NUCLEATION IN EDAMS AS ASSESSED BY IN-LINE ULTRASONIC MEASUREMENTS

摘要

The conditions that induce the bubble nucleation for the thermoplastic foam extrusion process in which physical foaming agents (PFA) are involved are obviously linked to the solubility parameters, i.e. temperature and pressure at a given PFA content, conditions that can be modified adding a nucleating agent. An in-line detection method based on ultrasonic sensors, sensitive to the onset of the phase separation, was used to investigate the influence of both talc and HFC-134a blowing agent concentrations on the nucleation cell density and degassing conditions for polystyrene foaming.