In-situ visualization of polypropylene crystallization during extrusion

Crystallization is a critical phenomenon that governs the morphology and the properties of a semi-crystalline polymer. In this study, a visualization chamber with two flush-mounted sapphire windows was designed and installed before the die exit to investigate polypropylene crystallization during a tandem extrusion process. Through in-situ visualization of crystallization, we verified for the first time that crystallization can be induced in continuous extrusion by controlling the temperature of the second extruder after complete melting of the material in the first extruder. It was visualized that the crystals formed in the melt and they moved with the flow during the process.