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Multiple melting peak analysis with gel-spun ultra-high molar mass polyethylene

Description: The multiple melting peaks observed on differential scanning calorimetry (DSC) of ultrahigh molar-mass PE fibers are analyzed as a function of sample mass. Using modern DSC capable of recognizing single fibers of microgram size, it is shown that the multiple peaks are in part or completely due to sample packing. Loosely packed fibers fill the entire volume of the pan with rather large thermal resistance to heat flow. On melting, the fibers contract and flow to collect ultimately at the bottom of the pan. This process seems to be able to cause an artifact of multistage melting dependent on the properties of the fibers. A method is proposed to greatly reduce, or even eliminate, errors of this type. The crucial elements of the analysis of melting behavior and melting temperature are decreasing the sample size and packing the individual fibers in a proper geometry, or to introduce inert media to enhance heat transport.
Date: December 31, 1996
Creator: Boller, A. & Wunderlich, B.
Partner: UNT Libraries Government Documents Department

Phase Behavior of Blends of Linear and Branched Polyethylenes on Micron-Length Scales via Ultra-Small-Angle Neutron Scattering (USANS)

Description: SANS experiments on blends of linear, high density (HD) and long chain branched, low density (LD) polyethylenes indicate that these systems form a one-phase mixture in the melt. However, the maximum spatial resolution of pinhole cameras is approximately equal to 10<sup>3</sup>Å and it has therefore been suggested that data might also be interpreted as arising from a bi-phasic melt with large a particle size (~ 1 µm), because most of the scattering from the different phases would not be resolved. We have addressed this hypothesis by means of USANS experiments, which confirm that HDPEILDPE blends are homogenous in the melt on length scales up to 20 µm. We have also studied blends of HDPE and short-chain branched linear low density polyethylenes (LLDPEs), which phase separate when the branch content is sufficiently high. LLDPEs prepared with Ziegler-Natta catalysts exhibit a wide distribution of compositions, and may therefore be thought of as a �blend� of different species. When the composition distribution is broad enough, a fraction of highly branched chains may phase separate on µm-length scales, and USANS has also been used to quantify this phenomenon.
Date: May 17, 1999
Creator: Agamalian, M.M.; Alamo, R.G.; Londono, J.D.; Mandelkern, L. & Wignall, G.D.
Partner: UNT Libraries Government Documents Department

Plasma energy recycle and conversion of polymeric (MSW) waste. Final report

Description: Final report summarizing research project results of studies of the thermal plasma recycling of polymers, including polyethylene and polypropylene. High levels of recovery of monomers were obtained from the process developed under this study.
Date: December 5, 2000
Creator: Knight, Richard & Grossman, Elihu D.
Partner: UNT Libraries Government Documents Department

Study of low-lying resonant states in 16F using an 15O radioactiveion beam

Description: A 120 MeV {sup 15}O radioactive ion beam with an intensity on target of 4.5 x 10{sup 4} pps has been developed at the 88-inch cyclotron at the Lawrence Berkeley National Laboratory. This beam has been used to study the level structure of {sup 16}F at low energies via the p({sup 15}O,p) reaction using the thick target inverse kinematics method on a polyethylene target. The experimental excitation function was analyzed using R-matrix calculations. Significantly improved values for the level widths of the four low-lying states in 16F are reported. Good agreement with the theoretical spectroscopic factors is also obtained.
Date: January 22, 2007
Creator: Lee, D.W.; Perajarvi, K.; Powell, J.; O'Neil, J.P.; Moltz, D.M.; Goldberg, V.Z. et al.
Partner: UNT Libraries Government Documents Department


Description: Samples of ultrahigh molecular weight polyethylene (UHMW-PE), polytetrafluoroethylene (PTFE), and the polyimide Vespel{reg_sign} were exposed to tritium gas in closed containers initially at 101 kPa (1 atmosphere) pressure and ambient temperature for various times up to 2.3 years. Tritium exposure effects on the samples were characterized by dynamic mechanical analysis (DMA) and radiolysis products were characterized by measuring the total final pressure and composition in the exposure containers at the end of exposure period.
Date: November 1, 2006
Creator: Clark, E & Kirk Shanahan, K
Partner: UNT Libraries Government Documents Department

