In situ formation of poly(ethylene naphthalate) microfibrils in polyethylene and polypropylene during extrusion

Tensile properties, morphology and the relationship of microfibrils to the extrusion die diameter for poly(ethylene naphthalate) (PEN)/polyethylene (PE) and PEN/polypropylene (PP) blends were investigated. Scanning electron micrographs of the blends revealed that the fibril morphology was developed during extrusion through the die. “Skin-core” morphology was observed and the morphology (size and form for the dispersed phase) was in turn influential on the tensile properties. After drawing followed by annealing of the fibrillized blends, up to 100% increase in the tensile modulus was observed and the tensile strength was increased by up to one order of magnitude. Polarized Raman spectroscopy was used to follow the change in orientation of the blend components during microfibrillization.