Application of heat conduction calorimetry to high explosives

This paper describes some thermal analysis experiments conducted on high explosive samples. These employ differential scanning calorimetry to monitor thermal effects at elevated temperatures (around 200 °C) and heat conduction calorimetry to record thermal effects at much lower temperatures (below 100 °C).The work shows that, due to the generally high thermal stability of many high explosive compositions, heat generation rates are very low, if detectable at all, at normal storage temperatures, even when using a very sensitive instrument. The sensitivity and reproducibility of this technique has been investigated in detail by Wilker et al. [S. Wilker, U. Ticmanis, G. Pantel, Detailed investigation of sensitivity and reproducibility of heat flow calorimetry, in: Proceedings of the 11th Symposium on Chemical Problems Connected with the Stability of Explosives, Sweden, 1998] and shown to be capable of recording heat generation rates of less than a microwatt. This allows continuous measurement of decomposition processes in nitrate ester based propellants at temperatures as low as 40 °C. However, the measurement of very low levels of heat generation is difficult, time consuming and therefore expensive. If the assumption is made that the life limiting process is invariably the slow decomposition of the energetic component, this will frequently lead to very long service lifetime predictions.A number of possible complications are identified. Firstly, due to its low detection threshold, a heat conduction calorimeter may detect other reactions which will not lead to failure, but which may still dominate the heat flow signal. Secondly, the true failure process may generate little energy and be overlooked. In view of these considerations, at present it seems unwise to rely on heat conduction microcalorimetry as the only tool for the assessment of the life of high explosive energetic systems.Based on examples of life terminating processes in high explosives during storage and use, it is clear that decomposition of the energetic material is not invariably the cause of system failure. It is also by no means the only reaction that may take place in, and be observed by, a heat conduction calorimeter.     

Biodegradation analyses of trichloroethylene (TCE) by bacteria and its use for biosensing of TCE

Trichloroethylene (TCE) is a toxic, recalcitrant groundwater pollutant. TCE-degrading microorganisms were isolated from various environments. The aerobic bacteria isolated from toluene- and tryptophan-containing media were Pseudomonas sp. strain ASA86 and Burkholderia sp. strain TAM17, respectively; these are necessary for inducing TCE biodegradation in a selective medium. The half-degradation time of TCE to a concentration of 1 mg/L was 18 h for strain ASA86 and 7 days for strain TAM17. While identifying toluene/TCE degradation genes, we found that in strain ASA86, the gene was the same as the todC1 gene product encoding toluene dioxygenase identified in Pseudomonas putida F1, and that in strain TAM17, the gene was similar to the tecA1 gene product encoding chlorobenzene dioxygenase identified in Burkholderia sp. PS12. A novel TCE biosensor was developed using strain ASA86 as the inducer of toluene under aerobic conditions. The TCE biosensor exhibited a linear relationship below 3 ppm TCE. Detection limit of the biosensor was 0.05 ppm TCE. The response time of the biosensor was less than 10 min. The biosensor response displayed a constant level during a 2 day period. The TCE biosensor displayed sufficient sensitivity for monitoring TCE in environmental systems.     

基于TAM理论的顾客心理契约形成机理研究——B2C情景下的实证研究

基于TAM理论研究了B2C情景下顾客心理契约的形成机理。通过相关文献评述,提出了B2C情景下顾客心理契约形成机理模型及假设,通过实证分析验证模型及假设。结果表明:感知易用和感知风险对感知有用具有显著的影响作用;感知有用以及感知易用通过顾客价值观/态度对顾客心理契约具有显著的影响;同时,感知风险和感知易用对顾客心理契约具有显著的直接影响作用。研究结论对B2C情景下服务商保持和维护客户关系具有积极作用,为网络商家建立积极地调控干预机制,促进顾客心理契约正效应感知提供参考。     

Comparison of thermal polymerization mechanisms for α-methylstyrene and <Emphasis Type="Italic">trans</Emphasis>-β-methylstyrene

The polymerization mechanisms of styrene and various derivatives by α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) were evaluated. Experiments were carried out for dimerization identification and thermal polymerization estimation by differential scanning calorimetry (DSC), thermal activity monitor (TAM) and Fourier transform infrared absorption spectrophotometer (FTIR). The results show that, under temperature ranges of 60–190 and 50–170°C, AMS and TBMS performed dimerization by benzene ring and ethylene double bond, respectively. AMS and TBMS would form unsaturated dimers, saturated dimers and trimers, etc., during the period of thermal polymerization. Through this study, one can estimate possible intermediates of the polymerization process for the monomer of interest in the petrochemical industry.     

