89 Matching Results

Search Results

Advanced search parameters have been applied.

Assessing the benefits of design for recycling for plastics inelectronics: A case study of computer enclosures

Description: With the emergence of extended producer responsibilityregulations for electronic devices, it is becoming increasingly importantfor electronics manufacturers to apply design for recycling (DFR) methodsin the design of plastic enclosures. This paper presents an analyticalframework for quantifying the environmental and economic benefits of DFRfor plastic computer enclosures during the design process, usingstraightforward metrics that can be aligned with corporate environmentaland financial performance goals. The analytical framework is demonstratedvia a case study of a generic desktop computer enclosure design, which isrecycled using a typical US "take-back" system for plastics from wasteelectronics. The case study illustrates how the analytical framework canbe used by the enclosure designer to quantify the environmental andeconomic benefits of two important DFR strategies: choosing high-valueresins and minimizing enclosure disassembly time. Uncertainty analysis isperformed to quantify the uncertainty surrounding economic conditions inthe future when the enclosure is ultimately recycled.
Date: December 31, 2007
Creator: Masanet, Eric & Horvath, Arpad
Partner: UNT Libraries Government Documents Department

Advanced Thermoplastic Materials for District Heating Piping Systems

Description: The work described in this report represents research conducted in the first year of a three-year program to assess, characterize, and design thermoplastic piping for use in elevated-temperature district heating (DH) systems. The present report describes the results of a program to assess the potential usefulness of advanced thermoplastics as piping materials for use in DH systems.
Date: April 1988
Creator: Raske, D. T. & Karvelas, D. E.
Partner: UNT Libraries Government Documents Department

Application of Plastic Bags and Sheeting for Operation and Maintenance Across a Contamination Barrier

Description: The following document describes the usage of Vinylite or plastic sheeting for operation and maintenance across a contamination barrier, presenting ecological advantages, photos of special equipment and techniques used during procedure, and the purpose of eliminating open air transfer in contaminated area.
Date: 1952
Creator: Moulthrop, H. A.
Partner: UNT Libraries Government Documents Department

Definition of Brittleness: Connections Between Mechanical and Tribological Properties of Polymers.

Description: The increasing use of polymer-based materials (PBMs) across all types of industry has not been matched by sufficient improvements in understanding of polymer tribology: friction, wear, and lubrication. Further, viscoelasticity of PBMs complicates characterization of their behavior. Using data from micro-scratch testing, it was determined that viscoelastic recovery (healing) in sliding wear is independent of the indenter force within a defined range of load values. Strain hardening in sliding wear was observed for all materials-including polymers and composites with a wide variety of chemical structures-with the exception of polystyrene (PS). The healing in sliding wear was connected to free volume in polymers by using pressure-volume-temperature (P-V-T) results and the Hartmann equation of state. A linear relationship was found for all polymers studied with again the exception of PS. The exceptional behavior of PS has been attributed qualitatively to brittleness. In pursuit of a precise description of such, a quantitative definition of brittleness has been defined in terms of the elongation at break and storage modulus-a combination of parameters derived from both static and dynamic mechanical testing. Furthermore, a relationship between sliding wear recovery and brittleness for all PBMs including PS is demonstrated. The definition of brittleness may be used as a design criterion in selecting PBMs for specific applications, while the connection to free volume improves also predictability of wear behavior.
Date: August 2008
Creator: Hagg Lobland, Haley E.
Partner: UNT Libraries

Assessment of Current Process Modeling Approaches to Determine Their Limitations, Applicability and Developments Needed for Long-Fiber Thermoplastic Injection Molded Composites

Description: This report describes the status of the current process modeling approaches to predict the behavior and flow of fiber-filled thermoplastics under injection molding conditions. Previously, models have been developed to simulate the injection molding of short-fiber thermoplastics, and an as-formed composite part or component can then be predicted that contains a microstructure resulting from the constituents’ material properties and characteristics as well as the processing parameters. Our objective is to assess these models in order to determine their capabilities and limitations, and the developments needed for long-fiber injection-molded thermoplastics (LFTs). First, the concentration regimes are summarized to facilitate the understanding of different types of fiber-fiber interaction that can occur for a given fiber volume fraction. After the formulation of the fiber suspension flow problem and the simplification leading to the Hele-Shaw approach, the interaction mechanisms are discussed. Next, the establishment of the rheological constitutive equation is presented that reflects the coupled flow/orientation nature. The decoupled flow/orientation approach is also discussed which constitutes a good simplification for many applications involving flows in thin cavities. Finally, before outlining the necessary developments for LFTs, some applications of the current orientation model and the so-called modified Folgar-Tucker model are illustrated through the fiber orientation predictions for selected LFT samples.
Date: November 30, 2006
Creator: Nguyen, Ba Nghiep; Holbery, Jim; Smith, Mark T.; Kunc, Vlastimil; Norris, Robert E.; Phelps, Jay et al.
Partner: UNT Libraries Government Documents Department

