In Situ Visualization for Control of Nano-Fibrillation Based on Spunbond Processing Using a Polypropylene/Polyethylene Terephthalate System

Abstract In situ generation of polyethylene terephthalate (PET) nanofibrils in polypropylene (PP) microfibers via fiber spinning in a spunbond process was studied in this work. The effects of polymer flow rate and air speed in the drafter on the formation of PET fibrils were investigated using a pilot scale machine. An in-situ visualization technique was applied to examine the fiber evolution events and stretch profile at die exit. A scanning electron microscope was used to analyze and investigate the morphology of the dispersed domain. The PET dispersed phase was fibrillated within the PP matrix such that a nonofibrillated composite containing fibrils with an average size around 100 nm was obtained. It was found that the final fibril size directly depends on the degree of die swell, the air speed and the polymer flow rate. It was also found that the in situ observed size of the micro-scale PP/PET fibers was well correlated to the size of the nano-scale PET fibers formed in the PP matrix. The visualization results revealed that a smaller fibril diameter was obtainable by increasing the stretching on the spin line and/or decreasing the die swell.