176 Matching Results

Search Results

Advanced search parameters have been applied.

Nanohybrids Based on Solid and Foam Polyurethanes

Description: Polymer nanocomposites are a going part of Materials Science and Engineering. These new composite materials exhibit dimensional and thermal stability of inorganic materials and toughness and dielectric properties of polymers. Development of nanocomposites become an important approach to create high-performance composite materials. In this study silica, fly ash, silica nanotubes and carbon black particles have been added to modify polyurethane foam and thermoplastic polyurethanes. It has been found that the addition of silica can diminish the size of foam bubbles, resulting in an increased stiffness of the material, increase of the compressive strength, and greater resistance to deformation. However, the uniformity of bubbles is reduced, resulting in increased friction of the material. Fly ash added to the foam can make bubbles smaller and improve uniformity of cells. Therefore, the material stiffness and compressive strength, resistance to deformation, and has little impact on the dynamic friction of the material. Adding nanotubes make bubble size unequal, and the arrangement of the bubble uneven, resulting in decreased strength of the material, while the friction increases. After the addition of carbon black to the polyurethane foam, due to the special surface structure of the carbon black, the foam generates more bubbles during the foaming process changing the foam structure. Therefore, the material becomes soft, we obtain a flexible polyurethane foam. The results of mechanical properties determination of the thermoplastic polyurethane that adding particles may increase the stiffness and wear resistance of the thermoplastic polyurethane, while the tensile properties of the material are reduced. This phenomenon may be due to agglomeration of particles during the mixing process. Possibly the particles cannot be uniformly dispersed in the thermoplastic polyurethane.
Date: May 2015
Creator: Bo, Chong
Partner: UNT Libraries

Zirconium Pheylarsonate Tracer Scale Method for the Differentiation of Pu(III) and Pu(IV) in Redox Solutions

Description: The following report studies an estimation of the amount of Pu(III) and Pu(IV) present in the IBP Stream, with the purpose of establishing an analytical, method suitable for routine control analysis. A method is discussed that is based on carrying Pu(IV) upon a zirconium phanylarsonate precipitate.
Date: June 30, 1948
Creator: Ice, C. H.
Partner: UNT Libraries Government Documents Department

SPUF - a simple polyurethane foam mass loss and response model.

Description: A Simple PolyUrethane Foam (SPUF) mass loss and response model has been developed to predict the behavior of unconfined, rigid, closed-cell, polyurethane foam-filled systems exposed to fire-like heat fluxes. The model, developed for the B61 and W80-0/1 fireset foam, is based on a simple two-step mass loss mechanism using distributed reaction rates. The initial reaction step assumes that the foam degrades into a primary gas and a reactive solid. The reactive solid subsequently degrades into a secondary gas. The SPUF decomposition model was implemented into the finite element (FE) heat conduction codes COYOTE [1] and CALORE [2], which support chemical kinetics and dynamic enclosure radiation using 'element death.' A discretization bias correction model was parameterized using elements with characteristic lengths ranging from 1-mm to 1-cm. Bias corrected solutions using the SPUF response model with large elements gave essentially the same results as grid independent solutions using 100-{micro}m elements. The SPUF discretization bias correction model can be used with 2D regular quadrilateral elements, 2D paved quadrilateral elements, 2D triangular elements, 3D regular hexahedral elements, 3D paved hexahedral elements, and 3D tetrahedron elements. Various effects to efficiently recalculate view factors were studied -- the element aspect ratio, the element death criterion, and a 'zombie' criterion. Most of the solutions using irregular, large elements were in agreement with the 100-{micro}m grid-independent solutions. The discretization bias correction model did not perform as well when the element aspect ratio exceeded 5:1 and the heated surface was on the shorter side of the element. For validation, SPUF predictions using various sizes and types of elements were compared to component-scale experiments of foam cylinders that were heated with lamps. The SPUF predictions of the decomposition front locations were compared to the front locations determined from real-time X-rays. SPUF predictions of the 19 radiant heat experiments were also ...
Date: July 1, 2003
Creator: Hobbs, Michael L. & Lemmon, Gordon H.
Partner: UNT Libraries Government Documents Department