Thermal runaway evaluation of α-methylstyrene and trans-β-methylstyrene with benzaldehyde

Styrene is an important chemical in the petrochemical industry. In recent years, there have been sporadic releases, runaway reactions, fires, and thermal explosion accidents incurred by styrene and its derivatives worldwide. The purpose of this study was to estimate the impact of styrene and its derivatives of α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) contacting with benzaldehyde. Experiments were carried out to evaluate the thermokinetic parameters estimated by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III). TAM III was used to determine the fundamental thermokinetics under various isothermal temperatures, 80, 90 and 100°C. This autocatalytic reaction was demonstrated in thermal curves. After styrene was contacted with benzaldehyde, the exothermic onset temperature (T ₀) and the total heat of reaction (Q _total) were altered by DSC tests. When benzaldehyde is mixed with AMS and TBMS, the reaction time will be shorter but the enthalpy reduced, as revealed by TAM III tests. As AMS and TBMS, respectively, were contacted with benzaldehyde, both exothermic phenomena were changed during the reaction excursion. According to the results of this research, an operator should dictate the oxygen concentration in order to avoid any potential hazards during handling and transportation.     

Reaction hazard analysis for cumene hydroperoxide with sodium hydroxide or sulfuric acid

Organic peroxides (OPs) are very susceptible to thermal sources, chemical pollutants or even mechanical shock. Over the years, they have caused many serious explosions. Cumene hydroperoxide (CHP) is widely employed to produce phenol and dicumyl peroxide (DCPO) in the manufacturing process. Differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were employed to determine the potential thermal hazards and thermokinetic parameters (such as exothermic onset temperature (T ₀), maximum temperature (T _max), and enthalpy (ΔH)) of CHP mixed with sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄). High performance liquid chromatography (HPLC) was used to analyze the concentration vs. time of CHP.When CHP is mixed with NaOH, the T ₀ is induced earlier and reactions become more intricate than the pure CHP solution. CHP added to NaOH or H₂SO₄ is more dangerous than pure CHP alone. Depending on the operating conditions, NaOH and H₂SO₄ are the incompatible chemicals for CHP.     

Runaway effects of nitric acid on methyl ethyl ketone peroxide by TAM III tests

Methyl ethyl ketone peroxide (MEKPO) is an unstable material above certain limits of temperature, decomposing into chain reactions by radicals. The influence of runaway reactions on this basic characteristic was assessed by evaluating kinetic parameters, such as activation energy (E _a ), frequency factor (A), etc., by thermal activity monitor III (TAM III). This was done under three isothermal conditions of 70, 80, and 90 °C, with MEKPO 31 mass% combined with nitric acid (HNO₃ 6 N) and sodium nitrate (NaNO₃ 6 N). Nitric acid mixed with MEKPO gave the maximum heat of reaction (△H _d ) and also induced serious reactions in the initial stage of exothermic process under the three isothermal temperatures. The time to maximum rate (TMR) also decreased when HNO₃ was mixed with MEKPO. Thus, MEKPO combined with HNO₃ 6 N forms a very hazardous mixture. Results of this study will be provided to relevant plants for alerting their staff on adopting best practices in emergency response or accident control.     

Automatic and adaptive calibration of 3D field sensors

Embedded sensors are an emerging trend in mobile consumer devices. Calibration of the sensors in this environment can be prohibitively difficult for the user. We propose an automatic calibration algorithm that can be used for any three-dimensional sensor sensing some external field. In particular, it is suitable for calibrating a three-axis magnetometer. The algorithm is based on recursive fitting of an ellipsoid to collected samples from the sensor. It can adaptively update the calibration parameters and is completely invisible to the user.     

Novel stilbene‐based Fischer base analog of leuco‐TAM – (2E,2′Z)‐{2‐(4‐(E)‐styrylphenyl)propane‐1,3‐diylidene}bis(1,3,3‐trimethylindoline) – derivatives: synthesis and structural consideration by 1D NMR and 2D NMR spectroscopy

We report the synthesis of a series of novel stilbene‐based (St) Fischer base analogs of leuco‐triarylmethane (LTAM) dyes by treating Fischer base with (E)‐4‐styrylbenzaldehyde derivatives. All St‐LTAM molecules examined herein are characterized by 1D and 2D NMR. They were found to exhibit ZE configuration and isomerize to their diastereomers EE and ZZ in 2–3 h. They exhibit type I behavior of diastereomeric isomerization. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermokinetics evaluation and simulations for the polymerization of styrene in the presence of various inhibitor concentrations

Styrene is an important commodity chemical that is globally applied in various polymerization processes. The aim of this study was to obtain integrated thermokinetics and safety parameters for polymerization of styrene. We mainly used differential scanning calorimetry (DSC), thermal activity monitor (TAM), and simulative methods to investigate thermal polymerization of styrene and styrene containing various levels of 4-tertiary-butylcatechol (TBC). The results obtained included the rate constant (k), reaction order (n), apparent activation energy (E _a), frequency factor (A), and so on, from various DSC curves and simulative methods. From DSC curves, the exothermic onset temperature (T ₀) was about 105 and 132°C for styrene and styrene containing 10 ppm TBC. On the other hand, the test results from TAM indicated that styrene polymerization displays an autocatalytic phenomenon from 50–85°C. By means of this study, the intrinsic safety of a system for styrene during transportation and storage could be established.