Initial inclusion of thermodynamic considerations in Kayenta.

Description: A persistent challenge in simulating damage of natural geological materials, as well as rock-like engineered materials, is the development of efficient and accurate constitutive models. The common feature for these brittle and quasi-brittle materials are the presence of flaws such as porosity and network of microcracks. The desired models need to be able to predict the material responses over a wide range of porosities and strain rate. Kayenta (formerly called the Sandia GeoModel) is a unified general-purpose constitutive model that strikes a balance between first-principles micromechanics and phenomenological or semi-empirical modeling strategies. However, despite its sophistication and ability to reduce to several classical plasticity theories, Kayenta is incapable of modeling deformation of ductile materials in which deformation is dominated by dislocation generation and movement which can lead to significant heating. This stems from Kayenta's roots as a geological model, where heating due to inelastic deformation is often neglected or presumed to be incorporated implicitly through the elastic moduli. The sophistication of Kayenta and its large set of extensive features, however, make Kayenta an attractive candidate model to which thermal effects can be added. This report outlines the initial work in doing just that, extending the capabilities of Kayenta to include deformation of ductile materials, for which thermal effects cannot be neglected. Thermal effects are included based on an assumption of adiabatic loading by computing the bulk and thermal responses of the material with the Kerley Mie-Grueneisen equation of state and adjusting the yield surface according to the updated thermal state. This new version of Kayenta, referred to as Thermo-Kayenta throughout this report, is capable of reducing to classical Johnson-Cook plasticity in special case single element simulations and has been used to obtain reasonable results in more complicated Taylor impact simulations in LS-Dyna. Despite these successes, however, Thermo-Kayenta requires additional refinement ...
Date: July 1, 2010
Creator: Brannon, Rebecca Moss (University of Utah, Salt Lake City, UT); Bishop, Joseph E.; Fuller, Timothy J. (University of Utah, Salt Lake City, UT) & Strack, Otto Eric
Partner: UNT Libraries Government Documents Department

High-resolution optical imaging on thermoplastic film

Description: Experimental details of a novel method for recording optical images is presented. In this method, a photoconductive layer arranges electric charges according to the optical image projected onto it. The differential electric fields thus produced, squeeze a thermoplastic layer into ridges that constitute the final image. The interference of two laser beams (0.83 mu m) that formed an optical image of l000 cycles/mm was clearly and accurately recorded. The spatial frequency response differs from the conventional photographic method and is well suited for holograms. The image can be erased and the medium reused many times. The thermoplastic layer alone can be written on'' by charges applied by touching with a thin wire. (auth)
Date: November 16, 1973
Creator: Chambers, E. S.; Hsieh, H. J.; Lee, E. L. & Boogaard, J. J.
Partner: UNT Libraries Government Documents Department

Functionalized Materials From Elastomers to High Performance Thermoplastics

Description: Synthesis and incorporation of functionalized materials continues to generate significant research interest in academia and in industry. If chosen correctly, a functional group when incorporated into a polymer can deliver enhanced properties, such as adhesion, water solubility, thermal stability, etc. The utility of these new materials has been demonstrated in drug-delivery systems, coatings, membranes and compatibilizers. Two approaches exist to functionalize a material. The desired moiety can be added to the monomer either before or after polymerization. The polymers used range from low glass transition temperature elastomers to high glass transition temperature, high performance materials. One industrial example of the first approach is the synthesis of Teflon(reg. sign). Poly(tetrafluoroethylene) (PTFE or Teflon(reg. sign)) is synthesized from tetrafluoroethylene, a functionalized monomer. The resulting material has significant property differences from the parent, poly(ethylene). Due to the fluorine in the polymer, PTFE has excellent solvent and heat resistance, a low surface energy and a low coefficient of friction. This allows the material to be used in high temperature applications where the surface needs to be nonabrasive and nonstick. This material has a wide spread use in the cooking industry because it allows for ease of cooking and cleaning as a nonstick coating on cookware. One of the best examples of the second approach, functionalization after polymerization, is the vulcanization process used to make tires. Natural rubber (from the Hevea brasiliensis) has a very low glass transition temperature, is very tacky and would not be useful to make tires without synthetic alteration. Goodyear's invention was the vulcanization of polyisoprene by crosslinking the material with sulfur to create a rubber that was tough enough to withstand the elements of weather and road conditions. Due to the development of polymerization techniques to make cis-polyisoprene, natural rubber is no longer needed for the manufacturing of tires, but ...
Date: May 31, 2003
Creator: Salazar, Laura Ann
Partner: UNT Libraries Government Documents Department