Epoxy Foam Encapsulants: Processing and Dielectric Characterization

Description: The dielectric performance of epoxy foams was investigated to determine if such materials might provide advantages over more standard polyurethane foams in the encapsulation of electronic assemblies. Comparisons of the dielectric characteristics of epoxy and urethane encapsulant foams found no significant differences between the two resin types and no significant difference between as-molded and machined foams. This study specifically evaluated the formulation and processing of epoxy foams using simple methylhydrosiloxanes as the flowing agent and compared the dielectric performance of those to urethane foams of similar density.
Date: January 1, 1999
Creator: Domeier, Linda & Hunter, Marion
Partner: UNT Libraries Government Documents Department

Materials Compatibility and Migration in Polymer Systems

Description: This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project to study the effects of materials migration by direct measurement of the diffusion and convective migration processes in complex polymeric materials and to develop appropriate predictive models. The use of isotopically tagged probe molecules to measure in-situ the diffusion of water in estane was demonstrated. A special environmental cell with a thin window was fabricated to enable real time measurements to be made under realistic conditions simulating actual operating parameters. Depth profiles were measured quantitatively using ion beam methods available at the Los Alamos Ion Beam Materials Laboratory. The Williams-Landau-Ferry model was adopted as a general expression for diffusion of a volatile material in a polymer. This model contains both thermal activation and free-volume change effects to account for the changes in polymeric structure with temperature and physical properties as embodied in the glass-transition temperature. A theoretical simulation of water migration in polyurethane was performed and compared to the ideal 1-D, constant temperature, constant-boundary concentration test problem, for which an analytical solution is known. The transport code works properly and indicates that time steps on the order of 10 minutes are permissible, which is the order of the time required to collect data for one measurement in the ion beam.
Date: July 10, 1999
Creator: Maggiore, C.J. & Valone, S.
Partner: UNT Libraries Government Documents Department


Description: In this investigation, a simple experimental technique, dot-matrix deposition and mapping, was developed to study the full-field deformation in a polymeric foam specimen. One of the advantages of using this technique is that it can be easily applied to situations where large deformations are involved. The spatial resolution of the current technique is not as high as the digital image correlation method and some other optical techniques. Nevertheless, because the largest cell diameter of the polyurethane foam studied in this investigation is about 1 mm, the smallest length scale over which the polymeric foam material can be treated as a homogeneous solid would be at least several millimeters. For the element size used in the present study in the range of 2.5 x 2.5 mm, the dot-matrix deposition and mapping technique would provide enough detail about the behavior of polymeric foam materials under complicated deformation states and under complicated loading conditions. It will also provide useful information to compare with numerical simulations so that the constitutive models can be validated.
Date: March 1, 2001
Creator: LIU, C. & AL, ET
Partner: UNT Libraries Government Documents Department

Weapon foam accelerated aging using dynamic mechanical analysis

Description: Rigid polyurethane foams are used for supports and as encapsulants for electronic assemblies in almost all weapon systems. Mechanical properties (storage, loss, rubbery, and glassy moduli) of three foams are being evaluated; the test scheme is illustrated. Aging tests are also being run on the long-term performance of foams being used in the Russian Fissile Material Container; there was no significant change in the glass transition temperature, glassy modulus, or rubbery modulus after one year of aging.
Date: March 1, 1996
Creator: Rand, P.B. & Hance, B.G.
Partner: UNT Libraries Government Documents Department

