Abstract

Development of a new method for quantitative estimation of liquid ingredients used in composite propellant using refractometry technique

Author(s): Mehilal, K.I.Dhabbe, V.S.Wani, K.K.Radhakrishnan, B.Bhattacharya

Composite propellants are themost important class of solid rocket propellants and basically contain ammoniumperchlorate as an oxidizer, aluminium powder as a fuel and hydroxy terminated polybutadiene as a binder. It also contains certain process aids such as dioctyl adipate as plasticizing agent and a mixture of n-butyl alcohol and trimethylol propane as an adduct to achieve desired elongation and tensile strength, respectively, after curing with bi-functional isocyanates. The solid ingredients are dispersed in a binder matrix, which is also referred as ‘PrepolymerÂÂ’ a terniarymixture of HTPB, DOA and adduct which is responsible for processibility of the composition and mechanical strength of the cured propellant grains. A systematic study has been carried out to quantify the exact percentage of liquid ingredients used in prepolymer before addition of solid ingredients using refractometry technique at different ratio and temperatures. The data obtained by analyzing refractive indices of individual ingredients as well as their mixture at different ratio and temperatures reveal that on comparing with standard refractive index of liquid ingredients and prepolymer to that of unknownmixture of prepolymer at a given temperature, the percentage of liquid ingredients can be quantified successfully even if there is a change in refractive index at fourth place.