Innovative polymer processing in carbon dioxide

Abstract

Carbon dioxide was used as the solvent in two innovative polymer processes, the preparation of energetic polymers and a Viton based pyrotechnic. The energetic polymer prepared was poly-3-nitratomethyl-3-methyl oxetane and the pyrotechnic was a magnesium, Teflon and Viton (MTV) crumb. Liquid carbon dioxide (LCO 2) at 140 atm and 0°C replaces methylene chloride as the solvent in the two step energetic polymers preparation. The monomer, 3,3-(methanol) methyl oxetane, was nitrated with nitrogen pentoxide (N 2O 5) and subsequently polymerized using gaseous boron trifluoride (BF 3). Polymerizations in LCO 2 simplifies solvent removal and purification. The LCO 2 solvent evaporates on release of the pressure. Supercritical carbon dioxide (SCCO 2) was used for oligomer extraction and fractionation of the polymers. To our knowledge, this was the first time carbon dioxide was used as the processing fluid for N 2O 5 nitration and for polymerization using gaseous BF 3. Various batches of MTV up to 200 grams were prepared using a new method designated the Super-Shock Process. The MTV prepared by this new process meets the requirements of a class 1.3 explosive. In this process the Viton was precipitated from an acetone/magnesium/Teflon/Viton paste with carbon dioxide, thus coating the magnesium and Teflon with Viton. Virtually no hazardous waste was generated in this process. The processing fluids, acetone and carbon dioxide were recovered and recycled. Since the starting materials were not chemically or physically altered during processing, any off specification MTV was mixed with acetone and the proper amounts of starting materials and added to the next batch. In the old process over 10 pounds of hazardous waste are produced per pound of MTV.