SPE Library

It is well known that reprocessability of plastics is essential during both manufacturing and consequent recycling. Post-consumer materials, and in particular a five component blend of high- and low-density polyethylene, polypropylene, polystyrene, and polyvinyl chloride representing American film waste, have been successfully reprocessed multiple times by solid-state shear pulverization on a laboratory scale pulverizer. A processing cycle included pulverization, injection molding and conventional grinding. Physical properties such as notched Izod impact strength, elongation at break and flexural properties remained unchanged after four cycles. No change in color or surface appearance of the injection molded test specimens was observed.

There continues to be a need for additional uses of recycled plastics. A significant portion of recycling applications require outdoor exposure including use in aqueous applications. This paper covers the effects of water on the properties of recycled plastics under tensile loads. The paper also covers long term creep effects.

Neat resin bonded single-lap composite joint has been extensively used in composite structures. Lower strength and longer fabrication time have been identified as technical barriers in practice. In order to increase the joint strength and reduce the fabrication time, two types of prepreg composites were used to bond composite single-lap joints. Test specimens were prepared per ASTM D 3165-95 standard. Accelerated conditioning was conducted to investigate the environmental resistance of specimens. The shear strength of various specimens was obtained using tension tests. Compared to control specimens, prepreg bonded samples exhibit higher tensile strength, higher environmental resistance, and shorter fabrication time.

The sandwich injection molding technique can be used in wide ranges of engineering applications for recycle. In this study, flow behavior of core material in sandwich injection molding with sequential and simultaneous injection was investigated. Flow behavior of materials in sandwich injection moldings revealed to divided into four regions (Primary injection region, core advance region, core expansion region and break region). The flow length of core expansion region was increased with increasing of simultaneous injection time of skin and core material. And it is revealed that the core layer was formed as wide and thin structure with increasing of simultaneous injection time.

Three types of specimens of a polyester-amide and a poly-hydroxybutyrate have been tensile and tensile-impact tested. Important geometrical parameters for these specimens are wall thickness and gate dimensions, as well as a weld line in one specimen type. Explanation of the combined influence of geometry and injection molding settings on tensile behavior was in agreement with tensile-impact results. This influence was maintained after 20 months of storage in closed boxes but minor embrittlement was found for all specimen types and both materials. The beneficial effect of annealing on strain at break for all poly-hydroxybutyrate specimens was also shown.

The growth of the plastics recycling industry was spurred by increased resin prices and the landfill crisis of the 1980's. Many of the recycling companies that started in the 1980's and 1990's quickly learned that economic recycling of plastic waste was a difficult and challenging task. For many of these companies, the problems were overwhelming and they went out of business. Those that survived into the 21st century are a unique group of entrepreneurs. The bulk of the survivors are small companies with sales under $20 million.In this study, 36 plastic recycling companies in the U.S. and Europe were evaluated to determine the elements that aided their survival. Three elements that were present in the majority of these companies were: an ability to develop and maintain their own technology, financial or technical support from external sources, and strong leaders who were determined to make the business survive. These companies are the models for their industry. The stories of these companies could be of particular value to the emerging automotive and electronic post-consumer plastics recycling industry.

Small parts less than one quarter of a pellet require a complete rethink by molding engineers and mold designers. Total part cost justification becomes more challenging based upon the amount of material wasted and tooling costs. Micro machinery is helping to meet the requirements of accuracy through simplicity. There is no need for complicated multiple profile closed-loop servo controlled injection and metering functions.The two-stage plunger over plunger injection unit is capable of processing basic polyolefins to high temperature LCP materials. Shot pot injection provides accuracy of volumetric control by eliminating variation caused by slider or check ring shutoff inconsistency. The minimum number of components used in the design achieves simplicity.

The thermoforming industry has achieved a good understanding of the process, which has been in large scale operation since the 1950's. Consequently, control of machine settings such as heater band temperatures, plug position, plug and mould temperatures is quite advanced. However, to date, little work has been done to address the control of state parameters describing material behaviour during processing, such as sheet temperature and material distribution in the part. Control of state parameters is essential as material property changes, environmental factors and machine operating drifts can significantly change the dynamic operating point of the machine.