Gradual change of conformational disorder

Description: The basic step of crystallization of linear macromolecules is conformational ordering. If the ordering is completed during crystallization, the entropy of fusion is a measure of the gain of conformational disorder on melting. In this lecture the possibility is discussed that in some cases conformational order changes below the glass or disordering transitions (T{sub g} and T{sub d}, respectively). Changes in conformational order below T{sub g} were observed for some flexible macromolecules without side-chains, like polyethylene. Changes below T{sub d} are found among main-chain liquid-crystalline polymers, conformationally disordered (condis) crystals, and related small-molecule model-compounds.
Date: December 31, 1994
Creator: Wunderlich, B
Partner: UNT Libraries Government Documents Department

Melting by temperature-modulated calorimetry

Description: Well-crystallized macromolecules melt irreversibly due to the need of molecular nucleation, while small molecules melt reversibly as long as crystal nuclei are present to assist crystallization. Furthermore, imperfect crystals of low-molar-mass polymers may have a sufficiently small region of metastability between crystallization and melting to show a reversing heat-flow component due to melting of poor crystals followed by crystallization of imperfect crystals which have insufficient time to perfect before the modulation switches to heating and melts the imperfect crystals. Many metals, in turn. melt sharply and reversibly as long as nuclei remain after melting for subsequent crystallization during the cooling cycle. Their analysis is complicated, however, due to thermal conductivity limitations of the calorimeters. Polymers of sufficiently high molar mass, finally, show a small amount of reversible. local melting that may be linked to partial melting of individual molecules. Experiments by temperature-modulated calorimetry and model calculations are presented. The samples measured included poly(ethylene terephthalate)s, poly(ethylene oxide)s, and indium. Two unsolved problems that arose from this research involve the origin of a high, seemingly stable, reversible heat capacity of polymers in the melting region, and a smoothing of melting and crystallization into a close-to-elliptical Lissajous figure in a heat-flow versus sample-temperature plot.
Date: September 1, 1997
Creator: Wunderlich, B.; Okazaki, Iwao; Ishikiriyama, Kazuhiko & Boller, A.
Partner: UNT Libraries Government Documents Department


Description: The mechanical impedance to blood flow in the hind limb of the dog was studied, and a dynamic relationship among the various factors affecting blood flow was derived. The blood flow through the femoral artery was routed through external polyethylene tubing containing an electromagnetic flowmeter and a Statham pressure transducer. The pulsatile blood pressure and the blood flow were displayed simultaneously on a dual-beam oscilloscope and recorded on 35-mm film. The pressure and the flow curves were then analyzed for their respective Fourier component frequencies. The Fourier analysis was performed with a frequency converter and a wave analyzer. The mechanical impedance is calculated by dividing the amplitude of each pressure harmonic by the amplitude of the corresponding flow harmonic. The average mechanical impedance vs. frequency curve has two resonant frequencies: one between 3.6 and 4.6 cps and the other between 5.6 and 7.0 cps. The impedance has a minimum value of about 1.2 peripheral resistance units at each resonant frequency. The flow vs. frequency and the pressure vs. frequency curves are also described. A theoretical electrical analog is hypothesized. This circuit consists of two arms in parallel, each arm containing an inductance and a resistance in series with a parallel capacitance and resistance. The impedence equations for the analog circuit are derived, and the impedancefrequency curve of the circuit is qualitatively constructed. This constructed curve agrees with experimental observation. The dynamic relationships existing among the elastance, inertial, and frictional factors affecting blood flow are discussed. (auth)
Date: July 1, 1960
Creator: Yanof, H M & Stacy, R W
Partner: UNT Libraries Government Documents Department

Shielding materials for high-energy neutrons

Description: The authors used the Monte Carlo transport code Los Alamos High-Energy Transport (LAHET) to study the shielding effectiveness of common shielding materials for high-energy neutrons. The source neutron spectrum was from the interaction of an 800-MeV proton beam and iron target. In a normal incident, the neutrons collided with walls made of six common shielding materials: water, concrete, iron, lead, polyethylene, and soil. The walls were of four different thicknesses: 25, 50, 75 and 100 cm. They then tallied the neutron spectra on the other side of the shielding wall and calculated the neutron doses. For the high-Z materials--iron and lead--they find that many neutrons with energies between 1--10 MeV are created when high-energy neutrons interact with shielding materials. For materials containing low-Z elements--water, soil, concrete, and polyethylene--the spectra show higher energy peaks at about 100 MeV. The studies show that for a given wall thickness, concrete is more effective than the other materials. They also studied the effectiveness of combinations of materials, such as concrete and water, concrete and soil, iron and polyethylene, or iron polyethylene and concrete.
Date: May 1, 1997
Creator: Hsu, H.H.
Partner: UNT Libraries Government Documents Department

