Combustion and thermal decomposition characteristics of composite solid propellan

The role of thermal decomposition of the binder and the oxidiser in the thermal decomposition, ageing and combustion of composite solid-propellants has been investigated. The present study shows that the burning rate and ageing of polystyrene and ammonium perchlorate propellant are related to the thermal decomposition of the propellant itself and ammonium perchlorate.     

硫化氢热分解制氢过程的化学动力学研究

采用化学热平衡分析方法研究了硫化氢热分解制氢过程,研究了硫化氢在不同温度和体积分数下的分解过程,并与试验数据进行了比较。结果表明,基元反应机理能较好地模拟硫化氢热分解制氢过程。硫化氢的热分解率依赖于反应温度,高温下能获得较好的分解制氢效果;温度较低时,时间是硫化氢趋于平衡的主要影响因素,随着温度的提高,温度成为影响硫化氢趋于平衡的主要影响因素。硫化氢初始体积分数对热分解制氢反应具有较大的影响,采用较低体积分数的硫化氢混合气有利于获得高的硫化氢热分解制氢率。     

Effect of catocene on the thermal decomposition of ammonium perchlorate and octogen

Simultaneous TG/DSC-FT-IR was employed to study the effect of catocene with a high concentration (5, 15, and 25 %) on the thermal decomposition of ammonium perchlorate (AP) and octogen (HMX) with different particle sizes. The experimental results show that catocene has effect on the thermal decomposition of AP and HMX, but the role that catocene playing changes with the concentration of catocene and the particle size of AP and HMX. High concentration of catocene (more than 15 %) benefits the decomposition of fine AP and HMX at low temperature, but has little effect on the decomposition of median and coarse AP. The thermal decomposition of HMX is affected by catocene mainly through increasing the heat release of the first decomposition step, while through both increasing the heat release and decreasing the decomposition temperature of the first decomposition step for the thermal decomposition of AP.     

Controlled rate thermal analysis of hydromagnesite

The reaction of magnesium minerals such as brucite with CO₂ is important in the sequestration of CO₂. The study of the thermal stability of hydromagnesite and diagenetically related compounds is of fundamental importance to this sequestration. The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO₂. This work makes a comparison of the dynamic and controlled rate thermal analysis of hydromagnesite and nesquehonite. The dynamic thermal analysis of synthetic hydromagnesite proves that dehydration takes place in two steps at 135 and 184°C, dehydroxylation at 412°C and decarbonation at 474°C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145°C, respectively. In the CRTA experiment both water and carbon dioxide are evolved in an isothermal decomposition at 376°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of non-isothermal nature reveal partial nesquehonite structure.     

Non-isothermal kinetic studies on thermal decomposition of energetic materials

Thermal stability and decomposition kinetics for two energetic materials, potassium nitroform (KNF) and 5-Nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO), were investigated to obtain information on their safety for handling, storage, and use. Differential scanning calorimetry (DSC) and simultaneous thermogravimetry-differential thermal analysis (TG-DTA) techniques have been used to study thermal behavior of these energetic compounds. The results of TG analysis revealed that the main thermal degradation for the KNF occurs during two temperature ranges of 270?C330 and 360?C430?°C. Meanwhile, NTO decomposes completely in temperature range of 250?C300 °C. TG-DTA analysis of KNF indicates that this energetic compound dehydrated (at about 108?°C) before its decomposition. However, NTO is thermally stable until its decomposition. The decomposition kinetic of energetic materials was studied by non-isothermal DSC under various heating rates. Kinetic parameters such as activation energy and frequency factor for thermal decomposition of energetic compounds were obtained via the methods proposed by ASTM E696 and Starink. Also, thermodynamic parameters correspond to the activation of thermal decomposition and critical ignition temperatures of the compounds were obtained.     

A thermal decomposition study of polymers by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

The thermal decomposition of polymers (poly(vinyl chloride) (PVC) and polystyrene (PS)) has been studied with synchrotron VUV photoionization mass spectrometry at low pressure. Pyrolysis products formed at different temperatures have been identified by the measurement of photoionization mass spectra at different photon energies. The experimental results demonstrate the variation of the pyrolysis product pool of PVC at different temperatures, dividing the thermal decomposition process into two stages: the low‐temperature stage to form HCl and benzene, and the high‐temperature stage to form numerous large aromatic hydrocarbons. For the thermal decomposition of PS, four reaction categories are determined. This work reports a new application of synchrotron VUV photoionization mass spectrometry in the study of the thermal decomposition of polymers, and demonstrates its good performance in product analysis, which is expected to help understand the thermal decomposition mechanism of PVC, PS and other synthesized polymers. Copyright © 2009 John Wiley & Sons, Ltd.     

