Deflagrating substances/mixtures

From these three sources of information the peak value of the rate of pressure increase due to deflagration of mixtures of oxidizers and flammable substances is given at the maximum heat of reaction, and a similarity is found between the open systems in the IMO combustion rate test and the partially enclosed systems in the TNO deflagration test. 

Aluminum in the form of finely divided dusts is flammable. The dusts form explosive mixtures with air. Aluminum powder is a component of many explosives. It is used in many explosive compositions, combined with ammonium nitrate or nitroguani-dine, for example (see Chapter 40). When combined with aluminum, many deflagrating substances attain detonation brisance. 

The first aim of a thermal stability screening test (e.g., DSC/DTA) is to obtain data on the potential for exothermic decomposition and on the enthalpy of decomposition (AHd). These data, together with the initial theoretical hazard evaluation, are used in reviewing the energetic properties of the substance (Box 4) and the detonation and deflagration hazards of the substance (Boxes 7 and 8). The screening tests also provide data on the thermal stability of the substance or mixture, on the runaway potential, on the oxidation properties, and to a lesser extent, on the kinetics of the reaction (Box 10). 

A substance or mixture is potentially capable of deflagration if it has a AHd greater than 250 cal/g (-1000 J/g), a "yes" in Box 8. Deflagration tests (Box 7) then should be carried out as well as tests for sensitivity to impact and friction. 

In attempts to increase the detonability of Ni hydrazinate, it was mixed with equal parts of an easily ignitable initiating substance, such as Pb-styphnate or Pb-picrate, and then ignited. The best that could be obtained was a deflagration but no detonation. Mixtures of the Ni complex with RDX deflagrated and only in one case detonated (Ref 3) ... 

The possibility of a deflagration-to-detonation transition (DDT) exists if a large quantity of a self-reactive substance is burned. Non—detonatable substance do not display this hazard. The possibility of detonation can be evaluated by the 50/60 steel tube test. We have performed a 50/60 steel tube test for mixtures of crystalline potassium perchlorate and HCH with large—sized sawdust. The result are shown in Table 3.19 and Fig.3.32. 

By the use of the improved time/pressure testing rig, an assessment of the hazard of deflagration has been made for a series of chemicals as mixtures of oxidizers and flammable substances, 8 2 8 a 8 8 ( explosives 88 ) 0 and organic peroxides 8 3 8 81. Many of the compounds evaluated in these tests are solids, and it is thought that the hazard associated with deflagration may be affected by the granular size of the samples tested. It is, therefore, important to determine if the size of the grains affects the test results. 

Factors affected by the rate of pressure increase in a given space and for a given amount of energy include the pressure reached at equilibrium per unit amount of substance, and the reaction rate (or deflagration rate). The improved time/pressure test method is considered to be the test method that satisfies both constraints. In the case of having a clear flame front like KCIO 3 /cellulose mixtures, the deflagration rate can be obtained by the method discussed above. 

By incorporating in the proplnt organic nonexplosive substances, such as cellulose, vaseline, cellulose acetate, urea, hydrocellulose, Centralites, stearic acid etc, which alter the compn of die gas mixture produced by the deflagrating proplnt by appreciably increasing the number of mols of gas formed, thus lowering the temp by "dilution ... 

Deflagrating, adj. Applied to a spoon in which deflagration occurs. Sometimes applied to a mixture, or to a single substance. 

A self-reactive substance or mixture is regarded as possessing explosive properties when in laboratory testing the formulation is liable to detonate, to deflagrate rapidly or to show a violent effect when heated under confinement. 

---