Black powder thermal ignition

A terpene inhibitor is usually added to the monomer to prevent spontaneous polymerisation, and in its absence, the monomer will spontaneously explode at pressures above 2.7 bar. The inhibited monomer will explode if ignited [1]. Explosion under thermal initiation is now held to be a disproportionation, that to tetrafluo-romethane and carbon gives 3.2 kJ/g, the same energy as black powder [3], Liquid tetrafluoroethylene, being collected in a liquid nitrogen-cooled trap open to air, formed a peroxidic polymer which exploded [2]. 

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. 

IFF (molecular weight 100.02) is a colorless, tasteless, odorless nontoxic gas.11 It is stored as a liquid (its vapor pressure at -20°C is 1 MPa) and polymerized usually above its critical temperature of 33.3°C (91.9°F) and below its critical pressure 3.94 MPa (571 psi). The polymerization reaction is exothermic. In the absence of air it disproportionates violently to yield carbon and carbon tetrafluo-ride. This reaction generates the same amount of energy as an explosion of black powder. The decomposition is initiated thermally therefore, the equipment used in handling and polymerization of IFF has to be without hot spots. The flammability limits are 14 to 43% TFE bums when mixed with air and forms explosive mixtures with air and oxygen. The ignition temperature is 600 to 800°C (1112 to 1472°F).12 When stored in steel cylinder it has to be under controlled conditions and with a suitable inhibitor. 

Reliable ignitibility itself from a small thermal impulse, such as a fuse, black powder, or a primer. The ignition temperature of a first fire should be 500°C or less for best results. 

The UD3 is a brown-black, spontaneously igniting powder. To prepare very pure Dg, it is thermally decomposed either at atmospheric or reduced pressure (see also Hg above 111). The U... 

---