ABL and BAM Friction Analysis Comparison

The Integrated Data Collection Analysis (IDCA) program has conducted a proficiency study for Small‐Scale Safety and Thermal (SSST) testing of homemade explosives (HMEs). Described here is a comparison of the Alleghany Ballistic Laboratory (ABL) friction data and Bundesanstalt für Materialforschung und ‐prüfung (BAM) friction data for 19 HME and military standard explosives. Two methods were employed to reduce the data – modified Bruceton analysis (F₅₀) and the threshold initiation level analysis (TIL). The study provides a full list of friction sensitivity data for the 19 materials by both ABL and BAM friction testing equipment. Specific results highlight the differences more than the similarities of the two methods. PETN and KClO₃/sugar mixtures exhibit the most sensitivity of the materials studied by both testing methods. On the other hand, H₂O₂/fuel mixtures exhibit no sensitivity in ABL testing, but exhibit some sensitivity in BAM testing. For the UNi mixtures, the behavior was the opposite, no sensitivity in BAM but some sensitivity in ABL. KClO₄/Al mixtures exhibit high sensitivity in the ABL method, but only moderate sensitivity in the BAM method. Other differences are seen in the relative sensitivities underscoring the differences in the mechanisms of how each test method operates. In some cases, data could not be attained because of the physical nature of the material. Comparison between the two friction methods on a material‐by‐material basis using absolute values not surprisingly yielded essentially no systematic correlations. Even the relative order showed little correlation between the two methods. The Department of Homeland Security (DHS) funded this effort. Each participating testing laboratory uses identical test materials and preparation methods. However, the test procedures differ among the laboratories. The testing performers involved are Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), Naval Surface Warfare Center, Indian Head Division Explosive Ordnance Disposal Technology (NSWC IHEODTD), Sandia National Laboratories (SNL), and Air Force Research Laboratory (AFRL/RXQL).     

MODIFIED DIFFERENTIAL THERMAL ANALYSIS APPARATUS*

The differential thermal analysis apparatus described consists of an important improvement. This is the arrangement of the sample and standard holder so that the thermocouples become both the holder and the differential temperature measuring device. This arrangement permits easy removal of the sample and also permits the investigation of exothermic and endothermic reactions at much higher temperatures without damage to the thermocouples.     

Variation of Methods in Small‐Scale Safety and Thermal Testing of Improvised Explosives

One of the first steps in establishing safe handling procedures for explosives is small‐scale safety and thermal (SSST) testing. To better understand the response of homemade or improvised explosives (HMEs) to SSST testing, 16 HME materials were compared to three standard military explosives in a proficiency‐type round robin study among five laboratories, two U.S. Department of Defense and three U.S. Department of Energy, sponsored by the Department of Homeland Security, Science & Technology Directorate, Explosives Division. The testing included impact, friction, electrostatic discharge (ESD) and thermal. The testing matrix was designed to address problems encountered with improvised materials: powder mixtures, liquid suspensions, partially wetted solids, immiscible liquids, and reactive materials. All testing materials and/or precursors came from the same batch distributed to each of the participants and were handled, pretreated, and mixed by standardized procedures. For this proficiency test, the participants had similar equipment, usually differing by vintage. This allowed for a direct comparison of the results from each participant to the average of the results from all the participants. Some general trends observed for each series of tests were: (1) Drop hammer – LLNL usually found the materials less sensitive than the average with materials that have high sensitivity to impact and LANL usually found the materials less sensitive than the average with materials that have high sensitivity to impact; (2) friction – LLNL found the materials less sensitive than the average; (3) and ESD – IHD usually found the materials less sensitive than the average. In this report, the proficiency test data from all the participants is compared and contrasted for impact, selected friction, and ESD testing. Other friction and thermal data will be addressed elsewhere as well as the statistical analysis of several repeated measurements on the proficiency test standards.     

