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

Abstract

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.

Research on improved gas‐assisted extrusion of plastic sheets based on time–temperature equivalence principle

“…Using GAE [23,24] during conventional sheet extrusion, the stress on the melt in the gas-free channel section can be released to a certain extent through the gas-assisted channel section, thus relieving or eliminating the adverse extrudate swelling. The stress released from the melt in the die is related to the length of the gas-assisted channel section and the extrusion speed of the extruder.…”

Tensile modulus of clay‐reinforced system supposing the interphase effectiveness for load transferring

“…Nanoclay consists of firmly packed layers, with thickness of 1 nm and length of few microns. [1][2][3][4][5][6] The clay layers are exfoliated or inflamed (intercalated) in the matrix. [7][8][9][10] Generally, the extent of intercalation/exfoliation depends on the capabilities of polymer chains and clay to interact via interfacial zone.…”