Structure–Properties Relationship of a Novel Multilayer Film/Foam Material Produced through Co-extrusion and Orientation

The PP multilayer film/foams prepared by the multilayer coextrusion technique possess a unique solid/porous alternating horizontal architecture, in which the film layers can effectively suppress the premature rupture of cells in foam layers. This paper introduces a strong and lightweight layered cellular structure developed through optimized uniaxial drawing of the coextruded PP multilayer film/foams. Moreover, systematic study reveals the effects of orientation on the structure and properties of the oriented PP multilayer film/foams. Formation of subcellular interconnected porous structure decreases the bulk density with increasing draw ratio (DR) up to DR = 3.5. In addition, strain induced increase in the orientation of α crystals and crystallinity of PP during uniaxial drawing improves the tensile strength and modulus of the oriented multilayer film/foam significantly. The oriented PP multilayer film/foam with the lowest density and improved tensile properties can be obtained at DR = 4 at the optimized drawing condition.