Synthesis of an alkynyl neutral polymer-bonding agent and its enhancing effect on tensile strength of glycidyl azide polymer-based propellants

A novel alkynyl neutral polymer-bonding agent (NPBA) was synthesized by a three-step approach. The molecular structure and thermal characteristics of alkynyl NPBA were analyzed. To reveal the influence of alkynyl NPBA on the mechanical properties of glycidyl azide polymer (GAP)-based propellants, two types of GAP propellants with Desmodur N-100 and alkynyl-terminated polyethylene glycol (APE) as curing agents were prepared and mechanical properties of the propellants were fully investigated. Tensile strength and initial modulus of propellants were notably promoted with the increase in alkynyl groups content of alkynyl NPBA with Desmodur N-100 as curing agent. The interfacial adhesion property between GAP binders and CL-20 fillers was greatly improved by alkynyl NPBA, and dewetting phenomenon of propellants during uniaxial tension was markedly attenuated. The wettability of GAP binders and solid fillers was good and the enhancing effect of alkynyl NPBA on tensile strength of GAP propellants was notable. Tensile strength and initial modulus of propellants were notably increased and their maximum elongation was decreased with the increase of alkynyl group content of alkynyl NPBA in propellants when APE was used as a curing agent. In addition, the dynamic mechanical analysis results showed that internal friction resistance of GAP molecular segment motion of GAP propellants was increased and interactions between GAP binder and solid fillers became much stronger with alkynyl NPBA. A notable enhancement effect on tensile strength and initial modulus of GAP propellants was demonstrated with alkynyl NPBA as bonding agent.