Characterization of polyurethane systems which contain low levels of free TDI

Description: EN-7, EN-8, and EN-9 are polyurethane systems that are used in numerous applications in the Department of Energy complex. These systems contain high levels of toluene diisocyanate (TDI). Currently, TDI is being treated as a suspect human carcinogen within the Department of Energy complex. This report documents the results of a material characterization study of three polyurethane systems that contain low levels of free (potentially airborne) TDI. The characterization has been accomplished by performing a set of statistically designed experiments. The purpose of these experiments is to explore the effects of formulation and cure schedule on various material properties. In general, the material properties (pot life, glass transition temperature, hardness, and tear strength) were relatively insensitive to variation in the cure schedule. On the other hand, variation in curative level had measurable effects on material properties for the polyurethane systems studied. Furthermore, the material properties of the three low-free-TDI polyurethane systems were found to be comparable or superior (for certain curative levels) to commonly-used polyurethane systems. Thus, these low-free-TDI systems appear to be viable candidates for applications where a polyurethane is needed.
Date: April 1, 1995
Creator: Myers, R.L. & Thomas, E.V.
Partner: UNT Libraries Government Documents Department

Case study for model validation : assessing a model for thermal decomposition of polyurethane foam.

Description: A case study is reported to document the details of a validation process to assess the accuracy of a mathematical model to represent experiments involving thermal decomposition of polyurethane foam. The focus of the report is to work through a validation process. The process addresses the following activities. The intended application of mathematical model is discussed to better understand the pertinent parameter space. The parameter space of the validation experiments is mapped to the application parameter space. The mathematical models, computer code to solve the models and its (code) verification are presented. Experimental data from two activities are used to validate mathematical models. The first experiment assesses the chemistry model alone and the second experiment assesses the model of coupled chemistry, conduction, and enclosure radiation. The model results of both experimental activities are summarized and uncertainty of the model to represent each experimental activity is estimated. The comparison between the experiment data and model results is quantified with various metrics. After addressing these activities, an assessment of the process for the case study is given. Weaknesses in the process are discussed and lessons learned are summarized.
Date: October 1, 2004
Creator: Dowding, Kevin J.; Leslie, Ian H. (New Mexico State University, Las Cruces, NM); Hobbs, Michael L.; Rutherford, Brian Milne; Hills, Richard Guy (New Mexico State University, Las Cruces, NM) & Pilch, Martin M.
Partner: UNT Libraries Government Documents Department

CPUF - a chemical-structure-based polyurethane foam decomposition and foam response model.

Description: A Chemical-structure-based PolyUrethane Foam (CPUF) decomposition model has been developed to predict the fire-induced response of rigid, closed-cell polyurethane foam-filled systems. The model, developed for the B-61 and W-80 fireset foam, is based on a cascade of bondbreaking reactions that produce CO2. Percolation theory is used to dynamically quantify polymer fragment populations of the thermally degrading foam. The partition between condensed-phase polymer fragments and gas-phase polymer fragments (i.e. vapor-liquid split) was determined using a vapor-liquid equilibrium model. The CPUF decomposition model was implemented into the finite element (FE) heat conduction codes COYOTE and CALORE, which support chemical kinetics and enclosure radiation. Elements were removed from the computational domain when the calculated solid mass fractions within the individual finite element decrease below a set criterion. Element removal, referred to as ?element death,? creates a radiation enclosure (assumed to be non-participating) as well as a decomposition front, which separates the condensed-phase encapsulant from the gas-filled enclosure. All of the chemistry parameters as well as thermophysical properties for the CPUF model were obtained from small-scale laboratory experiments. The CPUF model was evaluated by comparing predictions to measurements. The validation experiments included several thermogravimetric experiments at pressures ranging from ambient pressure to 30 bars. Larger, component-scale experiments were also used to validate the foam response model. The effects of heat flux, bulk density, orientation, embedded components, confinement and pressure were measured and compared to model predictions. Uncertainties in the model results were evaluated using a mean value approach. The measured mass loss in the TGA experiments and the measured location of the decomposition front were within the 95% prediction limit determined using the CPUF model for all of the experiments where the decomposition gases were vented sufficiently. The CPUF model results were not as good for the partially confined radiant heat experiments where the ...
Date: July 1, 2003
Creator: Fletcher, Thomas H. (Brigham Young University, Provo, UT); Thompson, Kyle Richard; Erickson, Kenneth L.; Dowding, Kevin J.; Clayton, Daniel (Brigham Young University, Provo, UT); Chu, Tze Yao et al.
Partner: UNT Libraries Government Documents Department


