SPE Library

Plastic packaging forms a significant portion of household waste, and PET soft drink bottles represent a major percentage of the waste. Consequently, PET bottle grade material makes up a significant portion of the feedstock in the recycling plant at Visy plastics. The end uses are theoretically many, however, there are few applications for less purified grades of recycled PET. This paper presents the preliminary results of an industry based collaborative research project which aims to investigate the breaking down of recycled PET into its chemical building blocks using glycolysis. The main objective is to produce a polyester polyol for the polyurethane industry from recycled PET and to compare the properties with that of a virgin resin.

Blends of PA and PET do not have a minor significance in industrial production any more. Especially since the European beverage industry decided to use (multi- and single layer) PET bottles containing PA, the economic and ecological interest in recycling PA and PET is stringently increasing. In former research projects, where IKV has been involved, the compatibilization of PA and PET in extrusion was simply established. New investigations, focussing on the process optimization, enable to correlate the process parameters with the material properties. Therefore an extruder cascade was developed for a one-step-in-situ compatibilization and in addition a new characteristic parameter was constituted which is independent of the type of extruder.

A new solid-state mechanochemical technology is being developed to create value-added materials from post-consumer plastic waste. The process, called solid state shear pulverization (S3P), can recycle various mixtures of ordinarily incompatible plastics, including post-consumer film waste, by subjecting the polymers to high shearing forces in the solid state. This produces uniform, light-colored powders of variable fineness suitable for processing by all conventional plastic fabrication techniques. The resulting materials consistently exhibit high elongation and impact strength. Northwestern University and Material Sciences Corporation are transitioning S3P from the laboratory to the commercial scale.

Studies estimate there are two billion scrap tires in U.S. landfills with over 270 million tires added yearly. An overview of a simple technique for recycling thermosets will be discussed. In short, it is possible to recycle rubber powders made from scrap tires with the application of only heat and pressure and achieve good mechanical properties. An investigation of the mechanical properties of typical consolidated rubber powders as a function of the molding variables is be shown. To date every type of cross-linked elastomer investigated could be sintered, including silicone rubbers, natural rubbers, ethylene-propylene-diene rubbers, styrene-butadiene rubbers and fluoroleastomers.

This study was part of a program of work undertaken to develop recycling technology for multi-layer films which are not currently recycled. These multi-layer films comprise barrier layers with surface layers for mechanical strength, and tie layers between. Crosslinking is used to enhance various mechanical properties. The crosslinked layers have a high viscosity which creates processing problems, eg. if the film is recycled, high processing pressures are required. Furthermore, material blend component incompatibilty can result in inferior mechanical properties. Monolayer films of the virgin materials were produced. Multi-layer film with crosslinked EVA/LLDPE and a barrier layer was produced on a blown film line. This multi-layer film was agglomerated" then reprocessed in a twin screw extruder with virgin LDPE and LLDPE and blown into film. The blend miscibility was then determined using a TA Instruments TMDSC. It was found that LDPE blends were initially miscible with the containing scrap whereas LLDPE blends were immiscible. The LDPE miscibility was partly reversible as the blend components phase separated after the second heat treatment during testing in the TMDSC instrument. The initial miscibility was attributed to being induced by high shear during processing."

This paper describes the process for removing barrier layers and coatings (oxygen and carbon dioxide) from polyethylene terephthalate (PET) substrates through a conventional mechanical bottle recycling system. Varied wash chemistry and barrier medium have been examined and the effect on residual multilayer material or coating has been evaluated. Wash chemistry was found to be the controlling factor in improving the external coating removal efficiency. Delamination through mechanical working was found to be the controlling mechanism for separating multilayer materials. The conclusion drawn from our experiments is that the PPG Bairocade coatings were removed most efficiently. Internal deposition techniques may contribute fewer residues to the RPET, however substantiating this is difficult.

Thermoset recyclate fillers are considered as microcomposite reinforcements for polymers. Emphasis is given to glass fibre-reinforced phenolic and polyester waste products as functional fillers for polypropylene, where with appropriate surface modification, significant enhancement in mechanical properties can be achieved. In this respect, the role of a two component treatment package is discussed, in terms of fibre-matrix interfacial bonding, the effect on properties of the host polypropylene matrix, and the failure mechanism induced. Novel integrated compounding technology is described for the cost-effective preparation of polymer composites, containing thermoset recyclate fillers.

