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Characterization of DC-S-2000 silicone rubber as an O-ring material for laser amplifier systems

Description: We evaluated mechanical, thermal, thermodynamic, and chemical properties of Dow Corning DC-S-2000, a silicone rubber filled with silica, that was selected as an O-ring material for SHIVA laser amplifiers. We compared the properties of a batch cured in-house with the manufacturer's specifications, and we developed specific quality-control tests to evaluate future production batches of this elastomer. We also examined mechanical and thermal transitions not described in the manufacturer's bulletin. Because the silicone O-rings must function under prolonged compression, we recommend an examination of the compression properties of DC-S-2000.
Date: March 23, 1979
Creator: Hoffman, D.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Dynamic mechanical and molecular weight measurements on polymer bonded explosives from thermally accelerated aging tests. III. Kraton block copolymer binder and plasticizers

Description: The dynamic mechanical properties and molecular weight distribution of two experimental polymer bonded explosives, X-0287 and X-0298, maintained at 23, 60, and 74/sup 0/C for 3 years were examined. X-0287 is 97% 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane explosive, 1.8% Kraton G-1650, and 1.2% B/sup 2/ was 170. X-0298 is 97.4% explosive, 1.4% Kraton G-1650, and 1.2% Cenco Hi-vac oil. The relaxation associated with the Kraton rubber block glass transition is observed in both X-0287 and X-0298. In the unaged X-0298 it occurs at -59/sup 0/C and in the aged explosive at 50/sup 0/C. This is caused by migration of the oil plasticizer out of the explosive. In X-0287 the Kraton rubber block T/sub g/ is weak and broad due to the presence of the wax plasticizer. X-0287 has a second broad relaxation associated with the melting of the wax from 10 to 65/sup 0/C. The molecular weight of the Kraton binder decreased with increasing accelerated aging temperature. The oil plasticizer had no stabilizing effect, but below its melting point the wax reduced Kraton chain scission considerably. The simple random chain scission model predicted a 20.5 year use-life for X-0298, but X-0287 was stabilized against degradation below the wax melting point.
Date: January 1, 1981
Creator: Caley, L.E. & Hoffman, D.M.
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Partner: UNT Libraries Government Documents Department

Dynamic mechanical and molecular weight measurements on polymer bonded explosives from thermally accelerated aging tests. I. Fluoropolymer binders

Description: The dynamic mechanical properties and molecular weight distribution of two polymer bonded explosives, LX-10-1 and PBX-9502, maintained at 23, 60, and 74/sup 0/C for 3 years were studied. LX-10-1 is 94.5% 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane explosive bonded together with 5.5% Viton A fluoropolymer. PBX-9502 is 95% triaminotrinitrobenzene explosive bonded with 5% Kel-F-800 fluoropolymer. There are two mechanical relaxations in the LX-10-1 in the military temperature range. The relaxation at -10/sup 0/C is associated with the glass transition temperature of the Viton A binder. A second weak relaxation occurs at about 30/sup 0/C in all LX-10-1 samples tested. This relaxation is probably associated with small amounts of crystallinity in the binder although this has not been demonstrated. There is a slight increase in modulus of the LX-10-1 with accelerated aging temperature. Changes in the dynamic mechanical properties of PBX-9502 are ascribed to crystallization of the chlorotrifluoroethylene component of the Kel-F-800 binder. The molecular weight of the Viton A binder decreased slight with increasing aging temperature. Using the kinetics of random scission the activation energy for polymer degradation in the presence of the explosive was 1.19 kcal/mole. The Arrhenius preexponential term and activation energy predict an expected use-life in excess of 60 years for LX-10-1. The Kel-F-800 in PBX-9502 is also extremely stable.
Date: January 1, 1981
Creator: Hoffman, D.M. & Caley, L.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Dynamic mechanical and molecular weight measurements on polymer bonded explosives from thermally accelerated aging tests. II. A poly(ester-urethane) binder