Description: Polyurethane foam has been employed in impact limiters for large radioactive materials packagings since the early 1980's. Its consistent crush response, controllable structural properties and excellent thermal insulating characteristics have made it attractive as replacement for the widely used cane fiberboard for smaller, drum size packagings. Accordingly, polyurethane foam was chosen for the overpack material for the 9977 and 9978 packagings. The study reported here was undertaken to provide data to support the analyses performed as part of the development of the 9977 and 9978, and compared property values reported in the literature with published property values and test results for foam specimens taken from a prototype 9977 packaging. The study confirmed that, polyurethane foam behaves in a predictable and consistent manner and fully satisfies the functional requirements for impact absorption and thermal insulation.
Date: February 18, 2009
Creator: Smith, A; Glenn Abramczyk, G; Paul Blanton, P; Steve Bellamy, S; William Daugherty, W & Sharon Williamson, S
Partner: UNT Libraries Government Documents Department

Effects of Temperature and Humidity on Wilethane 44 Cure

Description: Wilethane 44 is a polyurethane adhesive developed by the Materials Team within ESA-MEE at Los Alamos National Laboratory as a replacement for Hexcel Corporation Urethane 7200. Urethane 7200 is used in numerous weapon systems, but it was withdrawn from the market in 1989. The weapons complex requires a replacement material for use in the W76-1 LEP and the W88, as well as for assembly of JTAs for other warheads. All polyurethane systems are susceptible to moisture reacting with unreacted isocyanate groups. This side reaction competes with the curing reaction and results in CO{sub 2} formation. Therefore, a polyurethane adhesive can exhibit foaming if appropriate environmental controls are not in place while it cures. A designed experiment has been conducted at TA-16-304 to determine the effects of ambient conditions on the properties of cured Wilethane 44. Temperature was varied from 15 C to 30 C and relative humidity from 15% to 40%. The density, hardness at 24 hours, and butt tensile strength on aluminum substrates were measured and fitted to quadratic equations over the experimental space. Additionally, the loss and storage moduli during cure were monitored as a function of cure temperature. These experiments provide a stronger basis for establishing appropriate environmental conditions and cure times when using Wilethane 44. The current guidelines are a working time of 90 minutes, a cure time of 18 hours, and a relative humidity of less than 25%, regardless of ambient temperature. Viscosity measurements revealed that the working time is a strong function of temperature and can be as long as 130 minutes at 15 C or as short as 90 minutes at 30 C. The experiments also showed that the gel time is much longer than originally thought, as long as 13 hours at 15 C. Consequently, it may be necessary to extend the ...
Date: October 1, 2006
Creator: Weigle, John C.
Partner: UNT Libraries Government Documents Department

FLASHFOAM : a triboluminescent polymer foam for mechanical sensing.

Description: The formulation and processing of a brittle polyurethane foam containing triboluminescent powder additives is described. Two powder additives, known to exhibit triboluminescence, were individually examined: triethylammonium tetrakis (dibenzoylmethanato) europate [NEt3H][Eu(DBM)4] and ordinary table sugar (sucrose, C12H22O11). In each instance, the powders were mixed into the polyol component of the foam. When combined with the isocyanate component, the resulting foams had these powders incorporated into their cellular structure so as to induce a triboluminescent response upon crushing during impact testing. The triboluminescent response of foam specimens containing each of these powder additives was characterized by measuring: the time rate of change in the optical output (measured as Watts), the peak optical output, the total integrated output (Watt-seconds), during the impact event. Foams containing the europate compound were found to yield several orders of magnitude higher output when compared to the sugar-containing foam. Strain rate and concentration of the powder (in the foam) were important variables with respect to optical output. Both the peak and total triboluminescent output increased with increasing powder concentration. Peak output was also found to increase with increasing strain rate. However, the total output was found to be roughly constant for a given concentration regardless of strain rate (over the strain rate range: 20 sec-1< e& < 150 sec-1). At very low strain rates, no triboluminescent response was measured.
Date: July 1, 2003
Creator: Dentinger, Paul M.; Whinnery, LeRoy L., Jr. & Goods, Steven Howard
Partner: UNT Libraries Government Documents Department


