AbstractSeven semiflexible unsaturated polyester resins based on isophthalic acid, maleic anhydride and polyethylene glycol‐200 and propylene glycol (in different proportions) have been synthesised and characterised for gel time, exotherm peak temperature, tensile strength, percentage elongation, bond strength, nitroglycerine absorption, water absorption, flame resistance and voltile losses. The effect of glycol variation on these properties has also been discussed. Based on the data for various characteristics, resin 4 has been selected for inhibition and static evaluation of propellant. The propellant sustainers containing 2 NDPA have been inhibited with resin 4 without the application of any barrier coats and statically fired at ambient, cold and hot temperatures. The results of the static firings prove the worthiness of the new direct bonding inhibition syste