Tribochemical interactions between molybdenum dithiophosphate and succinimide additives

Tribochemical interactions between antiwear/antifriction molybdenum dithiop hosphate (Modtp) and dispersant amine additives (polyisobutenyl succinimide (PIBSI) and polyisobutenylactetylamine (PIB-Amine)) have been investigated by a coupling friction experiment in a Cameron Flint tribometer and chemic al analysis by transmission electron microscopy (TEM), XPS and AES, Antagon ist effects have been observed on friction data in the case of the Modtp/PI B-Amine combination in oil. in contrast, friction properties of the Modtp h ave not been modified in a significant way by adding PIBSI, Both XPS and AE S suggest that the addition of PIB-Amine to Modtp has inhibited the formati on of the tribofilm, whereas in the case of the addition of PIBSI to Modtp no noticeable change in the film composition was observed. Observation by T EM of wear fragments confirms an inhibition of the formation of the polypho sphate/MoS2 tribofilm when PIB-Amine is used as a detergent-dispersant addi tive. All the results suggested that the amine plays a fundamental role in inhibi ting the Modtp tribofilm formation. The results with PIBSI allow us to conc lude that the role of the amine depends either on its ability to form coord ination complexes with Mo or on its adsorption properties on metallic surfa ces. Copyright (C) 2000 John Wiley & Sons, Ltd.