Accession Number:

ADA063596

Title:

On the Mechanism of Pressure-Induced Environmental Stress Cracking in Polystyrene.

Descriptive Note:

Technical rept.,

Corporate Author:

CASE WESTERN RESERVE UNIV CLEVELAND OHIO DEPT OF MACROMOLECULAR SCIENCE

Personal Author(s):

Report Date:

1978-12-22

Pagination or Media Count:

41.0

Abstract:

Fluids conventionally classified as inert exerted a strong stress crazing and cracking effect on certain amorphous polymers when they are deformed in tension under pressure. Fourier transform infrared difference spectroscopy has been utilized to measure the concentration of trace amounts of fluid penetrating the polymer during deformation. Measurable fluid penetration was found to take place only in dilated structures as large as crazes. The penetration level depended upon craze density and structure, viscosity or the fluid and the time or rate of the experiment. A atmospheric pressure, the penetrating fluid front lagged behind the dry growing craze tip. Radial concentration distributions were successfully described by a semiquantitative porous transport model which yielded a specific penetration coefficient. This coefficient was a strong function of the hydrostatic pressure and the viscosity of the penetrating fluid. It is suggested that the hydrostatic pressure decreases the void content in the polymeric solid, yet due to the pressure gradient concurrently enhances the dynamics of fluid transport. At a critical pressure, the polymer undergoes the brittle-to-ductile transition. Here irreversible deformation by shear is preferred over the void forming craze or cracking mechanism. Author

Subject Categories:

  • Plastics
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE