Development of nitrocellulose based binder for ammonium perchlorate/aluminium solid propellant

Abstract

In the manufacturing of solid propellants, a binder is used to bind a mixture of oxidizer and fuel particles uniformly. In this study, nitrocellulose was developed as a binder for ammonium perchlorate/aluminum solid propellant. Since nitrocellulose is in solid state, it must be dissolved in a solvent before it can be used as a binder. An experiment to determine the suitable type and quantity of solvent was carried out from a choice of three different solvents, with each type varying in quantity too. A solvent that gave the least volume reduction was selected. To facilitate processing, which is the absorption process of oxidizer and fuel particles into the dissolved nitrocellulose uniformly, plasticizers had to be used. The plasticizers also served to decrease the volume reduction occuring during the curing process. Hence, an experiment to determine the suitable type and quantity of plasticizer was also conducted, from three different plasticizers. A ballistic evaluation rocket motor (BEM) was carried out to determine the value of thrust produced. This value was then compared with the thrust produced by a propellant with hydroxyl terminated polybutadiene (HTPB) as the binder, done by a previous researcher. These tests used standard dimensions of the rocket motor developed in UTM. Burning rate experiments were performed in a Crawford bomb under several sets of pressures to determine the value of Vieill‟s law constants a and n, which were then used to obtain the theoretical thrust value. In conclusion, ethyl acetate and castor oil were found to be the most suitable solvent and plasticizer respectively. The values obtained for the Vieill's law constants a and n were 1.7490 and 0.7467 respectively. The theoretical thrust value calculated was 188.09 N which is more than the theoretical thrust resulting from the use of HTPB as binder of 134.36 N.