Burning rate along the wire

Fig. 13.30 Effect of silver wire diameter on burning rate along the wire, showing that the maximum burning rate is obtained at a diameter of about 0.3 mm.

Figure 9-14. Effect of metal wire on Pressure, MPa burning rate along the wire.

Fig. 13.29 Effect of various metal wires on the burning rate of a propellant along the wires.

Wire Burning Rate Along Wire, in. /sec. Ratio of Burning Rate Along Wires to Standard Ratea Properties of the Metal Thermal Diffusivity Melting at 650° C., Temperature, sq. cm./sec. °C. ... 

A very important observation was recently made by Rurnbcl ( 2]. This is the incorporation of fine metal wires into a propellant, which increase the rate of burning as recorded originally in PVC plastisol propellants 12] but seems to be now a general practice in composite propellants. Metal wires are introduced into the composition before cure. Wlien the propellant is burned the wires extend from the unburned propellants into the flame zone. They provide paths for rapid heat transfer and thus burning along the wire is faster than outside the wire. Particularly efficient are silver and copper wire, as described by Rurnbcl - for PVC plastisol propellants (Table 125). 

The rate of burning of plastic igniter cord is primarily governed by the chemical composition of the pyrotechnic and the rate of heat transfer along the support wire. 

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