Statistical Analysis of an Inter‐Laboratory Comparison of Small‐Scale Safety and Thermal Testing of RDX

The Integrated Data Collection Analysis (IDCA) program has conducted a proficiency test for small‐scale safety and thermal (SSST) testing of homemade explosives (HMEs). Described here are statistical analyses of the results from this test for impact, friction, electrostatic discharge, and differential scanning calorimetry analysis of the RDX Class 5 Type II standard. The material was tested as a well‐characterized standard several times during the proficiency test to assess differences among participants and the range of results that may arise for well‐behaved explosive materials. The analyses show there are detectable differences among the results from IDCA participants. While these differences are statistically significant, most of them can be justified for comparison purposes to assess potential variability when laboratories attempt to measure identical samples using methods assumed to be nominally the same. The results presented in this report include the average sensitivity results from the IDCA participants and the ranges of values obtained. The ranges represent variation about the mean values of the tests of between 26 % and 42 %. The magnitude of this variation is attributed to differences in operator, method, and environment as well as the use of different instruments that are also of varying age. The results appear to be a good representation of results generated by the broader safety testing community based on the range of methods, instruments, and environments included in the IDCA proficiency test.     

Investigation on the Reaction of Powdered Tin as a Metallic Fuel with Some Pyrotechnic Oxidizers

Thermogravimetry (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC) have been used to examine the thermal behavior of Sn+KClO₃, Sn+KNO₃, and Sn+KClO₄ pyrotechnic systems and the results were compared with thermal characteristics of individual constituents. TG curves for tin powder, heated alone in air, showed a relatively slow oxidation above 570 °C. From thermal results the decomposition temperatures of KClO₃, KClO₄, and KNO₃, in nitrogen atmosphere, were measured at 472, 592 and 700 °C, respectively. For the Sn+KNO₃ pyrotechnic system, the tin oxidation was completed within the range of 480 to 500 °C. Replacing KNO₃ with KClO₄ led to an increase of thermal stability of the pyrotechnic mixture. Among above‐mentioned pyrotechnic mixtures, Sn+KClO₃ has the lowest ignition temperature at about 390 °C. The apparent activation energy (E), ΔG^#, ΔH^# and ΔS^# of the combustion processes were obtained from the DSC experiments. Based on these kinetic data and ignition temperatures, the relative reactivity of these mixtures was found to obey in the following order: Sn+KClO₃>Sn+KNO₃>Sn+KClO₄.     

Characterization and performance of melamine enhanced urea formaldehyde resin for bonding southern pine particleboard

Urea‐formaldehyde resins modified by melamine were synthesized by four catalysts (H₂SO₄, HCl, H₃PO₄, and NaOH/NH₄OH) with a F/U/M molar ratio of 1.38/1/0.074. Resin structure and thermal behavior were studied by ¹³C‐NMR and DSC techniques. For H₂SO₄, HCl, and H₃PO₄ catalysts, resins were prepared by two stage pH adjustment: the first pH stage was set at 1.25 (H₃PO₄ pH 1.60) and second pH stage was set at 5.0. For the NaOH/NH₄OH catalyst, the resin was set at pH 5.0 from the start. Of the four catalysts, HCl catalyzed resins, with the highest free urea and lowest free formaldehyde, consistently yielded the lowest formaldehyde emission; NaOH/NH₄OH catalyst resulted in the best IB strength tested at dry conditions and also after 24 h cold water soak and the lowest water absorption and thickness swell. The resins catalyzed with H₃PO₄ had the highest free formaldehyde and no free urea yielding the highest formaldehyde emission. Each DSC thermogram was proceeded by a weak exothermic peak and followed by an obvious endothermic peak. The exothermic peak temperatures were 125.0, 131.1, 111.4, and 125.2°C, and endothermic peak temperatures were 135.8, 147.6, 118.9, and 138.4°C, respectively, for H₂SO₄, HCl, H₃PO₄, and NaOH/NH₄OH catalysts. The close proximity of the peak temperatures of the exothermic and endothermic reactions strongly suggests that there is potential interference of heat flow between the exothermic and endothermic reactions which may impact resin curing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermo‐Rheology of a Proline‐Based Surface‐Active Ionic Liquid: Mixtures with Water and n‐Octane