A Simple, Inexpensive in Situ Method for Assessing Acute Toxicity of Effluents to Fish

Description: Test chambers for conducting in situ fish bioassays were constructed from 8L polyethylene bottles. Yearling fathead minnows (Pimephales promelas) and young-of-the-year bluegill (Lepomis macrochirus) demonstrated greater than 50 percent survival in the chambers after 65 days of exposure in a reservoir, river, and creek. Fathead minnow survival was substantially greater than that of bluegills. The chambers provide a simple, inexpensive, sensitive technique to screen effluents for toxicity.
Date: May 29, 2001
Creator: Wilde, E.W.
Partner: UNT Libraries Government Documents Department

Evaluation of cracking in the 241-AZ tank farm ventilation line at the Hanford Site

Description: In the period from April to October of 1988, a series of welding operations on the outside of the AZ Tank Farm ventilation line piping at the Hanford Site produced unexpected and repeated cracking of the austenitic stainless steel base metal and of a seam weld in the pipe. The ventilation line is fabricated from type 304L stainless steel pipe of 24 inch diameter and 0.25 inch wall thickness. The pipe was wrapped in polyethylene bubble wrap and buried approximately 12 feet below grade. Except for the time period between 1980 and 1987, impressed current cathodic protection has been applied to the pipe since its installation in 1974. The paper describes the history of the cracking of the pipe, the probable cracking mechanisms, and the recommended future action for repair/replacement of the pipe.
Date: October 20, 1999
Partner: UNT Libraries Government Documents Department


Description: Western Research Institute (WRI) is commercializing Diesel Dog Portable Soil Test Kits for performing analysis of fuel-contaminated soils in the field. The technology consists of a method developed by WRI (U.S. Patents 5,561,065 and 5,976,883) and hardware developed by WRI that allows the method to be performed in the field (patent pending). The method is very simple and does not require the use of highly toxic reagents. The aromatic components in a soil extract are measured by absorption at 254 nm with a field-portable photometer. WRI added significant value to the technology by taking the method through the American Society for Testing and Materials (ASTM) approval and validation processes. The method is designated ASTM Method D-5831-96, Standard Test Method for Screening Fuels in Soils. This ASTM designation allows the method to be used for federal compliance activities. In FY 99, twenty-five preproduction kits were successfully constructed in cooperation with CF Electronics, Inc., of Laramie, Wyoming. The kit components work well and the kits are fully operational. In the calendar year 2000, kits were provided to the following entities who agreed to participate as FY 99 and FY 00 JSR (Jointly Sponsored Research) cosponsors and use the kits as opportunities arose for field site work: Wyoming Department of Environmental Quality (DEQ) (3 units), F.E. Warren Air Force Base, Gradient Corporation, The Johnson Company (2 units), IT Corporation (2 units), TRC Environmental Corporation, Stone Environmental, ENSR, Action Environmental, Laco Associates, Barenco, Brown and Caldwell, Dames and Moore Lebron LLP, Phillips Petroleum, GeoSyntek, and the State of New Mexico. By early 2001, ten kits had been returned to WRI following the six-month evaluation period. On return, the components of all ten kits were fully functional. The kits were upgraded with circuit modifications, new polyethylene foam inserts, and updated instruction manuals.
Date: May 31, 2001
Partner: UNT Libraries Government Documents Department

