The Effect of Rolling Process on the Chemical Stability, Microstructure and Physical and Mechanical Properties of Double Base Solid Propellant

The chemical stability, glass transition temperature, mechanical properties, and physical structure of solid propellants are important for optimal engine performance. In this research, the effect of rolling process on these properties concerning solid propellants was investigated. Samples of double base solid propellant, prepared by the solvent method, were rolled for 2, 4, 6, and 8 minutes using a roller machine. Rolled samples were analyzed at different times using Bergman-Young tests, permeation gel chromatography, tensile test, differential scanning calorimetry, and computerized micro-scaning. The results of the Bergman-Young test showed that the propellant has optimal stability during the rolling time of about three minutes. The permeation gel chromatography test showed that with increasing the rolling time from 2 to 8 minutes, an increase in the number molecular weight and a decrease in the weight molecular weight were observed, indicating the failure of the large nitrocellulose (NC) polymer chains. The results of the computerized micro-sectioning test showed that with the increase of the rolling time from 2 to 8 minutes, the percentage of holes decreased from 10.0% to below 0.8%, and the average value of the radius of holes decreased from 40.2 to below 4.0 microns. The results of differential calorimetry test showed that by increasing the rolling time from 2 to 8 minutes, the glass transition temperature decreased from -46.08 to -48.02ºC. The results of the mechanical properties test showed that by increasing the rolling time from 2 to 8 minutes; Tensile Strength (TS) and Elongation (EL) have increased from 5.36 to 9.40 and 4.78 to 13.00%, respectively.