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Various topics related to sustainability in plastics, including bio-related, environmental issues, green, recycling, renewal, re-use and sustainability.
Method to Determine Screw Performance and Product Quality during Manufacturing Process
During the extrusion process, whether it is film, sheet or injection molding, the need to obtain consistent quality and output requires an extensive quality control program. Unfortunately, these operations are time consuming and wasteful, often requiring many pounds of extrudate be expended before the desired result is achieved.Also, as extrusion equipment becomes worn, output rates decline and product quality gradually falls, often going unnoticed, until significant problems occur.Thirdly, when a new screw purchase is required, time-consuming laboratory trials are normally set up to evaluate screws from different manufacturers before deciding the best one for that particular operation.To quickly assess changes in operation conditions, whether from day-to-day running, equipment performance or assessing new equipment, a concept has been developed for an extrusion product, which utilizes the principal of mixing two colors to achieve a homogeneous third color. Observing the homogeneity of the third color mix and the flow pattern it generates will indicate the screw performance and the quality of the product. This is a quick, efficient way to test the process without sacrificing product or running time.A series of experiments was performed to evaluate two different screw designs in an injection molding process. In addition, molded parts from the same mold but the different screw designs were evaluated for quality consistency. In a separate trial, the amount of wear on production screws and barrels in a color compounding process were evaluated.This paper is based on these experiments and prospective new products.
Modeling of In-Mold Coating for Resin Transfer Molding
Closed mold reactive liquid composite molding processes such as resin transfer molding (RTM) and any of its variations such as vacuum-assisted resin transfer molding (VARTM), Seemann Composite Resin Infusion Molding Process (SCRIMP), etc, are environmentally friendly alternatives to open mold processes, which have been traditionally employed to form large composite parts. However, in most cases, in order to improve and/or protect the part surfaces, gel coating is required. The gel coat is applied with the mold open, which releases harmful volatile organic compounds (VOCs) to the environment, partially compromising the benefits of the closed mold processes. In-mold coating (IMC) is an attractive alternative to gel coating to eliminate VOCs. IMC is a coating operation performed by injecting a coating material onto the surface of the substrate with the mold closed. The coating flows by compressing the substrate under pressure. In the present work, we develop mathematical models to predict the filling and packing stages of IMC for RTM substrates. These models include the effect of the compressibility of the substrate and mold.
Modification of Biodegradable Polyesters with Inorganic Fillers
Composites produced by solution mixing of a biodegradable thermoplastic polyester based on butylene adipate / succinate, as well as a commercial polylactic acid, with surface coated and uncoated hydrotalcite inorganic minerals were studied. Materials were also melt-mixed in a twin screw extruder for comparison. Significant structural and morphological differences were noted following characterization of the composites by DSC, TGA and melt rheology. Results varied depending on the materials and the processing methods. Biodegradability and biocompatibility were evaluated by performing tests “in vitro” in the presence of a phosphate buffered saline solution.
Non-Reactive Process for Recycling of Cellular Phones
The use and production of cellular phones have skyrocketed within the last decade, with the average use lifetime between 1 and 3 years. So, the ability to dispose of and recycle the phones is a pressing issue. These phones are composed of a variety of materials, including thermoplastics (six different types), metals, rubber, and epoxy. This work pertains to the grinding of cell phones, separation of thermoplastics and epoxy from the bulk ground material, and subsequent compounding of the desired materials in an intermeshing, co-rotating, twin screw extruder. Tensile and Izod impact tests were performed on the immiscible blends, whereas SEM and AFM analyzed the fracture surfaces. Dynamic mechanical thermal analysis show how thermal properties of the blends change as a function of blend composition. A polyolefin elastomer (PE) was incorporated into the blend and was shown to improve impact properties.
Novel Controlled Drug Release Biodegradable Polymers Systems
Biodegradable polymers, in particular polylactide and polyglycolide systems, having started out predominantly in the degradable sutures market, are now finding increasing use for controlled drug delivery and tissue engineering, where their use as temporary substrates or devices provides significant therapeutic advantages. The idea of using them as micro particles to prolong delivery of drugs have already been commercialized. This paper describes some work focusing on using these polymers as novel structures for localized and multiple drug delivery. The development of a dual drug eluting stent will be described to treat stenosis of coronary blood vessels, pulmonary airways or urological passages. The stents are inserted non invasively into and anchored to be resident in the body for a prescribed period to release drugs according to a prescribed profile and bio-erosion rate, hence eliminating the need for a second surgical procedure. Another application presented is the development of novel copolymers of PLA particles with stealth ability to evade the immune system and hence achieve protracted blood lifetimes, allowing efficacious therapy in especially cancer treatment. With suitable modifications, such nanoparticles may also be made to act as non-viral gene vectors to be used in delivering gene payloads to the nucleus.