Conventional injection molding and Multiple live Feed Molding (MLFM) has been used to process starch based biodegradable composites aimed for load bearing bone replacement/fixation applications. Blends of starch with : (i) poly(ethylene vinyl alcohol) and (ii) cellulose acetate were studied. Both polymers were reinforced with bone-like ceramics (hydroxylapatite) in amounts up to 50 % wt.. The use of MLFM allowed for the inducement of molecular anisotropy into the moldings. However it was necessary to prevent material degradation associated to shear dissipation effects and to the longer residence times.

The need for biodegradable thermoplastics continues to grow as waste disposal remains an environmental problem. In order to meet these needs, alloying of biodegradable plastics may expand the markets in which they are used. Initial evaluation of mechanical properties of selected blends suggests that Biomax®, which is a somewhat brittle material, may be toughened by the incorporation of a low modulus copolyester, Bio® GP. Also, blends of CAPA® 6500 and Bio® GP offer a group of mid to low modulus biodegradable polymers. The suitability of blends of Biomax® and CAPA® 6500 are unknown at this time. Assessment of the mechanical properties suggests that miscibility is suspect. The addition of ECM Masterbatch Pellets® to a polyolefin is another approach for developing degrading polymers. The addition of the concentrate did not significantly change the mechanical properties of a polyolefin resin.

Automobile manufacturers are searching for ways to eliminate the traditional painting process employed in assembly plants to decorate and protect the exterior of an automobile. The entire paint facility in a typical assembly plant runs anywhere from $200 million to $600 million and can occupy 50 percent or more of the factory floor. Add to this the cost of environmental compliance, energy, raw materials and labor and it's easy to see why elimination of the paint operation can be a huge benefit to car manufacturers.GE Plastics has developed a polymeric film that can eliminate the need to paint. The film is a proprietary product of polyester carbonates based on resorcinol arylates. This film can be applied over a variety of substrates through an in-mold decoration (IMD) process to yield Class A, exterior panels and trim - that can then be assembled without the need for painting. This product generates an ultraviolet (UV) screener, which extends outdoor life. In addition to the weatherability, the material also exhibits improved scratch and chemical resistance over other thermoplastics.

The use of advanced lightweight materials to improve combat survivability has been of crucial interest to the U.S. Army for a number of years. The design, development, and performance testing of these advanced materials is critical for enabling Future Combat Systems and the Objective Force Warrior. Specifically, hybrid organic/inorganic polymer matrix nanocomposites show promise in providing many of the physical properties required (i.e. lightweight structure, rugged abrasion resistance, high ballistic impact strength). However, as with any polymer system, these materials are susceptible to degradation over time when exposed to various environmental (i.e. sunlight, moisture, temperature) conditions. This structural degradation (1-5) will eventually comprise the original integrity of the materials’ desired properties.Polycarbonate (PC) has outstanding ballistic impact strength, good optical clarity, and high heat distortion resistance. The Army has a continuous interest in research on PC for better chemical resistance and enhanced resistance to abrasion. The focus of our research is to exploit nano-technology through incorporation of layered silicates for property enhancement. Typical mica-like clays consist of stacked platelets with the thickness of each individual platelet on the order of 1 nm. (1-5) Because of the nanometer size and high aspect ratio characteristics, polymer-layered silicate nanocomposites with much lower volume fraction of clays exhibit properties significantly better than the conventional mineral-filled micro- or macro-composites.In this study, the impact of accelerated weathering upon newly developed polycarbonate-layered silicate nanocomposites materials was investigated. The silicate loading varied from 0-3.5 % by weight. A fluorescent ultraviolet (UV)/condensation weathering tester was selected for the exposure study. The materials were characterized by UV/VIS spectroscopy and FT-IR spectroscopy.The results reveal that the carbonate linkages

This paper presents the results of the development of recycled HDPE blends with improved SCR for low pressure pipe containing the maximum possible portion of post consumer recycled HDPE. A post consumer recycled High Density Polyethylene (R-HDPE) was blended with virgin Medium Density Polyethylene (MDPE), over the composition range of 0-100%. The recycled HDPE has limited post-consumer applications due to its poor stress crack resistance (SCR). Resistance to SCR of the compositions was determined by the Notched Constant Tensile Stress Test (NCLS). Results indicate that there is potential to incorporate the use of Post consumer HDPE in low pressure pipe applications at composition greater than 50%.