Encapsulation of explosive particles by parylene. Quarterly report, October--December, 1971

Description: Parylene is the generic name for members, e.g. parylene N,C,D of a thermoplastic polymer series developed by Union Carbide (Reta is a trade name for the materials). All of the members are laid down by a vacuum, vapor deposition process. The properties and uses for each member of the series differ from each other, but collectively the Parylenes have a wide range of applications. Gas permeability and moisture vapor transmission of Parylene C are very low. These properties make Parylene potentially very useful with or near explosives or components. One of the forms, Parylene C--the monomer of dichloro-di-p-xyly-lene--is potentially attractive. Its density is 1.29 g/cc. In this study the initial emphasis will be on the feasibility of coating HE particles. Substrates of diminishing particle size will be encapsulated to establish the particle-size limitation of the process.
Date: December 31, 1972
Creator: Sandoval, J.
Partner: UNT Libraries Government Documents Department

Molecular-To-Continuum Fracture Analysis of Thermosetting Polymer/Solid Interfaces

Description: This report focuses on the relationship between the fundamental interactions acting across an interface and macroscopic engineering observable such as fracture toughness or fracture stress. The work encompasses experiment, theory, and simulation. The model experimental system is epoxy on polished silicon. The interfacial interactions between the substrate and the adhesive are varied continuously using self-assembling monolayer. Fracture is studied in two specimen geometries: a napkin-ring torsion geometry and a double cantilevered beam specimen. Analysis and modeling involves molecular dynamics simulations and continuum mechanics calculations. Further insight is gained from analysis of measurements in the literature of direct force measurements for various fundamental interactions. In the napkin-ring test, the data indicate a nonlinear relationship between interface strength and fracture stress. In particular, there is an abrupt transition in fracture stress which corresponds to an adhesive-to-cohesive transition. Such nonlinearity is not present in the MD simulations on the tens-of-nanometer scale, which suggests that the nonlinearity comes from bulk material deformation occurring on much larger length scales. We postulate that the transition occurs when the interface strength becomes comparable to the yield stress of the material. This postulate is supported by variation observed in the fracture stress curve with test temperature. Detailed modeling of the stress within the sample has not yet been attempted. In the DCB test, the relationship between interface strength and fracture toughness is also nonlinear, but the fracture mechanisms are quite different. The fracture does not transition from adhesive to cohesive, but remains adhesive over the entire range of interface strength. This specimen is modeled quantitatively by combining (i) continuum calculations relating fracture toughness to the stress at 90 {angstrom} from the crack tip, and (ii) a relationship from molecular simulations between fracture stress on a {approx} 90 {angstrom} scale and the fraction of surface sites which chemically bond. ...
Date: January 1, 2000
Creator: KENT,MICHAEL S.; REEDY JR.,EARL DAVID & STEVENS,MARK J.
Partner: UNT Libraries Government Documents Department

Characterization of polyxylylenes with solid state {sup 13}C nuclear magnetic resonance spectroscopy

Description: Polyxylylenes are thermoplastics used as encapsulants for electronic devices. Five polyxylylenes were prepared by pyrolysis of [2.2]paracyclophanes and characterized by solid state {sup 13}C NMR spectroscopy. The chemical shift data, in combination with interrupted decoupling experiments, allowed assignment of resonances to their carbon sources in the polymers. This confirmed the integrity of the xylylene building block in the polymers and is consistent with linear polymers. No crosslinking could be detected within the NMR sensitivity limits. Residual paracyclophane was detected by {sup 13}C CP MAS NMR spectroscopy in the polyxylylene samples prepared at room temperature; however discrete {sup 13}C resonances due to amorphous and crystalline phases in the polymers were not resolved.
Date: February 1, 1996
Creator: Loy, D.A.; Assink, R.A.; Jamison, G.M.; McNamara, W.F.; Schneider, D.A. & Prabakar, S.
Partner: UNT Libraries Government Documents Department