Oxidative Resistance of Sulfone Polymers to Chlorinated Potable Water
Environmental factors are known to significantly impact the oxidative failure mechanism of plastics. The chlorine present in potable water as a disinfectant is an oxidant and has been shown to be able to significantly affect the failure mechanism of materials in potable water applications. In this paper, the impact of chlorinated potable water on four polysulfone materials was examined (PSU, PPSU/PSU blend, PPSU and glass-reinforced PSU). The materials were tested in the form of standard commercial insert fittings for plastic piping applications and exposed to continuously flowing aggressive chlorinated potable water at elevated temperature and pressure. The exposure period was chosen as twice the lifetime of the adjoining cross-linked polyethylene pipe (PEX) at the test condition. The exposure is shown not to have impacted the mechanical strength of the fittings when compared to the application pipe. Degradation, attributed to oxidation, of the exposed surface was observed. The morphological and chemical changes were examined using SEM, EDX and EDS. The differences between materials are presented. All materials were found to have excellent oxidative resistance to the chlorinated potable water at the tested condition. The PPSU material is seen to be the most resistant while the PSU materials the least resistant. The PPSU/PSU blend resistance was seen to be between that of the PPSU and PSU materials.
Photo Degradation Mechanisms of Layered Silicates Polymethyl Methacrylate Nanocomposites
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 (ie. 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 (1-4) will eventually comprise the original integrity of the materials’ desired properties. The focus of our research is to exploit nano-technology through incorporation of layered silicates for property enhancement.In this study, the impact of accelerated weathering upon newly developed polymethyl methacrylate-layered silicate nanocomposites materials was investigated. The silicate loading varied from 0 - 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 acrlyate linkages undergo a scission reaction upon UV exposure thereby compromising the original properties of the material. Furthermore, these scissions produce a yellowing of the polymer matrix which can inhibit its use where optical clarity in important.
Poly (Lactic-Glycolic Acid) and Funtional Hydrogels for Drug Delivery Applications
Biodegradable polyesters like poly(lactide-coglycolide acid) (PLGA) and pH-sensitive hydrogels have been used increasingly for various medical and biological applications. The present work focused on the use of these functional polymers to design an assembled drug delivery system (DDS) that could integrate multiple functions in a single device and achieve different release patterns. For PLGA, The major concerns are the poor hydrophilicity, accumulated acidity during degradation, and bulk erosion characteristics. In this study, poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEOPPO- PEO) tri-block copolymer and a nano-clay Cloisite® 30B were utilized as modifiers to control the degradation behavior and hydrophilicity of PLGA. For comparison, a block copolymer, poly(lactic acid)/ poly(ethylene glycol) (PLA-co-PEG) was synthesized. A pH-sensitive hydrogel together with a poly(hydroxyethyl methacrylate) (HEMA) was used as a gate to control drug release. By using this bilayered self-folding design, the drug protection and selfregulated oscillatory release were demonstrated.
Poly(Lactide); Moisture Sorption Characteristics and Storage Consequences
The attractiveness of high molecular mass poly(lactide), PLA, as a packaging material has increased in the last few years due to its natural biodegradability. PLA is a thermoplastic and compostable polymer produced from annually renewable resources, which can be totally degraded in aerobic or anaerobic environments in six months to five years. As PLA is now potentially available for use as food packaging polymeric material, one of the main concerns is to evaluate its durability with respect to the product shelf life. Since moisture sorption isotherms of polymeric materials are one of the controlling factors in the preservation of moisture-sensitive products, the aim of this research was to study the moisture-sorption characteristics of two poly(lactide) polymers at 5, 23, and 40°C for water activities (aw) from 0.1 to 0.9 as a function of short time storage. The PLA films were stored for one month at the same temperatures, and the glass transition and melting temperatures were monitored by Differential Scanning Calorimetry every week. It was found that PLA films absorb very low amounts of water, and the variation of the glass transition temperature as a function of time was statistically significant (P<0.05).