Surfactant flooding is one of the most promising techniques to recover oil from unprofitable reservoirs. Surface‐active ionic liquids can overcome the limitations of the current surfactants. The rheology of the injecting solutions and the formed slugs is critical in the evaluation of an enhanced oil recovery process. The thermo‐rheological behavior of a biodegradable surface‐active ionic liquid, [ProC₄]DS, and the corresponding binary and ternary mixtures with water and n‐octane was studied. All flow curves exhibited shear‐thinning and thixotropic behavior. The viscoelastic behavior of the ternary samples depended strongly on the [ProC₄]DS content. Three different regions were identified: typical liquid‐like behavior, weak gel, and true gel. The thermal profiles indicated that the tested systems were fully thermoreversible.     

Unusual effect of filler (CaCO3) on thermal degradation of polyurethane

The thermal degradation of polyurethane is exothermic in nature. The addition of CaCO₃ inverts the exothermicity to endothermic behavior in the presence of air. © 1994 John Wiley & Sons, Inc.     

Recuperative coupling of exothermic and endothermic reactions

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions improves the thermal efficiency of processes and reduces the size of the reactors. One type of reactor suitable for such a type of coupling is the heat exchanger reactor. In this work, a one-dimensional pseudo-homogeneous plug flow model is used to analyze and compare the performance of co-current and counter-current heat exchanger reactors. A parametric analysis is carried out to address the vital issues, such as the exit conversion of the endothermic reaction, the temperature peak (hot spot) of the exothermic reaction and the reactor volumetric productivity. The measures to reduce the hot spot by different catalyst profiling techniques are also addressed. Some features of the dynamic behavior exhibited by these reactors, which are important from design, operational and control point of view, are presented.     

Conductance measurements of some electrolytes in N,N-dimethyformamide and its binary mixtures witth other organic solvents—II

Equivalent conductances of Bu₄NBPh₄, Bu₄NNO₃, Bu₄NI,KClO₄, Kl, NaI, NaBPh₄, Ph₄PCl, LiCl, AgNO₃ and CuClO₄. 4AN have been measured at 25°C in binary mixtures of N,N-dimethylformamide (DMF) containing 1 mol % of 1, 1, 3, 3-tetramethylurea (TMU), dimethylsulphoxide (DMSO) and hexamethylphosphotriamide (HMPT). Such measurements for LiCl, NaI, KClO₄ and CuClO₄. 4AN have also been carried out in DMF and in binary mixtures of DMF containing 1 mol % pyridine (Py), α-picoline (α-Pic), β-picoline (β-Pic), γ-picoline (γ-Pic) and acetonitrile (AN). The conductance data in all the cases have been analyzed by the Shedlovsky equation. Limiting ion conductances have been obtained by the method of Fuoss et al. The actual solvated radii of ions, evaluated using limiting ion conductances show that Ag⁺ and Cu₊ have strong preferential solvation by all solvents which have been used to prepare the binary mixtures with DMF and the preferential solvation for both Ag⁺ and Cu⁺ with HMPT, DMSO and TMU is relatively stronger than with AN and is practically of similar magnitude as with the organic bases.     

A sample holder for determining material properties

The determination of material properties, such as thermal conductivity, for use in fire models requires precise knowledge of all heat losses. For example, the ignition and subsequent burning of solid samples is sensitive to heat losses from the rear surface of the tested sample. The heat loss depends on the sample holder and its environment. Theoretical predictions of ignition and pyrolysis in standard flammability apparatuses show that the construction of the sample holder has a surprisingly large effect on measured properties especially for thermally thin samples. This makes flammability measurements and inferred thermal properties apparatus dependent. For example, ignition measurements of 6.4 mm (1/4″) plywood samples show a 40% reduction in the critical heat flux for ignition. The back and sides of the sample were sealed by wrapping it with aluminium foil tape. Heat losses from the sample were minimized by placing it on a sample holder having four layers of 3.2 mm (1/8″) thick insulating ceramic paper surrounded by an outer layer of aluminium tape. A detailed mathematical model is developed to fully characterize the thermal response of a sample to a prescribed heat flux in a standard flammability apparatus. The model is used to estimate the residual heat losses not eliminated by the sample holder. Model predictions accurately track the temperature response of blackened brass plates of different thicknesses exposed to several different incident heat fluxes. Brass, of course, has well known thermophysical properties; so, it also provides an excellent means for in situ calibration of the incident heat fluxes. Copyright © 2000 John Wiley & Sons, Ltd.     

