THE NATURE OF DEFORMATION OF THE SURFACE LAYERS OF POLYMETHYLMETHACRYLATE UNDER FRICTION,
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OHIO
Pagination or Media Count:
The nature of deformation in surface layers of thermoplastic amorphous plastics during friction was studied. Friction was cuased by sliding a spherical steel indentor over polymethylmetacrylate at various velocities. At low velocities, elastic and forced-elastic deformations occur in the surface layers and there is roughening of the plastic. The deformed surface layers regain their shape at temperatures corresponding to the highly elastic state. With increased sliding velocity, the forced-elastic deformation is localized in a finer layer. Beginning at some velocity, depending on the temperature and activation energy of the shift in polymer chain segments from one equilibrium position to another, a transition to a purely elastic deformation of the surface layers and roughening of the plastic occurs. Drastic destruction of the surface layer takes place in elastic deformation at pressures above a specified value. Photographs of the effects produced on the plastic are given, some of them made with polarized light.