Polymeric Electrolyte Membrane (PEM) Nanocomposites for Fuel Cells via Direct Polycondesation
Polymeric electrolyte membrane (PEM) based fuel cell systems for automobiles, homes, and portable power fuel cells are already important for high energy density and very good environmentally benign energy sources . Currently, film forming fluorinated sulfonic acid containing copolymers are utilized primarily at 80C or lower for cost insensitive applications, such as the NASA space program. An increase in the fuel cell utilization temperature is desired for a number of reasons, including better efficiency and to improve the tolerance to impurities in fuels derived from H2, methanol, natural gas, biomass or reformed gasoline, such as carbon monoxide. New and improved mechanisms for conductivity above the boiling point of water are needed, which operate with little or no water. We have been interested in the direct copolymerization of sulfonic acid containing monomers to afford ion conducting systems such as poly (arylene ethers), including sulfones and ketones, and naphthalene dianhydride 6 membered ring based polyimides. Both random (statistical) copolymers and block copolymers based on these two major classes of materials are being investigated [2-7]. Several of these systems are surprisingly highly compatible with important additives, e.g., heteropoly acids (HPA), such as phosphotungstic acid, and zirconium hydrogen phosphate, which have potential for allowing conductivity above 100C. Highly dispersed nanocomposites have been achieved, which are possible because of specific interactions between the inorganic additive and the host copolymer, including hydrogen bonding, and dipolar interactions between the HPA and the sulfonic acid groups and/or backbone functionality. That highly dispersed HPA systems have been achieved can be demonstrated by FE-SEM, AFM and water extraction studies, and the fact that conductivity values of >0.1 S/cm are possible at temperatures approaching 140C. Excellent adhesion of the HPA to the matrix affords transparent mechanically robust
Rapid Surface Treatment of Reinforcing Fibers Using Ultraviolet Light Processing
A fast, inexpensive and environmentally benign process requiring only UV light and air for the surface treatment (oxidation) of reinforcing fibers has been developed that represents a substantial improvement over existing methods. In this new method, fibers are subjected to short wavelength ultraviolet (UV) light producing ozone from atmospheric oxygen. UV photons can also react with ozone to create monatomic oxygen, a highly reactive chemical species which is available to oxidize the fibers. Additionally, the UV photons can break chemical bonds on the fiber surface creating favorable conditions for reaction with ozone and monatomic oxygen. The result of this two-fold process is the rapid oxidation of the fiber surface that is essential to promote favorable interactions with the matrix in polymer composites. The effect of UVO treatment on the surface chemistry, tensile strength, and interfacial adhesion of a PAN based carbon fiber and an aramid fiber is reported.
Reactive Process for Recycling of Cellular Phone Housing
The front cover of cellular phone housing collected was grounded to be as the same size as the original particles before use, using knife mill. The unprinted glass fiber reinforced epoxy circuit boards were size reduced and pulverized using knife mill and hammer mill. The separated epoxy powder and glycidyl methacrylate (GMA) were added as the additive and the reactive species for reactive process using the batch mixer and the twin screw extruder. Izod impact strength at various temperatures, tensile test, particle size distribution analyses for the ground circuit board, SEM on the fracture surface, and dynamic mechanical spectroscopy were performed to characterize the reactive alloys and mixtures compounded by the batch mixer and the twin screw extruder.
Reactive Process for Recycling of Cellular Phone Housing
The front cover of the cellular phone housing was ground to be as the same size as the original particles before use using the knife mill and the undesired materials were separated with the sink-float process in water and salt. The unprinted glass fiber reinforced epoxy circuit boards were size reduced and pulverized using both the knife mill and the hammer mill. The separated epoxy powder and glycidyl methacrylate (GMA) were added as the additive and the reactive species for the reactive process using the batch mixer and the twin screw extruder, respectively. Izod impact strength at various temperatures, tensile test, particle size distribution analysis for the ground circuit board, SEM on the fracture surface, and dynamic mechanical spectroscopy were performed to characterize the reactive polymer alloys and mixtures compounded by the batch mixer and the twin screw extruder.
Recycleability of Polymer-Clay Nanocomposites: Part 1 - The Influence of Multiple-Extrusions on Structure and Mechanical Properties
The effects of multiple-extrusions, up to eleven cycles, on the structure and properties of virgin and nanoclay-filled nylon-12 were investigated. X-ray diffraction and transmission electron microscopy studies showed that the degree of clay exfoliation improves with each successive extrusion sequence up to the seventh cycle. The impact strength of the nanocomposites were enhanced while that of the virgin nylon-12 deteriorated. Regrinding of the nanocomposite resin prior to subsequent extrusion was shown to further improve the clay exfoliation and mechanical performance.
