Microlayer coextrusion as a route to innovative blend structures

Abstract

Nanolayer and microlayer coextrusion is a method for combining two or three polymers as hundreds or thousands of alternating layers with individual layers as thin as tens of nanometers. The possibility for utilizing microlayer coextrusion as a tool for creating microplatelets of high aspect ratio was explored. Polypropylene (PP) was combined with polyamide-66 (PA66) in microlayers. A high volume fraction of PA66 microplatelets dispersed in PP was achieved by injection molding the microlayered materials at a temperature intermediate between the melting points of the two constituents. The difference in melting temperatures provided a broad processing window of about 60°C in which the PP layers melted to form the matrix whereas the PA66 layers remained in the solid state as dispersed microplatelets of high aspect ratio. The resulting material had significantly improved oxygen barrier properties. An enhancement of 4-5 times over the barrier of the conventional melt blend resulted from increased tortuosity of the diffusion pathway.