Description: In the thermal analysis of the 9977 package, it was found that calculated temperatures, determined using a typical thermal analysis code, did not match those measured in the experimental apparatus. The analysis indicated that the thermal resistance of the overpack in the experimental apparatus was less than that expected, based on manufacturer's reported value of thermal conductivity. To resolve this question, the thermal conductivity of the installed foam was evaluated from the experimental results, using a simplified analysis. This study confirmed that the thermal resistance of the experimental apparatus was lower than that which would result from the manufacturer's published values for thermal conductivity of the foam insulation. The test package was sectioned to obtain samples for measurement of material properties. In the course of the destructive examination a large uninsulated region was found at the bottom of the package, which accounted for the anomalous results. Subsequent measurement of thermal conductivity confirmed the manufacturer's published values. The study provides useful insight into the use of simplified, scoping calculations for evaluation of thermal performance of packages.
Date: December 5, 2007
Creator: Smith, A; Bruce Hardy, B; Kurt Eberl, K & Nick Gupta, N
Partner: UNT Libraries Government Documents Department


Description: Polyurethane foam has been widely used as an impact absorbing and thermal insulating material for large radioactive materials packages, since the 1980's. With the adoption of the regulatory crush test requirement, for smaller packages, polyurethane foam has been adopted as a replacement for cane fiberboard, because of its ability to withstand the crush test. Polyurethane foam is an engineered material whose composition is much more closely controlled than that of cane fiberboard. In addition, the properties of the foam can be controlled by controlling the density of the foam. The conditions under which the foam is formed, whether confined or unconfined have an affect on foam properties. The study reported here reviewed the application of polyurethane foam in RAM packagings and compared property values reported in the literature with published property values and test results for foam specimens taken from a prototype 9977 packaging. The study confirmed that, polyurethane foam behaves in a predictable and consistent manner and fully satisfies the functional requirements for impact absorption and thermal insulation.
Date: May 15, 2007
Creator: Smith, A; Glenn Abramczyk, G; Paul Blanton, P; Steve Bellamy, S; William Daugherty, W & Sharon Williamson, S
Partner: UNT Libraries Government Documents Department


Description: An experiment was conducted to determine the puncture resistance of 15 gloves that are used or proposed for use in the Tritium Facility at Savannah River Site (SRS). These data will serve as a baseline for characterization and may be incorporated into the glove procurement specification. The testing was conducted in agreement with ASTM D120 and all of the gloves met or exceeded the minimum requirements. Butyl gloves exhibited puncture resistance nearly 2.5 times the minimum requirements at SRS while Polyurethane was nearly 7.5x the minimum.
Date: February 29, 2012
Creator: Korinko, P. & Chapman, G.
Partner: UNT Libraries Government Documents Department

Contributions of kinematics and viscoelastic lap deformation on the suface figure during full aperture polishing of fused silica