Description: The molecular weight distribution and dynamic mechanical properties of an experimental polymer-bonded explosive, X-0282, maintained at 23, 60, and 74/sup 0/C for 3.75 y were examined, X-0282 is 95.5% 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclo-octane explosive and 4.5% Estane 5703, a segmented poly(ester-urethane). Two mechanical relaxations at about -24 and 42/sup 0/C were found in the X-0282 aged at room temperature for 3.75 years. A third relaxation at about 85/sup 0/C was found in X-0282 aged at 60 and 74/sup 0/C. The relaxation at -24/sup 0/C is associated with the soft segment glass transition of the binder. The relaxation at 42/sup 0/C is associated with the soft segment melting and may also contain a component due to the hard segment glass transition. The relaxation at 85/sup 0/C is probably associated with improved soft segment crystallite perfection. The molecular weight of the poly(ester-urethane) binder decreased significantly with increasing accelerated aging temperature. A simple random chain scission model of the urethane degradation kinetics in the presence of explosive yields an activation energy of 11.6 kcal/mole. This model predicts a use life of about 17.5 years under the worst military operating conditions (continuous operation at 74/sup 0/C).
Date: January 1, 1981
Creator: Hoffman, D.M. & Caley, L.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Characterization and Qualification of New TATB and Kel-F 800 for LX-17

Description: The project would (1) compare new FK-800 with old Kel-F 800 and KF-800 lots currently available at LLNL, (2) compare and characterize new TATB with old TATB, (3) formulate new FK-800 with wet-aminated TATB and new TATBs in according to HAAP slurry coating procedure into LX-17-2, and (4) evaluate the mechanical and detonation performance characteristics of this insensitive high explosive (IHE). Priorities will be to prove that these new materials can be formulated, pressed to density and machined; and that they contain no impurities which might cause compatibility issues. Since 3M [1, 2], LANL [7], Pantex [8] and AWE [9, 10] are currently evaluating the new FK-800, we plan to share data rather than repeating their work. Our effort is briefly described: Task 1--Evaluation of newer characterization methods to identify structural variations between old and new Kel-F 800 including: Rheological and mechanical properties, copolymer content, degree of crystallinity, and interfacial interactions with TATB. Task 2--Evaluate TATBs using scattering techniques to replace sieving operations called out in the specification [12] for particle size distribution measurements. Use SEM and OM for morphological differences between the old and new explosives. Evaluate the compaction characteristics of new TATB. Task 3--Formulation of new LX-17-2 (with new FK-800 and/or new TATB) Task 4--Evaluate mechanical and performance properties of LX-17-2. At a minimum, compressive strength, dynamic mechanical behavior and a 2-inch cylinder shot should be performed and compared with existing data for LX-17-1.
Date: February 16, 2007
Creator: Hoffman, D M & DePiero, S C
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Development of Defoamers for Confinenment Foam

Description: Aqueous foam concentrate (AFC) 380 foam was developed by Sandia National Laboratory as a blast mitigation foam for unexploded ordnance (UXO) and its ''engineered foam structure'' is reported to be able to ''envelop chemical or biological aerosols'' [1]. It is similar to commercial fire-fighting foams, consisting mostly of water with small amounts of two alcohols, an ether and surfactant. It also contains xanthan gum, probably, to strengthen the foam film and delay drainage. The concentrate is normally diluted in a 6:94 ratio with water for foaming applications. The diluted solution is normally foamed with air to an expansion factor of about 100 (density 0.01 g/cc), which is called ''dry'' foam. Higher density foam (0.18 > {rho} > 0.03 g/cc) was discovered which had quite different characteristics from ''dry'' foam and was called ''wet'' foam. Some characterization of these foams has also been carried out, but the major effort described in this document is the evaluation, at the small and medium scale, of chemical, mechanical and thermal approaches to defoaming AFC 380 foam. Several chemical approaches to defoaming were evaluated including oxidation and precipitation of the xanthan, use of commercial oil-emulsion or suspension defoamers, pH modification, and cation exchange with the surfactant. Of these the commercial defoamers were most effective. Two mechanical approaches to defoaming were evaluated: pressure and foam rupture with very fine particles. Pressure and vacuum techniques were considered too difficult for field applications but high surface area silica particles worked very well on dry foam. Finally simple thermal techniques were evaluated. An order-disorder transition occurs in xanthan solutions at about 60 C, which may be responsible for the effectiveness of hot air as a defoamer. During defoaming of 55 gallons of foam with hot air, after about 70% of the AFC 380 foam had been defoamed, the effectiveness ...
Date: August 10, 2005
Creator: Hoffman, D M & Mitchell, A R
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Density Distributions in TATB Prepared by Various Methods