Mechanisms of thermal decomposition in totally aromatic polyurethanes

The primary fragmentation mechanisms in the thermal decomposition of polyurethanes were studied in detail by direct pyrolysis into the mass spectrometer. The remarkable difference in the thermal stability of the two totally aromatic polyurethanes I and II (Fig. 1) reflects their different decomposition pathways. In fact, polymer I undergoes a depolycondensation process that yields diiscyanate and dialcohol as primary thermal fragments. The thermal decomposition of polymer II proceeds instead via the formation of a cyclic compound that has been isolated and characterized. In contrast, open-chain fragments are generated in the thermal decomposition of the partially aliphatic polymer III.     

In situ thermal decomposition of starch with constant moisture in a sealed system

This paper reports a DSC study of the thermal decomposition of starch kept at constant moisture content (0-50%) in a sealed system comprising a high-pressure stainless steel pan with a gold-plated copper seal. The advantage of this technique is that it facilitates the detection and study of the processes of thermal decomposition of starch with constant moisture content, which is a common scenario in the processing of thermoplastic starches. It was found that the decomposition temperature decreased with increasing water content, and that the peak in decomposition temperature broadened, which is different to the case observed in open, unsealed systems.     

Kinetics of thermal decomposition of nickel sulfate hexahydrate

The paper describes the kinetics of all the recorded steps of thermal decomposition of nickel sulfate hexahydrate in air. The thermal decomposition of the salt in air led to NiO at about 1060 K. The kinetic parameters, the activation energyE and the preexponential factorA, and the thermodynamic parameters, the entropy, enthalpy and free energy of activation were evaluated for the dehydration and decomposition reactions. Tentative reaction mechanisms are suggested for each step of the thermal decomposition.     

Kinetics and mechanism of thermal decomposition of copper hypophosphite

On the basis of an elaborate investigation of the thermal decomposition reaction for crystalline copper hypophosphite by kinetic, radiospectroscopic and optical methods, and by a study of the peculiarities of the copper hypophosphite structure and defects, it has been found possible to suggest the mechanisms by which the decomposition kinetics are regulated.     

The effect of alkaline pretreatment on the thermal decomposition of hemp

The goal of this study was to clarify the effect of alkaline pretreatments on the thermal decomposition and composition of industrial hemp (Cannabis sativa L.) samples. Thermogravimetric/mass spectrometric measurements (TG/MS) have been performed, on untreated, hot water washed, and alkali-treated hemp samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. Principal component analysis (PCA) has been used to find statistical correlations between the data. Correlations have been obtained between the parameters of the thermal decomposition and the alkali ion content as well as the altered chemical structure of the samples. The differences in the thermal behavior of the samples are explained by the different K⁺ and Na⁺ contents and the changed structure of the hemicellulose component of the samples due to the pretreatments. The more alkali ions remain in the hemp samples after the alkali treatment, the more ash, char and lower molecular products are formed during thermal decomposition.     

Study of some volatile compounds evolved from the thermal decomposition of atenolol

Simultaneous thermogravimetry–differential scanning calorimetry (TG–DSC) and coupled thermogravimetry–infrared spectroscopy (TG–FTIR) analyses were used to study the antihypertensive drug atenolol. The TG–DSC curves provided information concerning the thermal stability and decomposition profiles of the compound. From the TG–FTIR coupled techniques, it was possible to identify ammonia and isopropylamine as possible volatile compounds released during the thermal decomposition of the drug.     

Mechanism of thermal decomposition of thiourea derivatives

The thermal decomposition of a series of compounds has been studied by thermogravimetry, mass spectrometry, nuclear magnetic resonance and elemental analysis. The combined use of mass spectrometry and thermogravimetry (MS and TG) in the analysis of these compounds has allowed characterization of the fragmentation pattern which was the objective of this research. The gaseous products, volatile condensed products and solid residues were identified by NMR and MS. Based on the product of thermal decomposition, the mechanism of thermal decomposition has been derived.     

新型高能炸药热分解研究进展

炸药的热分解对其安定性和库存可靠性等研究是很重要的。本文总结了国内外有关TNAZ(1,3,3-三硝基氮杂环丁烷)、NTO(3-硝基-1,2,4-三唑-5-酮)、LLM-105(1-氧-2,6-二氨基-3,5-二硝基吡嗪)、FOX-7(1,1-二氨基-2,2-二硝基乙烯)等几种新型高能炸药的热分解研究。分别从理论上、实验上阐述了它们的热分解研究现状,指出了以前研究中存在的问题,预测了钝感高能炸药热分解的发展前景。参考文献32篇。     

氧气的体积分数对N2O热分解的影响

N2O是大气中不可忽视的污染物.目前,世界上所排放的N2O主要有三个来源:一是硝酸工业等化工生产;二是流化床锅炉等煤燃烧设备;三是汽车发动机.由于N2O会导致温室效应和破坏臭氧层,而近年来大气层中N2O的氧气体积分数逐年上升,N2O排放的控制技术受到越来越多的关注[1～4].……     

