Abstract
Blends of polyethersulphone (PES) and a thermotropic copolyester based on hydroxynaphthoic acid and hydroxybenzoic acid residues have been examined. The permeability to oxygen of thin pressed films of a range of compositions has been studied. It is found that fairly modest additions of the liquid crystalline polymer (LCP) lead to a pronounced improvement in barer properties. This improvement is ascribed to the formation of a thin surface layer of the LCP. The existence of this LCP surface layer is supported by examination in the scanning electron microscope of dimethyl formamide etched samples: etching does not remove all the PES because it is protected from the etchant by the surface layer.
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