Description: The density distribution of two legacy types of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) particles were compared with TATB synthesized by new routes and recrystallized in several different solvents using a density gradient technique. Legacy wet (WA) and dry aminated (DA) TATB crystalline aggregates gave average densities of 1.9157 and 1.9163 g/cc, respectively. Since the theoretical maximum density (TMD) for a perfect crystal is 1.937 g/cc, legacy TATB crystals averaged 99% of TMD or about 1% voids. TATB synthesized from phloroglucinol (P) had comparable particle size to legacy TATBs, but significantly lower density, 1.8340 g/cc. TATB synthesized from 3,5 dibromoanisole (BA) was very difficult to measure because it contained extremely fine particles, but had an average density of 1.8043 g/cc over a very broad range. Density distributions of TATB recrystallized from dimethylsulfoxide (DMSO), sulfolane, and an 80/20 mixture of DMSO with the ionic liquid 1-ethyl-3-methyl- imidazolium acetate (EMImOAc), with some exceptions, gave average densities comparable or better than the legacy TATBs.
Date: May 13, 2008
Creator: Hoffman, D M & Fontes, A T
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Fatigue of LX-14 and LX-19 plastic bonded explosives

Description: The DOD uses the plastic bonded explosive (PBX) LX-14 in a wide variety of applications including shaped charges and explosively forged projectiles. LX- 19 is a higher energy explosive, which could be easily substituted for LX-14 because it contains the identical Estane 5703p binder and more energetic CL-20 explosive. Delivery systems for large shaped charges, such as TOW-2, include the Apache helicopter. Loads associated with vibrations and expansion from thermal excursions in field operations may, even at low levels over long time periods, cause flaws, already present in the PBX to grow. Flaws near the explosive/liner interface of a shaped charge can reduce performance. Small flaws in explosives are one mechanism (the hot spot mechanism) proposed for initiation and growth to detonation of PBXs like LX-14, PBXN 5, LX-04 and LX-17 among others. Unlike cast-cured explosives and propellants, PBXs cannot usually be compression molded to full density. Generally, the amount of explosive ignited by a shock wave is approximately equal to the original void volume. Whether or not these flaws or cracks grow during field operations to an extent sufficient to adversely affect the shaped charge performance or increase the vulnerability of the PBX is the ultimate question this effort could address. Currently the fatigue life of LX-14 under controlled conditions is being studied in order to generate its failure stress as a function of the number of fatigue cycles (S- N curve). Proposed future work will address flaw and crack growth and their relationship to hot-spot concentration and explosive vulnerability to shock and/or fragment initiation.
Date: April 23, 1998
Creator: Hoffman, D. M., LLNL
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department

Small-scale cookoff bomb (SSCB) tests on solutions of DMSO/LX-10-1 and DMSO/PBX-9404

Description: The small-scale cookoff bomb test was developed by the Navy at China Lake as a method for evaluation of the violence of thermal decomposition of explosives and propellants. The UN {open_quotes}Recommendations on the Transport of Dangerous Goods - Tests and Criteria{close_quotes} (ST/SG/AC.10/11) have accepted the small-scale cookoff bomb test as a test for classification of a substance as an explosive (class 1 substance) for storage and shipment. The US Departments of Transportation and Defense have agreed to use the UN tests as US criteria for storage and shipment. The UN scheme is designed to assess the relative hazard of explosives so that an appropriate classification for transport can be made by the competent authority (DOT). Three thermal tests have been approved: the Koenen test, the internal ignition test and the small-scale cookoff bomb (SSCB) test. Lawrence Livermore National Laboratory has designed a dissolution work station for removal of the plastic bonded explosives (PBXs) LX-10-1 and PBX-9404 from two artillery fired atomic projectiles (AFAPs) using dimethyl sulfoxide (DMSO) as the solvent. The DOE Explosives Safety Manual allows up to 33% solutions of explosives to be handled as non-explosive in the laboratory and 25% solutions to be stored as non-explosives unless the explosive precipitates out. In order to ship solutions of LX-10-1 or PBX-9404 in DMSO on US highways for waste or recycling as non-explosives, these solutions must be approved for shipping by the DOT based on the results of UN test series 1. The compositions of LX-10-1 and PBX-9404 are given in Table 1. The shock sensitivity of solutions of these two plastic bonded explosives in dimethyl sulfoxide (DMSO) has been evaluated using the UN series 1 gap test for liquids as described in a previous report. The purpose of this paper is to present the results of the SSCB tests ...
Date: September 28, 1994
Creator: Helm, F. & Hoffman, D.M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department

