Staged process for obsolete propellant disposal: Polymer-matrix composite waste management

In order to find a safe, permanent, and environmentally sound method for the disposal of polyurethane-based propellants, this research utilized matrix modification, ultrasound irradiation and biological technologies to develop a feasible staged process to separate the useful components from the obsolete composite propellants and to degrade or completely decompose the synthetic cross-linked polymer matrices into low molecule-weight oligomers.; In the initial stage, matrix modification was used to relax the crosslinked matrix of propellant specimen and then fragmented with centrifugal plus hydraulic forces. Most of the energetic solids were ejected and collected after this process. Subsequently an ultrasonic depolymerization with the aid of a free radical initiator was performed under the induced cavitation environment. The results indicated that the high molecule-weight polyurethane fragments had been broken down into soluble lower molecule-weight oligomers. The metallic fuel was then able to be separated from the partially degraded polyurethane binders.; Finally, the biodegradation process with fungal species capable of degrading the low polymerized polyurethane was examined and demonstrated to serve as the polishing stage to prevent the synthetic polymers in the waste stream from generating more pollution. The results indicated that the fungal degradation was able to further degrade the partially degraded polymers.; Based on the preliminary results, a staged process was proposed. The final goal is to deliver a complete operational scheme to minimize typical composite propellants wastes and other polymer matrix composite (PMC) wastes intended for landfill disposal and to reuse the separated constituents as raw materials for various applications.; Among the PMC wastes, scrape tires were selected for the same investigation because of their environmental impacts which have posed serious wastes management problems. The staged process was able to devulcanize the tire rubber by cleaving the sulfur bonds. Unlike other disposal methods, the end products through this process, the separated filler materials, have significant potential for reuse.; As the natural resources available to use is but limited and consumption of raw materials continues to grow, this staged process provide a significant and economical solution for two of the most challenging solid wastes disposal problems.