Brief Review on Glycidyl Azide Polymer (GAP) Curing Mechanisms by Isocyanate and Isocyanate-Free Curing Agents

Glycidyl azide polymer (GAP) is one of the most active energetic binders used in highenergy composite solid propellants in the future. An energetic insensitive polymericbinder is one of the most important ingredients in energetic composite propellantsformulations. The polymeric binders used in composite solid propellants are usually crosslinked polyurethane elastomers that provide a binding matrix for solids such as oxidizers andmetal fuels with a plasticizer and other additives in small amounts. The energetic propertiesof the binder are due to the azido groups that decompos under combustion conditions andconvert to nitrogen gas. In the present paper, the GAP curing mechanism with isocyanateand isocyanate-free curing agents have been investigated. Studies show that cured samplescuring with isocyanate and isocyanate-free curing agents have good tensile strength andelongation but the curing time varies depending on the type of curing agent used. CuredGAP with isocyanate curing agent during storage shows cracking propagation, while GAPsample cured with isocyanate-free curing agent (BPS) yields better curing without anycavities and bubbles during storage.