Comparison of New and Legacy TATBs

Description: Two newly synthesized versions of the insensitive high explosive (IHE) 1,3,5-triamino-2,4,6-trinitrobenzenes (TATBs) were compared to two legacy explosives currently used by the Department of Energy. Except for thermal analysis, small scale safety tests could not distinguish between the different synthetic routes. Morphologies of new TATBs were less faceted and more spherical. The particle size distribution of one new material was similar to legacy TATBs, but the other was very fine. Densities and submicron structure of the new TATBs were also significantly different from the legacy explosives. Pressed pellets of the new explosives were less dense. Recrystallization from sulfolane improved the density and thermal stability of both new TATBs, though the morphology of the recrystallized TATB was nearly hexagonal platelets.
Date: November 8, 2007
Creator: Hoffman, D M; Willey, T M; Mitchell, A R & DePiero, S C
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Partner: UNT Libraries Government Documents Department

Formulation and Mechanical Properties of LLM-105 PBXs

Description: Eight different polymer binders were formulated with bimodal distributions of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) in 5/95 weight ratio of polymer to explosive at the 25 gram level. The polymers evaluated included: Kel-F 800, Viton A, Oxy 461, Cytop A, Hyflon AD 60, Hytemp 5545, Technoflon PFR 91 and Technoflon P 459. LLM-105 had an average particle size of 35.6 {+-} 0.6 {micro}m. This material was ground in a ball mill for 24 h to achieve a particle size of 0.72 {+-} 0.02 {micro}m. Small angle light scattering measurements were used to obtain particle size distributions on both ground and unground LLM-105. Optical microscopy was used to characterize the morphology of the crystals. Bimodal mixes of approximately 75/25% coarse to fine LLM-105 were used in all formulations. Cylinders 1.27 cm diameter by 2.54 cm long were compression molded using 3 three-minute cycles at 105 C, except in the case of Cytop and Hyflon formulations which were molded at {approx}130 C. Densities varied between 94-98% of theoretical maximum. Stress strain measurements were made in compression at -30, ambient and 74 C at a strain rate of 0.0001 sec{sup -1}. As expected, the mechanical strength scaled with temperature depending on the glass transition temperature of the polymer.
Date: April 3, 2008
Creator: Hoffman, D M; Lorenz, K T; Cunningham, B & Gagliardi, F
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Partner: UNT Libraries Government Documents Department

RX-08-HD, a low-viscosity, injection-moldable explosive for filling tortuous paths

Description: Cast cure, extrusion cast, and paste extrudable explosives have not been designed for transferring through long tortuous paths or into fine three dimensional shapes. To allow the crystalline explosive to flow a lubricating fluid is required. The energetic liquid ethane trinitrate (TMETN) was used as the lubricant to maximize the explosive energy. TMETN is a liquid nitrate ester which requires stabilization with conventional free radical stabilizers such as 2- nitrodiphenylamine, methyl-nitroanaline, or ethyl centrylite. Since these injection moldable explosives are expected to cure in place, a polyesterurethane binder based on polymeric isocyanate of hexamethylene diisocyanate and polycaprolactone polyols is dissolved in TMETN. The solubility of the polymer precursors in TMETN also reduces the energetic liquids sensitivity. The latent cure catalyst Dabco T-131 was used to minimize shrinkage associated with thermal expansion, reduce cost associated with oven cures, to give 4-6 hour potlife and overnight cure to handling strength. The product RX-08-HD is a new, low-viscosity, injection moldable explosive that can be extruded into complex, void-free shapes. Combined with appropriate design and other aspects of weaponization, RX-08-HD has produced outstanding results.
Date: October 1, 1997
Creator: Hoffman, D.M.; Jessop, E.S. & Swansiger, R.W.
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Partner: UNT Libraries Government Documents Department

Clean, agile alternative binders, additives and plasticizers for propellant and explosive formulations

