A novel barrier material consisting of alternating layers of pure polypropylene (PP) and polypropylene conventionally blended with ethylene-vinyl alcohol copolymer (EVOH) was prepared by microlayer coextrusion.The morphology structure of(PP+EVOH)/PP microlayered composites and its effect on gasbarrier properties

mechanical properties and crystallization behavior were characterized by SEM

DSC

gas-permeability and tensile tests.The results suggested that

through microlayer coextrusion

PP layers and (PP+EVOH) layers were combined as an alternatingly multilayered structure along the extrusion direction.The morphology of EVOH phase in PP matrix was changed from zero-dimensional sphere to one-dimensional fiber

then to twodimensional sheet with the increase of layer number

which caused significant improving of gas-barrier properties and enlongation at break of (PP+EVOH)/PP microlayered composites compared with (PP+EVOH) conventional blends.The crystallization behavior of microlayered composites was also influenced obviously by their structure and morphology.In addition to the PP phase in (PP+EVOH) layer

PP layer was also affected by the heterogeneous nucleation of EVOH due to the thin PP layer and the increase of interface when the layer number exceeded 64 layers.