A Novel Approach to Predict the Cured Mechanical Properties of HTPB-Based Composite Solid Propellant

R value (~NCO/~OH ratio) is generally used as a guideline to fix up the propellant formulation. Given the batch to batch variation in the raw materials, formulation fixed based on estimated R value, quite often, yields cured propellant having undesirable mechanical properties. This, in turn, warrants several trials, leading to time delay and wastage. This gave impetus for the authors to take up this study. Authors mixed binder, curing agent, cross-linker and chain extender only such that the R value is kept within the desirable range (0.7–0.8). Thus, six formulations were made with R values ranging from 0.7 to 0.8 and were cast and cured at 50 °C and 20 °C. The cured specimens, named as Gumstock, were evaluated. For a particular R value, the properties of Gumstock were compared with those of 20 and 700 kg level batches of propellant produced using the same lots of binder, curing agent, cross-linker and chain extender along with other ingredients while keeping the same R value. The findings of the authors with respect to Gumstock level properties are in line with that reported for the cured propellant in the literature. This study, made it possible to assess the cured networks formed at different R values in terms of thermal analytical techniques viz. DSC and TGA. Based on the study, authors endeavoured to develop correlation between Gumstock and propellant level properties, to overcome the uncertainties because of subtle batch to batch changes/variation in raw materials.