Analysis of Thermoplastic Polyimide + Polymer Liquid Crystal Blends

Description: Thermoplastic polyimides (TPIs) exhibit high glass transition temperatures (Tgs), which make them useful in high performance applications. Amorphous and semicrystalline TPIs show sub-Tg relaxations, which can aid in improving strength characteristics through energy absorption. The a relaxation of both types of TPIs indicates a cooperative nature. The semicrystalline TPI shows thermo-irreversible cold crystallization phenomenon. The polymer liquid crystal (PLC) used in the blends is thermotropic and with longitudinal molecular structure. The small heat capacity change (ACP) associated with the glass transition indicates the PLC to be rigid rod in nature. The PLC shows a small endotherm associated with the melting. The addition of PLC to the semicrystalline TPI does not significantly affect the Tg or the melting point (Tm). The cold crystallization temperature (Tc) increases with the addition of the PLC, indicating channeling phenomenon. The addition of PLC also causes a negative deviation of the ACP, which is another evidence for channeling. The TPI, PLC and their blends show high thermal stability. The semicrystalline TPI absorbs moisture; this effect decreases with the addition of the PLC. The absorbed moisture does not show any effect on the degradation. The addition of PLC beyond 30 wt.% does not result in an improvement of properties. The amorphous TPI + PLC blends also show the negative deviation of ACP from linearity with composition. The addition of PLC causes a decrease in the thermal conductivity in the transverse direction to the PLC orientation. The thermomechanical analysis indicates isotropic expansivity for the amorphous TPI and a small anisotropy for the semicrystalline TPI. The PLC shows large anisotropy in expansivity. Even 5 wt. % concentration of PLC in the blend induces considerable anisotropy in the expansivity. Thus, blends show controllable expansivity through PLC concentration. Amorphous TPI + PLC blends also show excellent film formability. The amorphous TPI ...
Date: May 1998
Creator: Gopalanarayanan, Bhaskar
Partner: UNT Libraries

Formulation of Molding Materials From Recycled Printed Wiring Boards

Description: The objective of this project was to formulate the pulverized electronic waste (PEW) stream derived from grinding obsolete electronic assemblies and combine this material with thermoplastic or thermosetting polymers into useful, high-value commercial products materials. PEW consists primarily of various thermoset plastic materials and glass fibers from the printed wiring boards, along with ceramic pieces from chip carriers and other electronic components. Typically, the thermosetting materials have the same desirable properties as in the original electronic assembly, including relatively high temperature resistance, excellent chemical resistance, and flame retardancy. These properties combine to make PEW an inherently good inert filler material for plastic composites.
Date: April 20, 1998
Creator: Lula, J.W. & Bohnert, G.W.
Partner: UNT Libraries Government Documents Department

Electro-Microfluidic Packaging

Description: Electro-microfluidics is experiencing explosive growth in new product developments. There are many commercial applications for electro-microfluidic devices such as chemical sensors, biological sensors, and drop ejectors for both printing and chemical analysis. The number of silicon surface micromachined electro-microfluidic products is likely to increase. Manufacturing efficiency and integration of microfluidics with electronics will become important. Surface micromachined microfluidic devices are manufactured with the same tools as IC's (integrated circuits) and their fabrication can be incorporated into the IC fabrication process. In order to realize applications for devices must be developed. An Electro-Microfluidic Dual In-line Package (EMDIP{trademark}) was developed surface micromachined electro-microfluidic devices, a practical method for getting fluid into these to be a standard solution that allows for both the electrical and the fluidic connections needed to operate a great variety of electro-microfluidic devices. The EMDIP{trademark} includes a fan-out manifold that, on one side, mates directly with the 200 micron diameter Bosch etched holes found on the device, and, on the other side, mates to lager 1 mm diameter holes. To minimize cost the EMDIP{trademark} can be injection molded in a great variety of thermoplastics which also serve to optimize fluid compatibility. The EMDIP{trademark} plugs directly into a fluidic printed wiring board using a standard dual in-line package pattern for the electrical connections and having a grid of multiple 1 mm diameter fluidic connections to mate to the underside of the EMDIP{trademark}.
Date: June 1, 2002
Creator: BENAVIDES, GILBERT L. & GALAMBOS, PAUL C.
Partner: UNT Libraries Government Documents Department

