SPE Library
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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Recycling
Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Pressure Shear Pulverization (PSP) Process for Thermoplastic and Thermoset Waste
A novel process of pulverization known as Pressure Shear Pulverization (PSP) process has been developed for thermoplastics (PE, PP, PS, PVC, PA, PET and/or their mixtures), thermosets (polyurethanes and phenolics), composites, and various blends (thermoplastics and paper). PSP is a proprietary, non-extrusion process and is realized inside a specially designed pulverization head. It is very different from cryogenic grinding, various versions of solid state shear extrusion (SSSE), and other size reduction processes. PSP has several advantages, namely, high output, low specific energy consumption, and low cost of pulverization head. PSP process is capable of producing coarse to very fine particles by manipulating the processing parameters. This paper deals with the development of pulverization of pre-consumer cross-linked LDPE foam waste and LDPE/Paper mixture by PSP process. As a model system, the processibility and properties of virgin LDPE have been studied. Physical properties of LDPE foam waste and polymeric powder have been determined and compared to understand the behavior of polymer under the combined action of thermally and mechanically induced stresses. Lab-scale and pilot-scale PSP machines have been designed and constructed.
Processability and Trends in the Mechanical Properties of Low Density Polyethylene Parts Produced Using Increasing Levels of Commingled Recyclate as a Filler
As the plastics industry is increasingly confronted with environmental demands and regulations, the need for successful and reliable recycling programs is greater than ever. One of the keys to the success of these recycling programs and to the success of recycled resins is identifying feasible end uses for commingled recycled polymers. One possibility is for plastics manufacturers to specify commingled recycled resins, as a filler, in their products. This can provide savings for the manufacturer, while helping to promote plastics recycling. When specifying the level of commingled recycled resin to be used in a product, the designer must consider the net effect it will have on the processability and the mechanical properties of the part. This study will examine and attempt to predict the net effect of increasing the level of commingled post-consumer and post-industrial recyclate, used as a filler, in the production of low-density polyethylene parts.
Rapid Heating and Curing of Structural Adhesives by Infrared and Radio Frequency
Structural adhesive requires a considerate curing time to achieve handling strength at room temperature. Conventional heating and curing methods are unable to cure adhesives in minutes because of the slow heat input rate to the system. Infrared heating can penetrate into the adhesive to accelerate the reaction process in a very short time. Radio frequency heating produced substantial energy input to the adhesive through the dielectric loss of the polar molecules under rapid changing electric field. The effect of operating parameters on green strength produced from these methods were studied and compared to that cured at room temperature. Both methods show significant reduction in cure time to obtain a strong bond in less than three minutes.
Recycling of Xerographic Toners
The objective of this research is to find ecologically and economically acceptable routes to utilize excess xerographic toner from manufacturing and returned toner cartridges. This black toner is a polymer composite comprised of a styrene-based copolymer, carbon black and other additives. The mechanical properties of toners are specifically designed to allow attrition to 10-20 µm particles. Thus the bulk mechanical properties are not desirable for load bearing applications typical of consumer plastics. Reactive and non-reactive blending of toner with other polymers have been used to enhance the mechanical properties. The blends and alloys produced exhibit a transition from brittle to ductile behavior as exhibited by impact energy data. Thus a family of polymeric systems of variable properties versus cost compromise can be created.
Reusing XLPE from Electrical Cable Waste: Cable Separation, Processing and Blend Properties
The recycling of power transmission cable was investigated by using different kinds of separation and reprocessing methods. The cross-linked polyethylene (XLPE) insulation of the cable, serving as a part of a broader study of the reprocessing of cross-linked thermoplastics, presented a specific challenge in separation. Separation of the XLPE from the other components of the cable was attempted by thermo-chemical, microwave and thermo-mechanical means. All three methods were able to separate the cable, and the relative advantages and disadvantages are discussed. Following separation, the following processing techniques were attempted: compression molding, extruding, and injection molding with and without preheating XLPE crumb. It was found that by preheating the XLPE and injection molding with high injection pressure, the neat XLPE could processed. Possible mechanisms for the flow and reconsolidation of XLPE crumb were hypothesized and investigated. Blends of XLPE crumb (0.3 to 3 mm particles) in either HDPE or LDPE were prepared and the tensile properties were evaluated.
Snap Tie Cones Made from Recycled PET and HDPE
To address the growing environmental concern, Santa Clara University's Plastics Recycling Laboratory chose a relatively inexpensive product with low structural demands to open a new market for 100% recycled material products. Snap tie cones, used in construction to space wall forms prior to pouring the concrete, were injection molded from recycled PET and HDPE and tested against the cones used in industry made from HIPS. Four tests- dimensional checks, compression, impact, and creep- were designed and conducted. The commercial cones along with ones made of recycled PET and HDPE were tested before and after ultraviolet (UV) exposure. The data analysis shows that the recycled PET cones outperform their industry counterpart, while recycled HDPE did not perform as well. This leads to the conclusion that recycled PET is a viable alternative to HIPS in this application.
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.
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