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.
Harnessing Natural Polymers and Fibers for the Development of Biocomposites
Economic and environmental forces are providing an impetus for the development of biocomposites from renewable agricultural byproducts. In pursuit of this goal, we are developing biocomposites from wheat-, kenaf-, and corn-byproducts without external additives. Our differential scanning calorimetry (DSC) measurements suggest that micronized wheat straw and inner kenaf fibers have similar thermal characteristics at 50°C < T < 400°C, thus they can be co-processed. The flexural strength of the composites formulated from micronized wheat straw and kenaf fibers increases as the concentration of straw in the composite increases. Postcuring the composites at 190°C also decreases the strength.
How to Present Expert Witness to Court
Lawyers and judges have, most of the time, little understanding about the mechanical, chemical and physical behavior of plastics. A selection of legal cases will be presented and it will be emphasized that presentation is sometimes rather an art than a science. This is illustrated by three examples of legal cases.1. Water storage tanks, consisting of an outer and an inner stainless steel tanks with insulation between the tanks. In order to prevent freezing of the wastewater a heating mat is adhered using silicon kit to the outside of the inner tank. PE tanks were ordered to substitute the expensive stainless steel tanks. The heating mats became overheated because of the poor adhesion to PE. It is rather easy to convince court that the bonding between silicon kit and PE is absent and that this is the reason that containers for silicon kit are of PE.2. Scratches on textured plastic panels. A supplier promised to manufacture panels of high surface quality, but was not able to meet the requirements and painted the panels. The supplier billed the customer for $ 400 000 and in court this claim was rejected on the basis of strict contractual liability. The lawyers even did not want to have the technical explanation, why the scratched occurred, in my failure report.3. Fatigue of flexible covers for cupboards made of ABS. The manufacturer of the cupboards covers specified ABS with a rubber content (polybutadiene) of 40 % to avoid fatigue of the covers that were subjected to bending during opening and closing of the cupboards. The covers often did to satisfy the surface gloss requirements and the manufacturer of the covers proposed ABS and PS with a lower polybutadiene content. These covers met the surface gloss requirements, but failed in surface due to the low polybutadiene content. This resulted in a loss of confidence of the Cupboard Company and almost resulted in a bankruptcy. The final solution was to use ABS from another supplier and stricter quality control.
Influence of Organo-Clay Type on the Thermal and Mechanical Properties of Poly(L-Lactide)/Clay Nanocomposites
Poly (l-lactide) (PLLA) has received considerable attention recently because it is environmentally friendly, derived from agricultural sources, and biodegradable. However, the mechanical properties of PLLA are typically low compared to other petroleum-based plastics. Recently, properties such as modulus and heat deflection temperature have been improved by creating polymer/clay nanocomposites. This study focuses on the effect of different organic modifiers for montmorrillonite clay on the thermal and mechanical properties of PLLA. Upon the addition of a small amount (1-10 wt %) of these modified clays, the storage modulus and Tg increases for all types of clays. The greatest increase in properties is found using quaternary ammonium ion having a pendant benzyl group.
Injection Molded Biocomposites from Natural Fibers and Modified Polyamide
This paper focuses on the development of a new technology and process in order to manufacture natural fiber reinforced engineering thermoplastics like nylon 6. Natural fibers are not suitable reinforcements when high temperature melting (above 200°C) engineering thermoplastics is used as matrix materials because natural fibers start to degrade thermally at above 200°C. Small quantities of inorganic salts like lithium chloride were added to the nylon 6 during melt extrusion processing to depress its melting temperature. The final composites are injection molded into test specimen at the reduced processing temperatures of nylon 6. The molded plastics and composites are tested for mechanical and thermal properties. Natural fiber reinforced nylon 6 composites show improved tensile and flexural properties. The morphology of the fracture surfaces is observed using Environmental Scanning Electron Microscopy.
Injection Molding of a Starch Based Polymer Reinforced with Natural Fibers
Biodegradable composites were developed by compounding a commercial corn starch polymer with pine and Alfa fibers on a counter-rotating twin screw extruder. Subsequently, the compounds were injection molded under optimized conditions and characterized for the respective mechanical behavior and morphological features.The obtained results establish by evidence that this kind of composites present mechanical performance (in terms of stiffness and strength) within the range of the polymeric systems based on high consumption thermoplastics. In comparison with pine fibers, Alfa based composites presented a better performance as result of various advantageous morphological and interfacial aspects.
Injection Molding of Polyetherimide Using Water Cooled Molds
Many injection molders when processing high temperature amorphous resins like Polyetherimide (PEI) use oil cooled molds to enhance the mold filling process and achieve the best mechanical properties attainable. The practice of molding with high mold temperatures is generally recommended by material suppliers in order to reduce molded-in stress, which can have a negative effect on final molded part performance. While it is still good molding practice to use oil cooled molds, there are many instances in which PEI can be molded into acceptable parts using water as the heat transfer fluid. Water cooled molds offer several advantages over oil and includes reducing environmental and personnel safety concerns in addition to lower capital cost and ease of operation.
Low Temperature Durable of Copolyester-Poycaprolactone- Hydroxypropylcellulose Biodegradable Blends
Pittsburg State University has worked on the development of biodegradable blends for low temperature, durable applications in bull castration clips for use in the farm industry. These clips are biocompatible, to ensure that meat is not contaminated. At the same time they also exhibit biodegradability and strength in temperatures as low as –20 °C; temperatures that can be experienced in the North American farm belt. The blends contained the following materials, Eastar Bio Copolymer, Polycaprolactone, Polyethylene glycol (Carbowax), Hydroxypropylcellulose (Klucel), Cornstarch, and Titanium Dioxide. Table 1 shows the ingredients of each blend. In vitro results show degradation of the samples from 5% to over 25% of its’ original mass over a 28- day period. Differential Scanning Calorimetry results showed the Tg of the blends reaching –24.15 °C, well below the targeted value of –20 °C.
Mechanical Properties of Carbonized Bamboo Fiber Reinforced Biodegradable Polymer Composite
The mechanical properties of biodegradable polymer composite with carbonized bamboo fibers were evaluated. Poly (butylene succinate) (PBS) was used as the biodegradable plastic matrix while the condition of carbonization was varied. By increasing fiber content, tensile modulus was confirmed to increase. In particular, the tensile modulus of composite filled with semi-carbonized bamboo displayed higher values than the uncarbonized bamboo fibers composite. The values of tensile strength decreased according to the increase of fiber content; however, the carbonized bamboo fiber composites experienced less decrease than the uncarbonized ones. The surface resistivity of carbonized bamboo fiber composites was lower than that of bamboo fibers and also decreased with the increase in fiber content in each case.
Mechanical Properties of Hybrid Polyester Composites
There are different reasons why the production of polyester composites with natural reinforcements, like jute can be of interest. One of them is to fabricate the hybrid composites with cheap waste jute sacks as reinforcements in combination with glass mat. The laminates have been fabricated with a different number of jute and glass mat layers and different type of polyester resins. Also, the content of cross-linking agent has been varied. As the indicator of change of mechanical properties, tensile and flexural strength as well as tensile and flexural modulus have been determined. Based on the planned experiments and statistical analysis it can be concluded that in comparison with glass mat polyester composites, the mechanical properties of hybrid composites in optimal combination of glass and jute reinforcements are lower, but at the same time the laminates are 15 to 20% cheaper.
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.
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