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The morphology and helium-barrier properties of thermoplastic polyurethane (TPU)/ethylene-vinyl alcohol (EVOH) blends with and without dicumyl peroxide (DCP) were investigated by melting blending. A lamellar dispersion of EVOH with good helium-barrier properties was observed in the TPU matrix with DCP. The evolution of the morphology of the blends is mainly related to the variation of the viscosity ratio between the dispersed phase and the matrix phase. Compared with pure TPU, lamellar morphology increased the helium-barrier properties of the TPU/ EVOH (60/40) blend by as much as 10-fold. We also explored the effects of composition, DCP content, and blending sequence on the morphology and helium-barrier properties of the TPU/EVOH blends. The morphology of the blends ranged from a droplet-matrix to a lamellar structure. We determined the optimum amount of DCP to improve the helium barrier of the blends. The heliumbarrier properties of the blends prepared by direct blending were superior to those of the blends prepared by twosegment blending, and the blends prepared by direct blending exhibited a well-developed lamellar morphology. We compared the permeability of the samples with the theoretical results to explain the relationship between morphology and helium-barrier properties. POLYM. ENG.

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