Solid-liquid adhesion energies of composite propellant components determined by solution calorimetry

The energetic or adhesive interaction between binder matrix and solid fillers as well as plasticizers and fillers is a property determining mechanical properties as strain capacity and stress at maximum or stress at break. To know such interaction energies is therefore of interest. An isoperibolic solution calorimeter is used to measure such interaction energies or heats of immersion of the solid propellant components ammonium perchlorate (AP) and aluminium (AL) with the liquid plasticizers bis-(2-ethylhexyl) adipate (DEHA) and azido-terminated oligomeric glycidylazide (GAP−A). The determined heats indicate wettability and interaction energy in units of energy per surface area of the solid component. For AP, three different grain sizes with mean diameter about 200, 90, 42 mm were used. Results indicate dependence of AP wetting on mean particle diameter: Successful wetting occurs for AP at diameters from above 90 mm. The polar interactions between the ionic AP and GAP−A greatly enhance wetting as compared to DEHA.