Multilayer Coextruded Polyolefin Films Improve Processability and Reduce Flammability

Via multilayer coextrusion we have fabricated films consisting of 100s of layers of polypropylene (PP) and polyethylene (PE). Although neither polymer shows strain hardening during extension the multilayers have extensional viscosities significantly greater than what is predicted with a simple 2-component volume average model. This behavior is predicted with a 3-component model that accounts for the many PE/PP interfaces using only interfacial tension as a model fitting parameter ( A.M. Jordan et al. J. Rheol. 2019). The extracted interfacial tension from transient elongational viscosity measurements agrees with the interfacial tension extracted from fitting small amplitude oscillatory shear data with the Palierne model. These multilayer PP/PE films opened the temperature and time operating window for thermoforming and reduced dripping during burning.