Biodegradable polymeric supports (scaffolds) have been used in tissue engineering in order to regenerate damage or lost tissue and organ structures.In this work scaffolds of poly (3-hydroxybutyrate) (P3HB), a natural polyester produced by bacterial fermentation process, were prepared by solvent - casting / particulate - leaching where the polymer was dissolved in organic solvent and mixed with salt particles of different sizes, followed by controlled solvent evaporation and water dissolution of the salt.The interconnected pore structure was evaluated by Scanning Electron Microscopy (SEM). Differential Scanning Calorimetry (DSC) was used to determine the thermal properties of P(3HB) / salt. SEM micrographs revealed the presence of interconnected pores for all ranges of salt particles. Thermal analyses showed that the degree of crystallinity for the porous structures was higher for lower salt particle size compared with P(3HB) dense film.

In order to develop a polycarbonate (PC)/ acrylonitrile-butadiene-styrene (ABS) product with a high content of recycled PC, a low molecular weight virgin PC was added to recycled PC to minimize batch-to-batch property variations in the compounded product. Six PC/ABS blends were prepared on a twin screw extruder by mixing 50 wt% virgin ABS and 0-25 wt% low molecular weight virgin PC with 25-50 wt% high purity recycled PC recovered from end-of-life electronics. These blends were characterized rheologically and mechanically. Results showed that this strategy could yield consistent quality resin blends with a high recycle content.

The reactive blending in melt state of poly(ethylene terephthalate) and sodium and zinc ionomers based on ethylene-methacrylic acid copolymers was investigated using a torque rheometer. The components were blended in mixer during 90 min for recycling simulation. The torque increases with processing time according to typical profiles depending on the metal type. Torque changes were attributed to chemical reactions between components generating high molecular weight species. In addition to PET degradation, the ionomers react with PET carboxyl or hydroxyl end groups forming graft copolymers and crosslinked species identified by multiple internal reflection (MIR) FTIR technique.

Crosslinking of polyethylene greatly improves the material's properties. The crosslinking process causes problems with the material's ability to be recycled. It prevents the material from remelting, making it nearly impossible to process in an injection molding machine.The crosslink density has an effect on both the material's ability to creep and on its ability to be recycled. Creep data was studied to determine the effects of increasing crosslink density on an injection molded polyethylene part. This data will be used as a baseline for how parts made from 25% recycled crosslinked regrind compares with the original crosslinked part. This paper will focus on recycling crosslinked polyethylene (PEX) determined by its creep data.

A methodology is presented for the reliability assessment of new product offerings, where product failures are driven by environmental conditions. The methodology is valid for the case of limited related product field data and understanding of underlying environmentally driven failure mechanisms. The methodology uses reliability theory in concert with failure mechanistic models to provide high resolution models which can be used to forecast liability exposure of new product offerings. The methodology has been successfully demonstrated for evaluation of Vinyl based products. The quantitative results generated suggest environmental region risks, overall new product risk, and risk relative to existing related products.

Polyphenylene ether (PPE) is a high cost material, starting at three times the cost of polypropylene, with the price only increasing as fillers are added. Plastic parts made of PPE with the additives carbon, talc, and mica could be reused as pure PPE if the additives were removed. A process was developed to separate the PPE from the additives, using a solvent that dissolves the PPE and leaves the additives as tiny particles. The mixture was filtered, allowing the dissolved PPE to pass through but retaining the additives. The reclaimed PPE can be sold for a profit and used to make new parts. Recycling the PPE saves millions of pounds of material from being dumped into landfills each year.

The solid state polymerization (SSP) of recycled PET from 2L bottles was investigated. The bottles were ground, washed, dried, crystallized and processed in a reactor under heating and nitrogen flow. The material was feed in the reactor as flakes and not in pellet form, so an extrusion step was eliminated. A systematic study of the influence of process conditions, like crystallization temperature, SSP temperature, reaction time and nitrogen flow rate was carried out. The weight-average molecular weight of the recycled PET were measured by SEC. Thermal properties and crystallinity were determined by DSC.