Creep in Photovoltaic Modules: Examining the Stability of Polymeric Materials and Components

Description: Interest in renewable energy has motivated the implementation of new polymeric materials in photovoltaic modules. Some of these are non-cross-linked thermoplastics, in which there is a potential for new behaviors to occur, including phase transformation and visco-elastic flow. Differential scanning calorimetry and rheometry data were obtained and then combined with existing site-specific time-temperature information in a theoretical analysis to estimate the displacement expected to occur during module service life. The analysis identified that, depending on the installation location, module configuration and/or mounting configuration, some of the thermoplastics are expected to undergo unacceptable physical displacement. While the examples here focus on encapsulation materials, the concerns apply equally to the frame, junction-box, and mounting-adhesive technologies.
Date: February 1, 2011
Creator: Miller, D. C.; Kempe, M. D.; Glick, S. H. & Kurtz, S. R.
Partner: UNT Libraries Government Documents Department

Final Report: Interphase Analysis and Control in Fiber Reinforced Thermoplastic Composites

Description: This research program builds upon a multi-disciplinary effort in interphase analysis and control in thermoplastic matrix polymer matrix composites (PMC). The research investigates model systems deemed of interest by members of the Automotive Composites Consortium (ACC) as well as samples at the forefront of PMC process development (DRIFT and P4 technologies). Finally, the research investigates, based upon the fundamental understanding of the interphases created during the fabrication of thermoplastic PMCs, the role the interphase play in key bulk properties of interest to the automotive industry.
Date: March 14, 2009
Creator: Kellar, Jon J.; Cross, William M. & Kjerengtroen, Lidvin
Partner: UNT Libraries Government Documents Department

A REVIEW OF THE MEASUREMENT AND DEVELOPMENT OF CRYSTALLINITY AND ITS RELATION TO PROPERTIES IN NEAT POLY(PHENYLENE SULFIDE) AND ITS FIBER REINFORCED COMPOSITES

Description: This literature review paper was prepared for the Department of Energy Automotive Lightweighting Program to address materials interest expressed by the Automotive Composites Consortium and it summarizes the measurement and development of crystallinity and its relation to properties in poly(phenylene sulfide) (PPS) and its fiber reinforced composites. The objective of this effort was to broaden the understanding of low-cost, semi-crystalline thermoplastic resins and composites for use in potential future automotive applications. PPS has an excellent combination of attributes including good mechanical properties and thermal stability, high chemical resistance, low moisture absorption, good weathering resistance, high dimensional stability, low flammability, and excellent processability. Specific areas addressed in this report include: Structure of PPS; Techniques for measuring crystallinity; Crystallinity as a function of prior treatment; Crystallization kinetics and morphology; Effect of variation of crystallinity on properties of PPS and its composites; Environmental stability; Unusual effects of cooling rates and degree of crystallinity on mechanical properties of AS4/PPS composites; Recent PPS laminate data (Ten Cate Advanced Composites); and Recommendations for future research.
Date: January 31, 2005
Creator: Spruiell, J.E.
Partner: UNT Libraries Government Documents Department

STUDY OF ACTIVATION OF COAL CHAR

Description: This is the first report on a project whose aim is to explore in a fundamental manner the factors that influence the development of porosity in coal chars during the process of activation. It is known that choices of starting coal, activating agent and conditions can strongly influence the nature of an activated carbon produced from a coal. In this initial study, the basic techniques for producing the char (via slow pyrolysis in inert gas) and characterizing it (using nitrogen gas adsorption) are developed. The stark differences between the chars that can be produced from Beulah-Zap lignite and Pittsburgh No. 8 bituminous coal are presented. The former is a thermoset material, and gives an easily activated char, whereas the former is thermoplastic and produces during pyrolysis a low porosity char that is difficult to activate.
Date: July 1, 2003
Creator: Suuberg, E.M.
Partner: UNT Libraries Government Documents Department