Dynamical Properties of Polymers: Computational Modeling

Description: The free volume distribution has been a qualitatively useful concept by which dynamical properties of polymers, such as the penetrant diffusion constant, viscosity, and glass transition temperature, could be correlated with static properties. In an effort to put this on a more quantitative footing, we define the free volume distribution as the probability of finding a spherical cavity of radius R in a polymer liquid. This is identical to the insertion probability in scaled particle theory, and is related to the chemical potential of hard spheres of radius R in a polymer in the Henry's law limit. We used the Polymer Reference Interaction Site Model (PRISM) theory to compute the free volume distribution of semiflexible polymer melts as a function of chain stiffness. Good agreement was found with the corresponding free volume distributions obtained from MD simulations. Surprisingly, the free volume distribution was insensitive to the chain stiffness, even though the single chain structure and the intermolecular pair correlation functions showed a strong dependence on chain stiffness. We also calculated the free volume distributions of polyisobutylene (PIB) and polyethylene (PE) at 298K and at elevated temperatures from PRISM theory. We found that PIB has more of its free volume distributed in smaller size cavities than for PE at the same temperature.
Date: January 1, 2001
Partner: UNT Libraries Government Documents Department

LLCE burial container high density polyethylene chemical compatibility

Description: An independent chemical compatibility review of LLCE HDPE polyethylene burial containers was conducted to evaluate the container resistance to the chemicals and constituents thought to reside within the Tank Farms. The study concluded that the LLCE Burial Container fabricated from HDPE Polyethylene was a good choice for this application. The reviewer was unaware that the specification for these containers require 2 - 3 percent finely dispensed carbon black which allows long term storage outside.
Date: August 20, 1996
Creator: Veith, E.M., Westinghouse Hanford
Partner: UNT Libraries Government Documents Department

Polyethylene macroencapsulation - mixed waste focus area. OST reference No. 30

Description: The lead waste inventory throughout the US Department of Energy (DOE) complex has been estimated between 17 million and 24 million kilograms. Decontamination of at least a portion of the lead is viable but at a substantial cost. Because of various problems with decontamination and its limited applicability and the lack of a treatment and disposal method, the current practice is indefinite storage, which is costly and often unacceptable to regulators. Macroencapsulation is an approved immobilization technology used to treat radioactively contaminated lead solids and mixed waste debris. (Mixed waste is waste materials containing both radioactive and hazardous components). DOE has funded development of a polyethylene extrusion macroencapsulation process at Brookhaven National Laboratory (BNL) that produces a durable, leach-resistant waste form. This innovative macroencapsulation technology uses commercially available single-crew extruders to melt, convey, and extrude molten polyethylene into a waste container in which mixed waste lead and debris are suspended or supported. After cooling to room temperature, the polyethylene forms a low-permeability barrier between the waste and the leaching media.
Date: February 1, 1998
Partner: UNT Libraries Government Documents Department

Innovative Composites Through Reinforcement Morphology Design - a Bone-Shaped-Short-Fiber Composite

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The objective of this project is to improve the strength and toughness of conventional short-fiber composites by using innovative bone-shaped-short (BSS) fibers as reinforcement. We fabricated a model polyethylene BSS fiber-reinforced polyester-matrix composite to prove that fiber morphology, instead of interfacial strength, solves the problem. Experimental tensile and fracture toughness test results show that BSS fibers can bridge matrix cracks more effectively, and consume many times more energy when pulled out, than conventional-straight-short (CSS) fibers. This leads to both higher strength and fracture toughness for the BSS-fiber composites. A computational model was developed to simulate crack propagation in both BSS- and CSS-fiber composites, accounting for stress concentrations, interface debonding, and fiber pullout. Model predictions were validated by experimental results and will be useful in optimizing BSS-fiber morphology and other material system parameters.
Date: June 29, 1999
Creator: Zhu, Y.T.; Valdez, J.A.; Beyerlain, I.J.; Stout, M.G.; Zhou, S.; Shi, N. et al.
Partner: UNT Libraries Government Documents Department

Thermal Fusing Model of Conducting Particle Composites

Description: Composites of carbon black particles in polyethylene are known to exhibit an unusually rapid increase in resistivity as the applied field is increased, making this material useful in automatically resettable fuses. In this application the composite is in series with the circuit it is protecting: at low applied voltages this circuit is the load, but at high applied voltages the composite becomes the load, limiting the current to the circuit. We present a simple model of this behavior in terms of a network of nonlinear conductors. Each conductor has a conductance that depends on its instantaneous Joule heating. It is shown that in the fusing regime, where the current through the composite decreases with increasing voltage, an plate-like dissipation instability develops normal to the applied field. Experimental evidence of this phenomena is described.
Date: June 24, 1999
Creator: Martin, James E.
Partner: UNT Libraries Government Documents Department