Permitted explosive compositions

Explosives which produce a flash on detonation and create hazards for workers in coal mines are called non-permitted explosives. Basically these explosives include compositions based on aluminum powder and other HEMs with negative oxygen balance. 

In 1957 the National Coal Board [83] centralized the purchase of permitted explosives in Great Britain and introduced standardization of composition, cartridge sizes etc. 

Composition and properties of some typical British non-permitted explosives (according to J. Taylor and Gay [4])... 

Recently Imperial Chemical Industries Ltd. developed a class of explosives known unofficially as ultra-safe . The general principle of these compositions is that they contain a higher proportion of cooling salts, ground to a finer size, than is customary with other permitted explosives. They have proved considerably safer than any other permitted explosive. 

C. Permitted explosives, which are divided into 2 subgroups according to their chemical composition ... 

It is important to prevent any deflagration of permitted explosives. Since the deflagration of an explosive proceeds at a much slower rate than its detonation, it may ignite methane-air and coal dust-air mixtures. This must be prevented by using suitable compositions (-> Permitted Explosives) and application techniques. 

Most explosives and pyrotechnical compositions are prepared by a mixture of - Oxidizers and fuels. Fuel means any substance capable of reacting with oxygen and oxgen carriers (oxidizers) with the evolution of heat. Hence, the concept of fuel her has a wider significance than that of fuel in everyday language thus, for instance, ammonium chloride in ion-exchanged -> Permitted Explosives can act as a fuel. 

All explosive materials contain oxygen, which is needed for the explosive reaction to take place. The oxygen can be introduced by chemical reactions (nitration) or by mechanical incorporation of materials containing bound oxygen. The most important solid-state oxidizers are nitrates, especially -> Ammonium Nitrate and -> Sodium Nitrate for explosives -> Potassium Nitrate for -> Black Powder and ion exchanged -> Permitted Explosives, potassium chlorate for -> Chlorate Explosives and for pyrotechnical compositions Ammonium Perchlorate (APC) for -> Composite Propellants. 

Shotfiring in coal mines constitutes a risk in the presence of firedamp and coal dust. Permitted explosives are special compositions which produce short-lived detonation flames and do not ignite methane-air or coal-dust-air mixtures. 

German Permitted Explosives are, as before, divided into three classes. Their composition still remains undisclosed and the method of manufacture is kept secret. 

The composition of typical permitted explosives made in Belgium are given overleaf (Table 105), according to Goffait and Waterlot [119]. The explosives belong to ion exchange group with potassium or sodium nitrate and ammonium chloride. 

TABLE 5.1 Compositions ofNon-permitted Commercial Explosives... 

Compex. One of the Brit "permitted mining expls which are designated as EqS (equivalent in safety to sheathed explosives). It is listed in Ref without giving the composition Ref Taylor Gay (1958), 96... 

In practice one measures explosion limits by permitting a reaction mixture (of fixed composition) to enter a flask at a previously determined higher temperature and observing the minimum pressure at which explosion takes place. If the rate law for the reaction is known (actually this is seldom true) then any of the above equations can be tested. In this way Sagulin showed that the critical explosion pressures for H2 + CI2 mixtures followed an equation of the form... 

Novel catalyst compositions comprising complexes of tin(IV) salts and primary amine compounds allow delay of gelation until they dissociate under certain reaction conditions. Encapsulated catalysts have been used for delayed reaction in production of explosives this delay permits casting of explosives. 

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