Recycleability of Polymer-Clay Nanocomposites: Part 2 - The Influence of Multiple-Extrusions on Thermal and Rheological Properties
Nylon-12 and nylon-12/clay nanocomposite were recycled by up to eleven times using the melt-extrusion process. Changes in thermal and rheological properties were investigated using DMTA, DSC, TGA, and capillary rheometry techniques. Both materials showed a gradual decrease in phase transition temperatures and storage modulus following repeated extrusions. In addition, the materials melt viscosity increased in response to successive reprocessing. Relative to the nylon-12, the melt viscosity of nanocomposites was reduced by more than 20% and their glass transition temperature was elevated by about 2.0 to 6.5degC depending on the number of extrusion cycles.
Recycled Newspaper and Chicken Feathers as Reinforcement Fiber in Bio-Composite Materials
Nonwoven mats of cellulose and keratin fiber were manufactured from recycled kraft paper, newspaper, and processed chicken feathers using a wetlay process. Hybrid fiber mats were produced by mixing different ratios of the three fiber types together in the wetlay process. Composite materials were manufactured by infiltrating these mats with an acrylated epoxidized soybean oil- (AESO) based resin using vacuum assisted resin transfer molding (VARTM). The room temperature cured composite panels contained between 16 and 25% by weight fiber depending on the original mat structure. The fiber mats contained 0 to 50 wt% recycled milled newspaper, 40 to 100 wt% pulp fiber recycled from kraft paper and 0 to 60 wt% cleaned and chopped feathers. These composites are low cost, environmentally friendly, derived from renewable resources, energy efficient, and could be used in many applications such as civil infrastructure, automotive and trucking, temporary roadway matting.
Reducing Paint Particle Size for Painted TPO Regrind
Many industries, such as the automotive industry, are faced with a high volume of plastics scrap associated with painted plastic parts. Ideally, the paint is removed prior to reuse of the painted regrind. Paint removal methods include differential thermal expansion, chemical attack and abrasion. If not removed, paint flakes in the regrind material influence the mechanical properties and aesthetics of the product molded from the painted regrind. The size of the paint flakes will likely have an influence on the mechanical properties of the molded part.A reground painted thermoplastic olefin (TPO) will be extruded using a general purpose and a “grater” screw being developed at UML. The grater section design will then be modified to implement a progressive grating technique. The effect of the design change on paint flake size, output, melt temperature and mechanical properties will be monitored.
Solid Phase Graft Copolymerization of PE-g-MA
The solid phase graft copolymerization method was used to graft maleic anhydride onto commercial polyethylenes. This process is environmentally friendly since it requires minimal recovery or no use of solvent and the process conditions are mild. NMR analysis confirms the successful grafting of maleic anhydride onto the backbones of both linear low-density polyethylene (LLDPE) and ultra high molecular weight polyethylene (UHMWPE). Graft levels for all the polymers were quantified by FTIR absorbance as well as wet-chemical titration. Significant processing parameters were identified based on statistical design of experiments.
Static Charging Methods and Graphic Material Properties for Low Scrap In-Mold Decoration
The use of static charging techniques has been investigated to understand which methods produce the most highly repeatable results for in-mold decoration. The techniques studied were the direct and remote charging methods.In addition to charging methods, the study evaluated material properties, gate location and environmental conditions that contribute to the success and repeatability of in-mold decoration.The optimal method, environmental conditions and material properties were found that produce low scrap results. Conclusions were made regarding optimal charging methods and graphic label constructions.
Strength, Toughness, Lifetime and Reliability of Plastics in Engineering Applications
Major factors affecting short term and longterm performance of plastics in engineering applications include a) chemical makeup and molecular architecture, additives etc; b) material and parts manufacturing conditions; c) installation and service conditions that include load, loading rate, temperature and other environmental conditions. Successful design of plastic components for intended application requires an understanding of the role of the above factors together with economic considerations that account for a cost of fabrication as well as for a price of failure. Material characterization and ranking with respect to strength, toughness and durability provide a basis for rational design with plastics. There are industrial standards and regulations develop to assist in product selection. Advantages and limitations of widely publicized standards and methods for durability and lifetime of engineering thermoplastics will be illustrated by examples of field failure analysis. Methodology of material durability and structural reliability assessment will be discussed.
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