Rheological tests measure melt-state polymer flow, delineating molecular structure and predicting extrudability. Rheology of compounds used in fiber optic (FO) cable jackets and in the conduits that contain such cables will be our focus. Polyolefin-based jackets strengthen the FO cable and protect internal components, while the conduit provides long-term strength and protects the cables against environmental stresses. High density polyethylene use in these applications is growing rapidly, spurred by FO cable growth. Important properties in both applications include melt-state processability, stress crack resistance and solid-state stiffness. Melt rheology directly influences processability, combining with crystallization behavior to dictate final solid-state properties.

An investigation was conducted to evaluate replacements for methylene chloride in the solvent welding of an acrylonitrile-butadiene-styrene system (ABS) and a high-impact polystyrene (HIPS). Fourteen candidate solvents were experimentally considered. These were divided into three general categories: traditional, green and clean." A relative hazard rating was assigned to each solvent by taking the maximum concentration that the solvent could keep in equilibrium in a specified air space and dividing this value by the threshold limit value (TLV). Solvent welding was tested in both bond-in-tension and single-lap shear geometries. Parameters affecting resultant bond strength that were quantified included time polymer in contact with solvent time after surfaces joined temperature (pre- and post-bonding) contact pressure and vacuum."

This paper presents experimental results on the blends of polypropylene (PP) with functional polyolefin elastomer (FPOE) for recycling of xerographic toners. All experiments were carried out in a co-rotated reactive twin screw extruder. The investigation of the mechanical properties and morphology for different blends consist of PP, xerographic black toners and functional POE (FPOE) through reactive compounding. It is of interest to note that the notched Izod impact resistance of the blends with functional POE (FPOE) is significantly improved relative to physical blends. However, tensile strength at yield (?y) and modulus of elasticity (E) of the reactive blends are reduced. The reason why the impact properties should be so is clearly shown by the stress-strain behavior of the blends. Morphology of the cryogenic fracture surfaces of the blends was studied through scanning electron microscopy (SEM). The results of morphological studies indicated that not only the domain size of the phase of black toners could be reduced but also the interfacial adhesion could be enhanced through proper functional POE (FPOE). The phase morphology of the blends also illustrated that better dispersion of black toners could be obtained through using FPOE whereas serious agglomeration of black toners was found in the physical blends. It is elucidated that the functional POE could be an excellent candidate of compatibilizer for recycling xerographic black toners.

What if the electronics industry used specially designed photoresists that could be deposited using a spin coating process based upon liquid CO2 instead of organic solvents? Also what if this industry didn’t have to use hundreds of millions of gallons of water per day to remove sub-micron particles during the manufacture of integrated circuits and flat panel displays? Imagine polymerizing monomers in a continuous stirred tank reactor with the resulting polymers instantly dry, avoiding the trillions of BTUs needed every year to dry commercial polymers made in aqueous reaction media. Imagine an automotive industry that doesn’t expose its employees to toxic chlorinated solvents during metal degreasing processes. Imagine a textile industry that doesn’t need to use 100 lbs of water for every 1 lb of yarn that was dyed. Imagine local dry cleaners that don’t need to clean garments in perchloroethylene and local businesses that don’t need to pay exorbitant, newly enacted taxes on solvent use or carry newly mandated liability insurance policies. What if the demands on municipal water systems and municipal waste water systems could be dramatically reduced by changes in manufacturing technology? Imagine an educational environment where students become grounded in the fundamentals of their core disciplines, are exposed to cutting-edge, multidisciplinary science, and can experience the satisfaction and excitement that comes from doing research that makes a difference to society. The discussion will focus on the latest developments from the NSF Science & Technology Center for Environmentally Responsible Solvents and Processes. In particular, the detailed synthesis and CO2 solution properties of fluorinated and siloxanebased homopolymers and block copolymers will be discussed. The utility of such macromolecules will also be demonstrated for use in coatings (photoresists and textiles), separations, stabilizers for polymerizations, and scaffolds for catalysis. Particular attention w

