GAS AND WATER-VAPOR TRANSPORT IN A POLYKETONE TERPOLYMER

Gas and water vapour transport properties of a polyketone terpolymer ( 0.93/0.07/1 ethylene/propylene/carbon monoxide) have been investigated and related to the polymer structure. Permeability tests have been pe rformed at several temperatures (from 25 to about 65 degrees C) with f ive different gases (oxygen, nitrogen, methane, ethane and carbon diox ide), evaluating permeabilities, diffusivities and solubilities. Their dependence on temperature was interpreted on the basis of apparent ac tivation energies of permeation and diffusion (E(P) and E(D)) and of h eats of solution (Delta H-S) The investigated polymer was found to be rubbery at the test temperatures (glass transition temperature is abou t 17 degrees C), but the detected permeabilities are comparable to tho se of the glassy polymers widely used for packaging applications. Data obtained in this investigation on samples exposed to moulding tempera tures (240 degrees C) for 3 min were compared to gas permeation data ( presented in a previous paper) obtained for samples exposed at that te mperature for 33 min in order to assess possible effects on gas transp ort properties. Water vapour transport was analysed by performing both sorption (35, 34, 55 and 65 degrees C) and permeation (35 degrees C) experiments at several activities. The analysis of sorption isotherms revealed the occurrence of water clustering, which was confirmed by a reduction of water diffusivity as a function of water concentration in the polymer.