Triazol polymer, first step for a self-healing PBX

Abstract. Triazol polymer, first step for a self-healing PBX Self-healing is a technique used to fix physical defects in polymers caused by various aggressions (mechanical, chemical). In the field of energetic materials, cracks induced by stress on a polymer-bonded explosive (PBX) can represent a risk, making it essential to mitigate this hazard. The self-healing solution appears to be an ideal approach due to its ease of implementation. The solution is based on the introduction of capsules which enable self-healing phenomenon through a chemical reaction with the polymer matrix when a crack appears. This innovation will help to reduce the reject rate due to nonconformity related to crack and will decrease the risk of accidents in operation. Encapsulation The technique of encapsulation consists of encapsulating a reactive healing function of the polymer. The capsule is then added in the composition, during the process. After a crack, the capsule breaks and releases the healing matrix which will be able to react with the cast PBX formulation to fix the crack. For this purpose, the healing matrix is made up of chemical functions that complement and can react with the reactive functions of the cast PBX formulation. The mechanism selected here is based on the Huisgen reaction, leading to the formation of a triazole, resulting from the reaction between an azid group and an alkyne function. Self healing principle demonstration As self healing phenomenon thanks to Huisgen reaction is based on the reactivity of the azide group with alkyne functions, alkyne multifunctional platforms have been developed. To react with alkyne groups of the multifunctional platform, Azide polymers has been synthetized. The demonstration of the feasibility of the Huisgen reaction between the azide polymer and an alkyne functionalised platform has been successfully completed and characterised. Lastly, the encapsulation of the alkyne platform has been studied and performed thanks to a microencapsulation process under solvent. With the realization of the azide functionalized cast PBX with encapsulated alkyne platform, the full concept could be validated after a voluntary stress has been applied to release the alkyne functions and thus enable the self healing of the polymer.