding the effect of submersion in salt and fresh water on the mechanical properties of the material used in these products is important. This study will examine the tensile creep behavior of recycled HDPE in ocean water, fresh water from Lake Erie, distilled water, and air. A specially designed apparatus for aqueous creep testing was utilized to obtain the data for this study.
Blend of Post Industrial ABS and PMMA Improves Thermal and Impact Properties
The recycling of post industrial ABS and PMMA was investigated. A material compound consisting of 100% post industrial (PI) recycled ABS and multicolored acrylic (PMMA) scrap from a manufacturing plants was blended and extruded. Test samples were injection molded and the test results were correlated to virgin material. Additionally, the material was used in injection molding of rear lamp housings in black and gray colors. The test results and economics are promising.
Characterizing Scrap Vinyl Flooring to Determine Feasible Reuse Options
The manufacturing waste generated during the production of vinyl floor tiles is typically sent to landfills, rather than recycled, because of a lack of reuse options for this material. This waste is typically PVC loaded with approximately 80% limestone. The goals of this research are to characterize this material to determine the feasibility of reprocessing it and to measure the mechanical properties of the processed material. This study will also attempt to suggest an injection molding or extrusion application for the mixture.
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