Three kinds of polypropylene (PP) with different viscosities were blended with poly(vinyl alcohol) (EVOH) to prepare 90/10 PP/EVOH blends

and the blends were then molded into hollow parts via water-assisted injection molding (WAIM). Samples were cut from locations near the gate (marked as 1#) and the end of flow channel (marked as 2#) of the WAIM blend parts

and the phase morphologies at three regions across the residual wall of the samples were observed with scanning electron microscope. The toluene permeabilities of the samples cut from the WAIM blend parts were measured. The phase morphologies at the three regions in the samples were interpreted with the aid of flow fields within the mold cavity under high-pressure water penetration during WAIM. Coarse fibers appeared in both outer and inner layers and droplets in the core layer for the sample taken from location 2# of the WAIM blend with high viscosity ratio

which resulted in modestly improved barrier performance of the sample compared with the WAIM corresponding PP sample (about 2.4 times). Slim fibers existed in the outer and inner layers and coarse and long fibers in the core layer for the samples taken from location 2# of the WAIM blends with low viscosity ratios

which resulted in greatly improved barrier performance of the samples compared with the WAIM correponding PP sample (about 9.8 times for the blend with the lowest viscosity ratio). Average diameters of dispersed fibers for the samples taken from location 1# of three WAIM parts were larger than those taken from location 2#

which resulted in lower barrier performance for the former samples.