High-Temperature Stabilization of Polyphenyl Ethers By Inorganic Salts

The free radical-induced high-temperature (to ca 370 C) oxidative degradation of polyphenyl ethers is shown to be drastically curtailed by the oxides, hydroxides and carbonates (but not the neutral salts) of the alkali metals and barium. The inhibiting entities form colloidal or molecularly soluble complexes with the ether, and function in very low concentrations. Mechanisms are proposed which invoke either the basicity of the effective salts, or their ability to destroy peroxy radicals via superoxide formation. Properly designed inhibitors of the types discussed are of interest in polyphenyl ether-based lubricants for very-high-output aircraft turbine engines. Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Pittsburgh, Pennsylvania, October 5–7, 1971