Thermo-mechanical properties of β-nucleated polypropylene multilayers

With the aid of a layer-multiplying coextrusion technique, polymer composites comprising up to 128 uniform alternating layers of polypropylene random copolymer (PPR) and beta-nucleated PPR were produced. Crystallization, melting behavior and mechanical properties (bending, tensile and impact characteristics) were investigated. The results not only show an increasing amount of beta-crystals, but also improved mechanical properties. In particular, the temperature dependence of the bending modulus reveals that a high number of layers leads to an increase in stiffness across a wide range of temperatures. For each layer composition, a distinct temperature can be determined that marks the upper limit of this synergistic effect. (C) 2014 Elsevier Ltd. All rights reserved.