Subcritical gas-assisted processing of ethylene vinyl alcohol + nanoclay composites

Ethylene vinyl alcohol (EVOH) was melt compounded with an organomodified nanoclay (NC) at a loading level of 5% by weight in a twin-screw extruder using a subcritical gas-assisted process (SGAP). Carbon dioxide and nitrogen were used as blowing agents to induce foaming inside of the barrel of the extruder and as the melt exits the die. Samples processed with SGAP demonstrated better dispersion of NC vs the traditional extrusion process due to the additional stresses that bubble expansion provides during foaming. The dispersion was assessed by dynamic rheology, wide-angle X-ray diffraction, scanning electron microscopy, and microcomputed tomography. Additionally, it was found that the inert gasses used in SGAP prevented some of the thermo-oxidative degradation EVOH experienced during processing, as evidenced by thermogravimetric analysis and Fourier transform infrared spectroscopy.