Influence of Guanylurea Dinitramide (GUDN) on the Thermal Behaviour, Sensitivity and Ballistic Properties of the B-KNO3-PEC Ignition System

Boron and potassium nitrate are the key components for the ignition system of the igniter composition for rocket propellants. Boron-potassium nitrate-ethyl cellulose (B:KNO3:PEC) in proportions of 30:70:10 is a well established igniter composition. The composition delivers a maximum pressure in the range 4.0-4.6 MPa in closed vessel firing at a loading density of 0.01 g/cm3. For the effective ignition of a large booster stage propellant (length more than 4 m), an enhancement in the maximum pressure, without affecting safety, is a prime requirement. The use of guanylurea dinitramide (GUDN) in an igniter composition has not been reported in the literature. Hence, the present study on the effect of GUDN on the combustion behaviour and sensitivity of the B/KNO3 composition (30/70) has been carried out. Several compositions containing different weight percents of GUDN were prepared. Their thermal behaviour was determined by thermal analysis DSC-TGA. Their sensitivities to external stimuli such as impact, friction and spark were evaluated. The results of closed vessel firings indicated that GUDN-based igniter compositions produced higher peak pressures (up to 4.5 MPa to 5.8 MPa), with invariably lower burning times, compared to the control composition. The REAL computer programme indicated an increase in the flame temperature of the composition from 2238 K to 2425 K on addition of GUDN. All of the compositions were insensitive towards friction up to 36 kg, and towards spark up to 5 J energy.