Stress Related Surface Tension Effects in Hard Elastic Polymers.

Stress depressions of hard elastic polypropylene, hard elastic high impact polystyrene, and Gore-Tex, A nonelastic, porous, Teflon material were measured when these polymers, under load, were subjected to changes in their environment from air to various nonswelling liquids. The stress depressions were studied as a function of liquid surface tension and viscosity and the strain imposed on the materials. Results indicate that these microfibrillated polymers contain a substantial surface energy component in their stress which is independent of strain at high tension. This surface energy component is apparently inversely proportional to the average microfibril diameter. It suggested that a maximum fibril diameter limiter exists such that, above this limit, hard elastic behavior will not occur. Author