Oxygen barrier, free volume, and blending properties of polyamide 12/poly (vinyl alcohol) blends

Abstract

Oxygen permeation rates, average volumes of free‐volume‐cavities (Vf), and fractional free volumes (Fv) of polyamide 12 (PA12)/poly(vinyl alcohol) (PVA) (ie, PA12xPVA05y, PA12xPVA08y, and PA12xPVA14y) blend films with varying PVA degrees of polymerization reduced to a minimum value when their PVA contents reached a corresponding optimal value, respectively. The minimum oxygen permeation rates, Vf, and Fv values obtained for the optimal PA12xPVAzy blown films were reduced considerably with decreasing PVA degrees of polymerization. Experimental findings from dynamic mechanical analysis, differential scanning calorimetry, wide angle X‐ray diffraction, and Fourier transform infrared spectroscopy of the PA12xPVAzy blend series suggest that PA12 and PVA in PA12xPVAzy are miscible to some extent at the molecular level when their PVA contents are near and less than the corresponding critical values. The considerably enhanced oxygen barrier properties of the PA12xPVAzy blend films with optimized compositions are attributed to the significantly reduced local free volume characteristics.