Study On Theory And Equipment For Extrusion Microcellular Foaming Formation

Microcellular foams (MCF), typically defined as foamed plastics with a cell size between 0.1-10 μm and a cell density between 10⁹-10¹⁵cells/cm³, have aroused tremendous research interest because of their unique properties and outstanding performance. Supercritical Carbon dioxide(SC-CO₂), as a possible replacement of traditional physical foaming agents, have high diffusivity in polymer melts and can get high nucleation rate. In this research, SC-CO₂ was added to a twin-screw extruder as physical foaming agent to get polymer/gas solution. Micro-cell nucleation has been successfully promoted using a gear pump where thermodynamic instability is induced by a rapid pressure drop in this flowing polymer/gas solution. The article based on the molecules thermo motion and dynamics, the process of nucleation and cell growth was . illustrated in detail from both macroscopically thermo-chemistry and microcosmic molecules dynamics. The competition theory and mechanism was analyzed to supply the extrusion foaming formation. The author designed and made up a technical processing chart, operation parameter control and experimental setup. The effects of the screw elements, screw rotation rate, gas amount and the temperature of the melt and the die on the foam configuration were thoroughly studied.