Dissolution of polymeric materials for recovery and recycle

The mechanism and kinetics of dissolution of various polymers were studied in organic solvents and supercritical fluids. The ability to dissolve the polymer facilitates the recovery, recycle and reuse of especially solid rocket fuels with polymeric binders. Since the binder encapsulates other components in the propellant formulation, its controlled dissolution is crucial to the recovery and recycle of all the energetic material ingredients. The principle focus of the study was the dissolution of the novel oxetane thermoplastic elastomer. The oxetane polymer was found to be highly soluble in ethyl acetate and THF but there was no evidence of dissolution in supercritical carbon dioxide. The dissolution rates of the oxetane polymer in ethyl acetate and THF were obtained and well correlated with a quasi-stationary dissolution model. Equilibrium solubility values obtained from the mathematical model on the basis of the best fit to the dissolution data were found to be in good agreement with equilibrium solubilities obtained in independent experiments. Mass transfer coefficients were also obtained from the mathematical model on the basis of the best fit. The calculated activation energies were typical for diffusion controlled dissolution. Furthermore, the dissolution of propellant simulant in various solvents was also investigated using the oxetane polymer filled with various solids including ammonium sulfate and aluminum fillers. The dissolution rates for the propellant simulant were well correlated with a pseudo-homogenous diffusion model.