Failure Plane Orientations for Fiber Composites

Description: Using a recently developed failure theory for transversely isotropic fiber composites, it is shown how the orientation of the failure surface can be determined for transverse tension and compression. Experimental data on failure surface orientations have been obtained for four carbon fiber composite systems based on both thermoplastic and thermosetting matrix materials. Average compression failure planes for the different composite materials were measured to range from 31{sup o} to 38{sup o} from the load axis. Reasonable agreement was obtained between these measured angles and those predicted from application of the new failure theory.
Date: July 12, 2002
Creator: Christensen, R. M. & DeTeresa, S. J.
Partner: UNT Libraries Government Documents Department

Free form fabrication of thermoplastic composites

Description: This report describes the results of composites fabrication research sponsored by the Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories. They have developed, prototyped, and demonstrated the feasibility of a novel robotic technique for rapid fabrication of composite structures. Its chief innovation is that, unlike all other available fabrication methods, it does not require a mold. Instead, the structure is built patch by patch, using a rapidly reconfigurable forming surface, and a robot to position the evolving part. Both of these components are programmable, so only the control software needs to be changed to produce a new shape. Hence it should be possible to automatically program the system to produce a shape directly from an electronic model of it. It is therefore likely that the method will enable faster and less expensive fabrication of composites.
Date: February 1, 1998
Creator: Kaufman, S.G.; Spletzer, B.L. & Guess, T.R.
Partner: UNT Libraries Government Documents Department

Thermoplastic encapsulation of waste surrogates by high-shear mixing

Description: Brookhaven National Laboratory (BNL) has developed a robust, extrusion-based polyethylene encapsulation process applicable to a wide range of solid and aqueous low-level radioactive, hazardous and mixed wastes. However, due to the broad range of physical and chemical properties of waste materials, pretreatment of these wastes is often required to make them amenable to processing with polyethylene. As part of the scope of work identified in FY95 {open_quotes}Removal and Encapsulation of Heavy Metals from Ground Water,{close_quotes} EPA SERDP No. 387, that specifies a review of potential thermoplastic processing techniques, and in order to investigate possible pretreatment alternatives, BNL conducted a vendor test of the Draiswerke Gelimat (thermokinetic) mixer on April 25, 1995 at their test facility in Mahwah, NJ. The Gelimat is a batch operated, high-shear, high-intensity fluxing mixer that is often used for mixing various materials and specifically in the plastics industry for compounding additives such as stabilizers and/or colorants with polymers.
Date: December 1, 1995
Creator: Lageraaen, P.R.; Kalb, P.D. & Patel, B.R.
Partner: UNT Libraries Government Documents Department

Treatability study on the use of by-product sulfur in Kazakhstan for the stabilization of hazardous and radioactive wastes

Description: The Republic of Kazakhstan generates significant quantities of excess sulfur from the production and refining of petroleum reserves. In addition, the country also produces hazardous, and radioactive wastes which require treatment/stabilization. In an effort to find secondary uses for the elemental sulfur, and simultaneously produce a material which could be used to encapsulate, and reduce the dispersion of harmful contaminants into the environment, BNL evaluated the use of the sulfur polymer cement (SPC) produced from by-product sulfur in Kazakhstan. This thermoplastic binder material forms a durable waste form with low leaching properties and is compatible with a wide range of waste types. Several hundred kilograms of Kazakhstan sulfur were shipped to the U.S. and converted to SPC (by reaction with 5 wt% organic modifiers) for use in this study. A phosphogypsum sand waste generated in Kazakhstan during the purification of phosphate fertilizer was selected for treatment. Waste loading of 40 wt% were easily achieved. Waste form performance testing included compressive strength, water immersion, and Accelerated Leach Testing. 14 refs., 7 figs., 6 tabs.
Date: August 1997
Creator: Yim, Sung Paal; Kalb, P. D. & Milian, L. W.
Partner: UNT Libraries Government Documents Department

Product formulations using recycled tire crumb rubber. Final report/project accomplishments summary

Description: The objective of this project was to combine crumb rubber and synthetic fiber obtained from scrap tires with thermoplastic polymers and convert these materials into commercially useful, high-value products. A specific goal was to use these materials for roofing, while remaining cognizance of other potential applications.
Date: February 1, 1998
Creator: Lula, J.W. & Bohnert, G.W.
Partner: UNT Libraries Government Documents Department