New condensation-type monomer combinations as ashless antiwear compositions

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 rec ently, 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 ant iwear additive group of lactams; particular emphasis is on caprolactam the monomer used to synthesize Nylon 6; (ii) demonstrating the large synergisti c antiwear effect observed when caprolactam is mixed with another condensat ion-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 eff ective antiwear additive for alumina-on-alumina as well as steel-on-steel s ystems. Similar antiwear effectiveness was also achieved for higher molecul ar weight cycloamides, e.g. laurolactam. Compositions of the monoester and caprolactam were tested using the T-ll 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 degreesC. It also cont inuously records the coefficient of friction and linear displacement due to wear. Combinations of the monoester and caprolactam showed a striking syne rgistic antiwear effect and reduced friction coefficient. A new small engin e running-in lubrication approach is also described. This approach not only provides excellent and most impressive running-in performance but also res ults in substantial economic savings in labor and materials. (C) 2001 Elsev ier Science B.V. All rights reserved.