Thermal Decomposition and Burning Rate

A thermally degraded GAP copolymer is produced at 532 K, accompanied by 3 = 0.25, where 3 is the mass fraction loss obtained by thermal degradation.The ex- 

Infrared analysis of GAP copolymer before and after thermal degradation monitored by TG shows that the absorption of die azide bond of the starting GAP copolymer (P = 0.0) is seen at about v = 2150 cm fI This azide bond absorption is completely lost following thermal degradation (P = 0.41). The -N3 bonds within the GAP copolymer decompose thermally above 537 K to produce Nj. Thus, the gasification of the GAP copolymer observed as the first reaction stage occurs due to spHt- 

The burning rate of GAP copolymer increases linearly with increasing pressure in an In rversus Inp plot, as shown in Fig. 5.17. The pressure exponent of burning rateat a constant initial temperature, as defined in Eq. (3.71), is 0.44. The temperature sensitivity of burning rate at constant pressure, as defined in Eq. (3.73), is 0.010 K h 

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Ellis and coworkers studied the effect of lead oxide on the thermal decomposition of ethyl nitrate vapor.P l They proposed that the surface provided by the presence of a small amount of PbO particles could retard the burning rate due to the quenching of radicals. However, the presence of a copper surface accelerates the thermal decomposition of ethyl nitrate, and the rate of the decomposition process is controlled by a reaction step involving the NO2 molecule. Hoare and coworkers studied the inhibitory effect of lead oxide on hydrocarbon oxidation in a vessel coated with a thin fQm of PbO.P l They suggested that the process of aldehyde oxidation by the PbO played an important role. A similar result was found in that lead oxide acts as a powerful inhibitor in suppressing cool flames and low-temperature ignitions.P l... 

At temperatures below the ignition point, the thermal decomposition of black powder provides an interesting insight into the processes which are thought to control the reaction rate during subsequent burning. In decomposition experiments it has been shown that the overall reaction proceeds in several steps. As the temperature is increased the steps become shorter and the reaction faster. Since these reactions involve gases, the effect of pressure is also important. 

A study was conducted to find out the effect of addition of these nitroplasticizers on ballistic properties of AP and RDX/HMX filled CMDB propellants. The data generated clearly indicated that the incorporation of nitroplasticizer, that is, 1 1 mixture of BDNPF and BDNPA in place of diethyl phthalate (DEP) for AP and nitramine based CMDB propellants improved the burn rates as well as /sp and thermal decomposition behavior of these propellant formulations [193]. 

Al Fakir, M. S., Progr. Astronaut. Aeronaut., 1981, 76, 5512—564 Admixture of lithium perchlorate [1] or zinc perchlorate [2] leads to decomposition with explosion at 290° or ignition at 240°C, respectively. The role of ammine derivatives of lithium and magnesium perchlorates in catalysing the thermal decomposition of ammonium perchlorate has been studied [3], and lithium perchlorate has a strong catalytic effect on the burning rate [4]. 

ITC heating of Iclryl increases the rate of burning of the substance. Tlus was already shown by Andreev (V ol. Ill, Fig. 6), by his later work [94J and substantiated by M. M. Jones and Jackson [87] and Japanese authors [86). Tire latter authors found for example that preheating the sample to 180 C lowers its ni.p. by 20 C and the decomposition temperature by 12 C. They also examined the samples of tetryl heated at 165°C for 3 hours by liquid chromatography, by TLC, NMR and mass specirography. They found that 2,4.6-trinitroanisol and picric acid are fonned on the thermal decomposition of tetryl at I60--200 C. 

Burning of tetryl is discussed in the monograph by Glazkova [92] and reference is given to the early work of Hinshelwood [93] who pointed out that thermal decomposition of tetryl produces picric acid which plays the part of a catalyst of the decomposition. The rate of burning of tetryl under pressure increases by addition of potassium bichromate, according to Glazkova [92]. 

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