GAS-TRANSPORT PROPERTIES OF ETHYLENE PROPYLENE/CARBON MONOXIDE POLYKETONE TERPOLYMER/

The demand for heat-stable and easily processable polymeric materials with good gas-barrier properties is becoming more and more important d ue to the advent of new technological applications in the field of foo d packaging. A renewed interest has arisen for a polyketone class of p olymers, which seems to fulfill these requirements. Our attention has been focused on a polyketone terpolymer (0.93 : 0.07 : 1 ethylene/prop ylene/carbon monoxide) in order to determine the transport properties and to relate them to the polymer structure. Permeability tests have b een performed at three different temperatures (25, 35, and 45 degrees C) with three different gases (helium, oxygen, and carbon dioxide). Pe rmeabilities, diffusivities, and solubilities have been evaluated. The ir dependence on temperature was interpreted on the basis of permeatio n and diffusion apparent activation energies (E(p) and E(d)) and of he ats of solution (Delta H-s). The investigated polymer has been found t o be rubbery at the test temperature (glass transition temperature is about 17 degrees C), but the detected permeabilities are comparable to those of glassy polymers widely used for packaging applications. The experimentally determined diffusion coefficients have been related to the semicrystalline nature of the polymer and to the different dimensi ons of the gas adopted in the investigation. The gas-solubility coeffi cients determined from permeability measurements were related to the f orce constant of the gas molecules in the Lennard-Jones (6-12) potenti al field equation. (C) 1993 John Wiley & Sons, Inc.