Effect of Coextrusion On Pp/Ldpe Bicomponent Blown Films: Raman Spectroscopy for Real-Time Microstructural Measurements

The effect of coextrusion on the microstructure of polypropylene (PP) and low-density polyethylene (LDPE) bilayer films was investigated by the use of Raman spectroscopy. The onset crystallization-time difference for PP versus LDPE components is an important parameter that controls the orientation and morphology of the coextruded films. Although the overall molecular orientation of PP and LDPE was not significantly different in multilayer films, single-layer LDPE films displayed some row-nucleation of crystals that was not observed in the LDPE layer in coextruded films. Also, there was a slight decrease of crystalline a-axis orientation for coextruded LDPE layer relative to that obtained for single-layer LDPE films.