New condensation-type monomer combinations as ashless antiwear compositions

Abstract

Environmentally acceptable antiwear additives should preferably not contain more elements than carbon, hydrogen, oxygen, nitrogen; compounds composed of these elements can be selected or designed to be biodegradable. Most recently, lactam compounds were found to be very effective antiwear additives towards ceramic materials as well as metals. Lactam compounds are referred to as cycloamides. This paper aims at (i) describing compounds of a new antiwear additive group of lactams; particular emphasis is on caprolactam, the monomer used to synthesize Nylon 6; (ii) demonstrating the large synergistic antiwear effect observed when caprolactam is mixed with another condensation-type monomer, i.e. C 36 dimer acid/glycol monoester; and (iii) showing one example of possible practical applications of such mixtures as specific running-in lubricants. Tribological tests carried out on a high-speed/high-load pin-on-disk machine demonstrated that caprolactam is an extremely effective antiwear additive for alumina-on-alumina as well as steel-on-steel systems. Similar antiwear effectiveness was also achieved for higher molecular weight cycloamides, e.g. laurolactam. Compositions of the monoester and caprolactam were tested using the T-11 pin-on-disk tester developed by the Institute for Terotechnology in Radom, Poland. This apparatus allows one to run tests at elevated temperatures up to around 300°C. It also continuously records the coefficient of friction and linear displacement due to wear. Combinations of the monoester and caprolactam showed a striking synergistic antiwear effect and reduced friction coefficient. A new small engine running-in lubrication approach is also described. This approach not only provides excellent and most impressive running-in performance but also results in substantial economic savings in labor and materials.