Identificaiton of potential thermal runaways using small scale thermal analytical techniques

With industry's focus on the early identification of potential thermal runaways in chemical processes, it is important that these potential thermal hazards be identified early in a process' development. Thermal runaways can be initiated in several ways: through an uncontrolled heat of reaction, the initiation of an exothermic decomposition/oxidation, or a combination of these two. It is therefore critical that information on exothermic decomposition/oxidation and heat of reaction be easily obtainable using small scale laboratory reactions.A small scale thermal hazards identification program, using process samples from a 200 ml reaction and small scale thermal analytical techniques, identifies potential thermal runaways rapidly. The small scale thermal hazards identification program utilizes three small scale thermal analytical techniques developed at the Merck Research Laboratories. These include the use of specially designed DSC reusable metal crucibles to identify closed system exothermic activity in process samples, the Small Scale Isothermal Age Technique to accurately determine exothermic onset temperatures and Syringe Injection calorimetry to determine heat of reactions which occur at room temperature.     

The influence of the environment on the thermal decomposition of oxysalts

The environment can influence the thermal decomposition of an oxysalt by;

1. causing a change in the course of chemical decomposition or
2. causing an alteration in the physical nature of the solid product or solid intermediates.

The environment can also effect the equilibrium condition or the course of the kinetics. The use of special techniques such as thermogravimetry, differential thermal analysis, or differential scanning calorimetry to study the decomposition means that a special environment is imposed on the oxysalt and this effects the thermal decomposition process. The influence of the environment in changing the course of a chemical reaction can be illustrated by reference to the decomposition of zinc oxalate and nickel oxalate. The DTA shows that the decompositions are endothermic in inert atmospheres but exothermic in air or oxygen. The reasons are different however in each case. Thus although the product of decomposition of zinc oxalate is zinc oxide the change in character of the decomposition from endothermic to exothermic is due to the catalytic oxidation of carbon monoxide to carbon dioxide in the presence of oxygen. The similar change in the character of nickel oxalate decomposition is however due to nickel formation in an inert atmosphere but nickel oxide in air or oxygen. The alteration in the physical nature of the solid products is illustrated by surface area measurements on solid residues from the decomposition of carbonates or oxalates. The kinetic and chemical equilibrium studies showing the influence of environment are illustrated by reference to dehydration studies, carbonate and oxalate decompositions.     

Effect of zinc chloride on thermal decomposition of polymethacrylic and polyacrylic esters

Zinc chloride reduces the rate of thermal and thermooxidative decompositions of polymethacrylic esters and increases the thermal decomposition rate of polyacrylic esters. Mechanisms of the thermal decompositions of polymethacrylates and polyacrylates in the presence of ZnCl₂ have been suggested.For thermal decomposition polymethacrylic esters, the rate of depolymerization decreases due to the formation of cycles in a polymer chain by reaction of Zinc chloride with neighbouring ester groups. For thermooxidative decomposition of polymethacrylates, ZnCl₂ decreases also the rate of initiation of depolymerization and causes decomposition of hydroperoxide groups by a heterolytic mechanism. The increase in thermal decomposition rate of polyacrylic esters results from the high activity of complexes of ester groups and ZnCl₂ in decomposition reactions with formation of alcohol and CO₂ through Cameron mechanism.     

Kinetics of thermal decomposition of aseptic packages

Kinetics of thermal decomposition of aseptic packages (e.g. Tetrapak cartons) and pyrolysis of this waste in a laboratory flow reactor was studied. Three different models for the calculation of the reaction rate and the determination of apparent kinetic parameters of thermal decomposition were used. The first method assumes a two stage thermal decomposition and the kinetic parameters were determined by fitting a derivative thermogravimetric (DTG) curve to experimentally determined thermogravimetric data of whole aseptic cartons. The second method uses kinetic parameters determined by fitting DTG curves to thermogravimetric data of individual components of aseptic packages. The last method was a multi-curve isoconversion method assuming a change of kinetic parameters with the increasing conversion. All types of the determined kinetic parameters were used in a mathematical model for thermal decomposition of mini briquettes made from aseptic packages at the temperature of 650°C. The model calculated also the heat conduction in the particles and it was verified by an independent set of experiments conducted in a laboratory screw type flow reactor.     

过氧化苯甲酰的热分解研究

The thermal decomposition process of benzoyl peroxide was investigated by Accelerating Rate Calorimeter. The curves of thermal decomposition temperature and pressure versus time for the systems were obtained. The curves of temperature rising-rate versus thermal decomposition temperature were also obtained. After the data revision disposal and analysis processing, thermal decomposition parameters and kinetic data of benzoyl peroxide were calculated, respectively.