Development of liner for case-bonded grain with end-burning configuration

Abstract

This paper deals with the potential to manufacture case-bonded propellant grain with the end-burning configuration. The end-burning configuration is not quite suitable for case-bonded architecture due to problems related to structural integrity. One approach to address this issue is to insert a liner between thermal insulation layer and the composite propellant, which absorbs stress generated during curing process and exploitation conditions. The prepared liner is a highly elastomeric material, based on hydroxyl-terminated polybutadiene (HTPB) and castor oil (CO). The amount of curing agent, isophorone diisocyanate (IPDI), is higher to establish a covalent bonding and thus good adhesion between the liner and the propellant/thermal insulation. CO provides more anchoring sites since it has higher functionality of HTPB and, in other hand, isotropy of the liner making it more able to withstand and reduce accumulated stress within the propellant grain. The molar ratio between prepolymer (HTPB and CO) and IPDI was varied and cured material was subjected to an unaxial tensile test and examination of adhesion with propellant using a peel test.