THE BEHAVIOR OF POLYMER-SOLUTIONS IN CONCENTRATED CONTACTS - IMMOBILESURFACE-LAYER FORMATION

The film-forming properties of solutions of low-to-medium molecular we ight polyisoprenes in synthetic hydrocarbon have been studied using th in film interferometry. It has been shown that the lubricating films f ormed in rolling, concentrated contacts have two components. At very s low speeds, the polymer forms an immobile film of thickness equivalent to two radii of gyration of the polymer molecules. This film thicknes s is independent of speed but is gradually squeezed from the contact w hen motion is halted. The film is likely to represent two monolayers o f polymer, one on each surface, and can be regarded as a boundary lubr icating film. As the rolling speed is raised, a conventional elastohyd rodynamic film is formed which is superimposed on the immobile film. T he immobile films formed are similar to those detected using a force b alance apparatus and reported elsewhere in the literature.