This paper reports the results of an investigation of the effects of purity level and nature of impurities on the properties of recycled polycarbonate and recycled acrylonitrile-butadiene-styrene polymers blended with the corresponding virgin resins. The relevant thermal, mechanical and flow properties were measured. It is concluded that properties of recycled polymers depend not only on the amount of impurity present but also on the kind of impurities and contaminants that are present. The latter factor even plays an important part in relation to compatibility of polymers. However, polymer melt rheology seems less sensitive to impurities than some mechanical properties such as impact strength. More than 99% purity is needed for recycling these polymers back into their original, high-value applications.

Failure analysis (FA) of products and materials always requires careful observation of the general circumstances involved. The product failure analyst never overlooks external causes or environmental effects. All FA also requires a healthy dose of common sense and a 'Sherlock Holmes' investigatory sense. However, specialized material and product tests are also essential components of successful FA including: material mechanical properties, tests for composition and uniformity, residual stress tests, tests for contamination, identification and quantification of residual solvents, microstructural examination, and many more. An overview of general FA techniques will be presented, followed by specific examples of plastic FA. These specific examples will be discussed in detail, with special emphasis on the key findings derived from specialized laboratory testing. Examples will include plastic piping systems, consumer products, industrial equipment, and sporting equipment. Techniques discussed will include residual solvent identification by GC/MS, various spectroscopic techniques, optical and electron microscopy, thermal analysis, and mechanical properties testing.

This paper investigates the melting point and crystallinity behaviour of blends of recycled milk bottle HDPE with injection moulding and film blowing grade high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) as part of a larger investigation into blends of recycled HDPE and virgin polyolefins. The variation in melting points and crystallinity levels for blends of recycled HDPE with either HDPE or LLDPE were linear with composition, and displayed only one melting point, while recycled HDPE with LDPE displayed separate melting points for each compositional component.

Because of their previous thermal and shear history, recycled plastic materials have properties that are significantly inferior to those of their unrecycled counterparts. Thus, the applications of these materials are limited. With the aid of Vibration-Assisted Injection Molding (VAIM) technology, during the present study the properties of products made from recycled polymeric materials were improved. In this paper, the property enhancements realized with recycled polystyrene are presented compared with those obtained through the convention injection molding of virgin material. Also, a potential theoretical basis for the phenomena is discussed.

Polypropylene, as a commodity recyclable thermoplastic, is studied in this research to evaluate the potential environmental impact resulting from volatile organic compounds (VOCs) emitted during multiple reprocessing. Unstabilized commercial polypropylene (PP) grade was processed several times by injection molding. Samples were examined after each cycle for total VOCs emissions with a flame ionization detector (FID) and cumulative VOCs emissions were obtained after each processing step. Corresponding structural changes were investigated with Fourier Transform Infrared (FTIR) Spectroscopy and results were correlated with rheological data that showed decreasing viscosity particularly after the 7th processing cycle.

Waste management is gradually becoming a priority within an integrated approach to nature conservation. Croatia has taken a number of good steps during the recent years. The first life-cycle and economy analyses in Croatia were made for managing of glass waste in 1997, but no serious study of plastic waste was made until recently. Among all types of plastic waste, only PET-bottles are collected in Zagreb (within the OHO system - Croatian Recycling System), so it was logical to make the first life-cycle analysis of PET-bottle. The results have shown the evaluation of PET-bottles' impact on the environment and the critical points" of PET-recycling were pointed out."

Commingled recycled plastic lumber (RPL) decking was exposed to the environment for eleven years. The weathering effect is examined by performing mechanical property tests on the full size deck boards before and after the exposure. Flexural tests on the weathered deck boards were conducted with the exposed side and the unexposed side tested in tension. The flexural properties after weathering are compared to the original flexural properties. These data show the effect of weathering on recycled high-density polyethylene based RPL. A life cycle cost analysis (LCCA) is also presented to compare the cost of a wood deck versus an all RPL deck. The purchase, maintenance, and disposal costs are included.

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.

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.