Effect of External Stress on the Transport of Fluids in Thermoplastic ResinSystems

摘要

The transport properties of liquid penetrants into the thermoplastic resin, poly-aryl-ether-ether-ketone were investigated. The primary objective of this work was to study the effect of external applied stress on the diffusion and solubility/swelling of fluids with PEEK. The solubility and rate of penetration, i.e., diffusion, into the resin system are greatly increased by the application of stress: we call this phenomenon SEDS (stress enhanced diffusion and solubility/swelling). All eight fluids studied, benzene, toluene, methylene chloride, chloroform, carbon disulfide, methanol, acetone, and even water exhibit SEDS. The effect is particularly striking for crystalline PEEK where the solubility is markedly increased and the time to reach saturation, i.e., the induction period is reduced when the applied stress exceeds a critical value. For example, at 22'C the solubility of toluene into 29% crystalline PEEK increases from 9 wt% to almost 40 wt% upon the application of a tensile stress of 35 MPa. Furthermore, the time for 0.25 mm thick crystalline PEEK film to reach its saturation value was reduced from 1000's of hours to less than 10 hours.