Chemical conversions of organophosphorus compounds at elevated temperatures and the mechanism of the action of these compounds on frictional wear

Abstract

AT THE present time it must be considered as established that additives reducing frictional wear under high-load conditions--above all, organic compounds of phosphorus, sulphur, and chlorine--react chemically with metallic surfaces in contact and modify them in an appropriate manner [1]. Due to friction, relatively high temperatures develop in the most highly stressed regions of contact of the metallic surfaces causing the additives to undergo a series of chemical changes and the reactive substances thereby formed interact chemically with the metal. Consequently, to elucidate the mechanism of the action of additives, it is extremely important to establish how they change at high temperatures. Within this scheme, the results given below of a s tudy of the thermal conversions of additives consisting of various organophosphorus compounds must be considered. The thermal conversions have been studied of a series of organophosphorus compounds representative of typical additives reducing frictional wear under high-load conditions, namely: trialkyl phosphites, trialkyl phosphorotrithioites, metal dialkyl phosphates, and metal dialkyl phosphorodithioates. The experiments were performed in a special apparatus consisting of a reactor in which the decomposition of the organophosphorus compounds was carried out and a system of absorbers for the quantitative determination of the gaseous (hydrogen sulphide, phosphine) and highly volatile (low-molecularweight unsaturated hydrocarbons) decomposition products. The decomposition was carried out in an atmosphere of nitrogen. Trialkyl phosphites. As has been shown previously [1], at elevated temperatures trialkyl phosphites--tributyl phosphite and trioctadecyl phosphi te--undergo the following conversions;