Description: A typical optical fabrication process involves a series of basic process steps including: (1) shaping, (2) grinding, (3) polishing, and sometimes (4) sub-aperture tool finishing. With significant innovation and development over the years in both the front end (shaping using CNC machines) and the back end (sup-aperture tool polishing), these processes have become much more deterministic. However, the intermediate stages (full aperture grinding/polishing) in the process, which can be very time consuming, still have much reliance on the optician's insight to get to the desired surface figure. Such processes are not presently very deterministic (i.e. require multiple iterations to get desired figure). The ability to deterministically finish an optical surface using a full aperture grinding/polishing will aid optical glass fabricators to achieve desired figure in a more repeatable, less iterative, and more economical manner. Developing a scientific understanding of the material removal rate is a critical step in accomplishing this. In the present study, the surface figure and material removal rate of a fused silica workpiece is measured as a function of polishing time using Ceria based slurry on a polyurethane pad or pitch lap under a variety of kinematic conditions (motion of the workpiece and lap) and loading configurations. The measured results have been applied to expand the Preston model of material removal (utilizing chemical, mechanical and tribological effects). The results show that under uniform loading, the surface figure is dominated by kinematics which can be predicted by calculating the relative velocity (between the workpiece and the lap) with time and position on the workpiece. However, in the case where the kinematics predict a time-averaged removal function over the workpiece that is uniform, we find experimentally that the surface deviates significantly from uniform removal. We show that this non-uniform removal is caused by the non-uniform stress distribution resulting from ...
Date: October 9, 2007
Creator: Suratwala, T I; Steele, R A & Feit, M D
Partner: UNT Libraries Government Documents Department

Material removal and surface figure during pad polishing of fused silica

Description: The material removal and surface figure after ceria pad polishing of fused silica glass have been measured and analyzed as a function of kinematics, loading conditions, and polishing time. Also, the friction at the workpiece/lap interface, the slope of the workpiece relative to the lap plane, and lap viscoelastic properties have been measured and correlated to material removal. The results show that the relative velocity between the workpiece & lap (determined by the kinematics) and the pressure distribution determine the spatial and temporal material removal and hence the final surface figure of the workpiece. In the case where the applied loading and relative velocity distribution over the workpiece are spatially uniform, a significant non-uniform spatial material removal from the workpiece surface is observed. This is due to a non-uniform pressure distribution resulting from: (1) a moment caused by a pivot point and interface friction forces; (2) viscoelastic relaxation of the polyurethane lap; and (3) a physical workpiece/lap interface mismatch. Both the kinematics and these contributions to the pressure distribution are quantitatively described, and then combined to form a spatial and temporal Preston model & code for material removal (called Surface Figure or SurF{copyright}). The surface figure simulations are consistent with the experiment for a wide variety of polishing conditions. This study is an important step towards deterministic full-aperture polishing, which would allow optical glass fabrication to be performed in a more repeatable, less iterative, and hence more economical manner.
Date: May 4, 2009
Creator: Suratwala, T I; Feit, M D & Steele, W A
Partner: UNT Libraries Government Documents Department

A performance evaluation of coating systems for long term aqueous immersion service

Description: The static immersion of coated steel panels in various media representative of chemical and waste processes around the Oak Ridge Y-12 Plant was terminated after 16 months exposure for evaluation of coating performance and comparison with observations collected following 1, 6, and 11 months exposure. In each environment, a wide range of coating performance was observed, including some coatings unsuitable for use in the test environment (despite the high recommendation of the vendor). Further, coating performance as a function of time suggests a test duration of at least several months is required to fully assess candidate coating performance for specific applications. The performance of many coatings, particularly in the most alkaline environment, was adversely affected by the imposition of supplemental cathodic protection on the coated test panels.
Date: November 8, 1994
Creator: Pawel, S.J.
Partner: UNT Libraries Government Documents Department

A reconsideration of the measurements with the O ring stack

Description: The measurements made this year of Rn entry to the O ring stack were interpreted to be diffusion through the urethane O rings; however the alternative hypothesis is that Rn was mainly entering the stack by leakage through a small hole. This note presents a calculation of diffusion from first principles and rederives the diffusion constant for the O ring stack measurements.
Date: September 1, 1996
Creator: Cleveland, B. T. & Rowley, J.K.
Partner: UNT Libraries Government Documents Department