Transport properties of thermoplastic/thermoset blends

Gas transport properties are reported for two series of films prepared from initially miscible thermoplastic/thermoset blends, respectively, polystyre ne PS/thermoset and poly(2,6 dimethyl 1,4 phenylene oxide) PPE/thermoset bl ends. The thermoplastic contents are such that in both cases, after the pha se separation, the continuous phase is the thermoplastic-rich phase and sca nning electron microscopic photomicrographs clearly evidenced the dispersio n of thermoset-rich nodules in the continuous thermoplastic-rich phase with a more tortuous morphology in the case of PPE based films. Permeability me asurements were made for O-2 and CO2 at 20 degrees C and a reduction in per meability coefficients was observed with increased thermoset content. Analy sis using Maxwell law suggests that for all thermoplastic/thermoset blends, the thermoset particles can be considered as impermeable to gas and that t he diffusion takes place in the continuous phase. Ln the case of PPE based films, the higher decrease of permeability than that predicted by the law h as been related to the morphology of the blends and thus the tortuosity and to a partial miscibility of the thermoset in the thermoplastic. (C) 1999 J ohn Wiley & Sons, Inc.