A molecular-scale view on rotary lip sealing phenomena

Abstract Rotary lip sealing is not described sufficiently by present modelling techniques. Characterizing the sealed fluid only as a viscous continuum has not yet led to a conclusive description of the well known sealing, lubricating and pumping phenomena. This paper presents a new hypothesis and offers a new and different view on rotary lip sealing assuming significant molecular interactions within the sealed fluid to have an important role which are expected to cause a non Newtonian flow behaviour. Experiments with two test fluids consisting of different molecular composition are carried out. Differences in the operating behaviour are pointed out and explained by considering viscous and non Newtonian effects i.e. the molecular composition. The influence of the shaft surface upon operating conditions will be shown and the mode of friction in the contact zone of rotary lip seals will be determined.