Description: As part of the Strategic Environmental Research and Development Program (SERDP) a clean, agile manufacturing of explosives, propellants and pyrotechniques (CANPEP) effort set about to identify new approaches to materials and processes for producing propellants, explosives and pyrotechniques (PEP). The RDX based explosive PBXN-109 and gun propellant M-43 were identified as candidates for which waste minimization and recycling modifications might be implemented in a short time frame. The binders, additives and plasticizers subgroup identified cast non-curable thermoplastic elastomer (TPE) formulations as possible replacement candidates for these formulations. Paste extrudable explosives were also suggested as viable alternatives to PBXN-109. Commercial inert and energetic TPEs are reviewed. Biodegradable and hydrolyzable binders are discussed. The applicability of various types of explosive formulations are reviewed and some issues associated with implementation of recyclable formulations are identified. It is clear that some processing and weaponization modifications will need to be made if any of these approaches are to be implemented. The major advantages of formulations suggested here over PBXN-109 and M-43 is their reuse/recyclability. Formulations using TPE or Paste could by recovered from a generic bomb or propellant and reused if they met specification or easily reprocessed and sold to the mining industry.
Date: December 1, 1994
Creator: Hoffman, D.M.; Hawkins, T.W. & Lindsay, G.A.
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Partner: UNT Libraries Government Documents Department

What Have We Learned From Decades of CRT, And Where Do We Go From Here?

Description: The Chemical Reactivity Test, or CRT, has been the workhorse for determining short-to-medium term compatibility and thermal stability for energetic materials since the mid 1960s. The concept behind the CRT is quite simple. 0.25 g of material is heated in a 17 cm{sup 3} vessel for 22 hours at 80, 100, or 120 C, and the yield of gaseous products are analyzed by gas chromatography to determine its thermal stability. The instrumentation is shown in Figure 1, and the vessel configuration is shown in Figure 2. For compatibility purposes, two materials, normally 0.25 g of each, are analyzed as a mixture. Recently, data from the past 4 decades have been compiled in an Excel spreadsheet and inspected for reliability and internal consistency. The resulting processed data will be added this year to the LLNL HE Reference Guide. Also recently, we have begun to assess the suitability of the CRT to answer new compatibility issues, especially in view of more modern instrumentation now available commercially. One issue that needs to be addressed is the definition of thermal stability and compatibility from the CRT. Prokosch and Garcia (and the associated MIL-STD-1751A) state that the criterion for thermal stability is a gas yield of less than 4 cm{sup 3}/g for a single material for 22 hours at 120 C. The gases from energetic materials of interest ordinarily have an average molecular weight of about 36 g/mol, so this represents decomposition of 0.5-1.0% of the sample. This is a reasonable value, and a relatively unstable energetic material such as PETN has no problem passing. PBX 9404, which yields 1.5 to 2.0 cm{sup 3}/g historically, is used as a periodic check standard. This is interesting in itself, since the nitrocellulose in the 9404 is unstable and probably has partially decomposed over the decades. However, it ...
Date: September 11, 2006
Creator: Burnham, A K; Souers, P C; Gagliardi, F J; Weese, R K; DePiero, S C; Tran, T et al.
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Partner: UNT Libraries Government Documents Department

New deposition processes for the growth of oxide and nitride thin films

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The goal of this effort is to study the use of homoleptic metal amido compounds as precursors for chemical vapor deposition (CVD). The amides offer potential for the deposition of a variety of important materials at low temperatures. The establishment of these precursor compounds will enhance the ability to exploit the properties of advanced materials in numerous coatings applications. Experiments were performed to study the reactivity of Sn[NMe{sub 2}]{sub 4} with oxygen. The data demonstrated that gas-phase insertion of oxygen into the Sn-N bond, leading to a reactive intermediate, plays an important role in tin oxide deposition. Several CVD processes for technologically important materials were developed using the amido precursor complexes. These included the plasma enhanced CVD of TiN and Zr{sub 3}N{sub 4}, and the thermal CVD of GaN and Al N. Quality films were obtained in each case, demonstrating the potential of the amido compounds as CVD precursors.
Date: November 1, 1998
Creator: Apen, E.A.; Atagi, L.M.; Barbero, R.S.; Espinoza, B.F.; Hubbard, K.M.; Salazar, K.V. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department