Properties of densified amorphous polystyrene

Atactic polystyrene was subjected to an elevated pressure–temperature cycle with the resulting densification, mechanical properties, and thermal scanning behavior observed. Most densifications were carried out with the PST as a viscous liquid. In this manner, ambient residual compactions greater than 2% were produced. Pressures up to 90,000 psi and temperatures to 320°C were employed. The technique used for vitrification from the high pressure–temperature region was found to drastically affect the mechanical behavior. If the polystyrene was vitrified from the treatment region by lowering the temperature, the material exhibited enhanced yield strength, by up to 40%. If the polystyrene was quenched by raising the pressure, the samples exhibited much lower mechanical strength. While the mechanical behavior of temperature-vitrified samples is enhanced compared to the pressure-vitrified materials, their densities are comparable. The compaction achieved is primarily determined by the pressure applied as the polymer vitrifies. Thermal scanning behavior of the pressure-vitrified materials show endothermic and exothermic responses below T_g, while the temperature-vitrified materials do not. Annealing the compacted polystyrene at room temperature caused little change in density. However, at temperatures above 60°C, the density relaxed rapidly. Samples which had been temperature vitrified and annealed such that the compaction completely relaxed, still maintained the enhanced mechanical properties of the densified materials.     

Condensed Phase Behavior in the Combustion of Ammonium Dinitramide

This paper reports on the thermal and combustion behaviors of ammonium dinitramide (ADN). The thermal behavior is measured by a pressure thermogravimetric analysis (TGA) at pressures below 8 MPa. The burning rates of pure ADN and ADN/ammonium nitrate (AN) mixtures are measured in the range 0.2–12 MPa, and the burning temperature profiles are obtained using thermocouples with diameters of 5 and 25 μm. This report mainly focuses on the condensed‐phase behavior in the vicinity of a burning surface. The temperature profiles are complicated because the ADN decomposition and AN dissociation compete during the condensed phase, and the bubbles of the decomposition gas and gas‐phase flame also affect the surface temperature. AN addition helps to understand the effects of AN during the condensed phase, and it was shown that the burning temperature rises to the critical temperature of AN. Based on these experimental results, the pressure dependency of the burning rates is also discussed.     

Permeation of mixtures of organic liquids through polymeric membranes: Role of liquid–liquid interactions

The permeation of pure organic liquids and mixtures of organic liquids through commercial butyl, neoprene, and nitrile membranes was studied using dynamic material deformation (swelling) and permeation techniques. The derived parameters, the breakthrough time (t_BT), steady‐state permeation rate (SSPR), and initial swelling rate (SR), show deviations from additivity for the mixtures, based on the parameters of the pure liquids on a mol fraction basis. In the majority of cases for the three membranes examined, the deviations are independent of the nature of the membranes, and the signs of the deviations for t_BT are opposite to those for SSPR or SR, provided that the membranes are not degraded by one of the solvents. An approach that considers only solvent–solvent interactions based on the enthalpy of mixing was used to predict deviations for mixtures. For mixtures where the enthalpy of mixing is large and exothermic, the permeation of the mixture is less than expected, while for systems where the enthalpy of mixing is large and endothermic, the permeation is larger than expected. A simple semiempirical model predicts the sign and magnitude of the permeation of 73% of the system–permeation property combinations investigated, which show significant deviations from ideality. It is interesting to note that the wrong predictions are for systems where the predictions are positive, that is, for SSPR and SR rates with endothermic systems and for t_BT with exothermic systems. The exceptions also seem to be for systems that correspond to materials having a high resistance to one of the solvents and a very low resistance to the other solvent. Examples of ternary–mixture permeation data are also given and show that, even if two of the pure components do not permeate through a membrane, the membrane will offer little protection if the third component shows a high affinity for the membrane and if the enthalpies of mixing of this component with the other liquids are endothermic. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 195–215, 2002     

Effect of LCP and rPET as reinforcing materials on rheology,morphology, and thermal properties of in situ microfibrillar‐reinforced elastomer composites

Microfibrillar‐reinforced elastomer composites based on two dispersed phases, liquid crystalline polymer (LCP) and recycled poly(ethylene terephthalate)(rPET), and styrene‐(ethylene butylene)‐styrene (SEBS) were prepared using extrusion process. The rheological behavior, morphology, and thermal stability of SEBS/LCP and SEBS/rPET blends containing various dispersed phase contents were investigated. All blends and LCP exhibited shear thinning behavior, whereas Newtonian fluid behavior was observed for rPET. The incorporation of both LCP and rPET into SEBS significantly improved the processability by bringing down the melt viscosity of the blend system. The fibrillation of LCP dispersed phase was clearly observed in as‐extruded strand with addition of LCP up to 20–30 wt %. Although the viscosity ratio of SEBS/rPET system is very low (0.03), rPET domains mostly appeared as droplets in as‐extruded strand. The results obtained from thermogravimetric analysis suggested that an addition of LCP and rPET into the elastomer matrix improved the thermal resistance significantly in air but not in nitrogen. The simultaneous DSC profiles revealed that the thermal degradation of all polymers examined were endothermic and exothermic in nitrogen and in air, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A comparison of conventional and optimized thermally coupled reactors for Fischer–Tropsch synthesis in GTL technology

In this research, the conditions at which a thermally coupled reactor – containing the Fischer–Tropsch synthesis reactions and the dehydrogenation of cyclohexane – operates have been optimized using differential evolution (DE) method. The proposed reactor is a heat exchanger reactor consists of two fixed bed of catalysts separated by the tube wall with the ability to transfer the produced heat from the exothermic side to the endothermic side. This system can perform the exothermic Fischer–Tropsch (F–T) reactions and the endothermic reaction of cyclohexane dehydrogenation to benzene simultaneously which can save energy and improve the reactions' thermal efficiency. The objective of the research is to optimize the operating conditions to maximize the gasoline (C₅⁺) production yield in the reactor's outlet as a desired product. The temperature distribution limit along the reactor to prevent the quick deactivation of the catalysts by sintering at both sides has been considered in the optimization process. The optimization results show a desirable progress compared with the conventional single stage reactor. Optimal inlet molar flow rate and inlet temperature of exothermic and endothermic sides and pressure of exothermic side have been calculated within the practicable range of temperature and pressure for both sides.     

Combustion synthesis of titanium aluminides via co-reduction of oxides

In this study, Ti-50Al and Ti-48Al-2Cr powders were produced via reduction of TiO₂/Al₂O₃ and TiO₂/Al₂O₃/Cr₂O₃ mixtures with Ca. Upon addition of KClO₄ to the above mixtures, a combustion synthesis process was initiated in the systems. In the presence of KClO₄, the reduction temperature decreased from 1000 to 550°C.      

不同聚丙烯发泡体系的挤出发泡行为研究

通过热失重行为研究了不同升温速率对吸热型发泡剂（HP40P）和放热型发泡剂（AC）分解行为的影响；考察了线形聚丙烯（LPP）和长链支化聚丙烯（LCBPP）共混体系（LPP／LCBPP）的挤出发泡行为；制备了LPP／纳米黏土复合材料，并对其进行了挤出发泡研究。结果表明，吸热型发泡剂的分解区间较宽，分解过程平稳，可以作为聚丙烯挤出发泡很好的发泡剂，但需要通过提高螺杆转速来抑制分解过程中的气体损失；LPP／LCBPP／HP40P是良好的聚丙烯挤出发泡体系，可以得到泡孔直径100μm左右、泡孔密度接近106个／cm^2的聚丙烯挤出发泡材料；LPP／纳米黏土复合材料的挤出发泡中并未发生严重的气泡破裂和塌陷现象。动态流变性能研究结果表明该材料表现出很好的熔体弹性，可以作为聚丙烯挤出发泡的良好发泡体系。     

Thermogravimetric and differential thermal analysis of cellulose,hemicellulose, and lignin

The thermal degradation of samples of cellulose, hemicellulose, and lignin have been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) between room temperature and 600°C. The results calculated from static and dynamic TGA indicated that the activation energy E for thermal degradation for different cellulosic, hemicellulose, and lignin samples is in the range 36–60, 15–26, and 13–19 kcal/mole, respectively. DTA of all the wood components studied showed an endothermic tendency around 100°C in an atmosphere of flowing nitrogen and stationary air. However, in the presence of flowing oxygen this endothermic effect was absent. In the active pyrolysis temperature range in flowing nitrogen and stationary air atmospheres, thermal degradation of Avicel cellulose occurred via a sharp endothermic and a sharp exothermic process, the endothermic nadir and exothermic peak being at 320° and 360°C, respectively. In the presence of oxygen, combustion of Avicel cellulose occurred via two sharp exothermic processes. DTA studies of different cellulose samples in the presence of air showed that the shape of the curve depends on the sources from which the samples were prepared as well as on the presence of noncellulosic impurities. Potassium xylan recorded a sharp exothermic peak at 290°C in a nitrogen atmosphere, and in a stationary air atmosphere it yielded an additional peak at 410°C, while in the presence of oxygen the curve showed two sharp exothermic peaks. DTA traces of periodate lignin in flowing nitrogen and air were the same and showed two exothermic peaks at 320° and 410°C, while in the presence of oxygen there were two exothermic peaks in the temperature range 200°–500°C.     

Phase properties of mixtures of ceramides

Ceramides have been proposed to have a central role in the function of the stratum corneum. Ceramides also influence the phase properties of model skin lipid mixtures, but the relevance of this to the stratum corneum function is controversial. Because the stratum corneum contains several classes of ceramides, the type of ceramides used in model mixtures of stratum corneum lipid lamellae may be important. Thus, the properties of α-hydroxy fatty acid containing (HFAC) and nonhydroxy fatty acid containing (NFAC) ceramides and their mixtures have been investigated. Ceramides were obtained by the conversion of purified bovine brain cerebrosides. Isolated, anhydrous HFAC underwent an endothermic solid to liquid transition at 92°C. With hydration, an endothermic transition at 71.8°C was observed which was accompanied by a reduction in the birefringence. The enthalpy increased from 66 to 89 J/g with a 20-d storage time. These thermal properties are very similar to those observed with hydroxy fatty acid containing cerebrosides. In contrast, anhydrous nonhydroxy fatty acid containing ceramides underwent a broad endothermic transition over the temperature range of 50–90°C. When hydrated, the initial endothermic transition was interrupted by an exothermic transition that was followed immediately by a second endothermic transition. During these thermal changes, there was a loss of birefringence, and with completion of the second endothermic transition, a nonbirefringent liquid was observed. NFAC samples, stored at 70°C for 5 min, cooled, and then rescanned, displayed only one endotherm at 75°C. The thermal behavior of mixtures of HFAC and NFAC was relatively simple, with a progressive decrease and broadening in the temperature of the phase transition as the proportion of NFAC increased up to weight fractions of NFAC of 0.7. At lower weight fractions, a plateau in thetransition temperature as a function of weight fraction was observed. Even at a weight fraction of 0.1 HFAC, no transition to a nonbirefringent liquid state was observed. The high enthalpic changes observed with mixtures of HFAC and NFAC are consistent with the proposed central role that ceramides have in the mechanical and permeability properties of the skin. Moreover, the marked difference in the properties of these two similar lipids may help to explain some of the properties of the stratum corneum.