Abstract: The extrudate reduction phenomenon of melten polymer in the process of gas-assisted extrusion(GAE) forming was systemic studied through experiments, it is analyzed that the two main reason causing the reduction of extrudate was semi-solid melting film and melt down。The essential reason for semi-solid melting film was the relatively low temperature of gas in the extrusion die, and it could be eliminated by increasing temperature of gas or decreasing height of the gas chamber in the extrusion die. At the same time it was also point out that the semi-solid melting film to generate with the polymer its own characteristics, and indicate the viscosity more bigger, more sensitive to temperature are more easy to produce semi-solid melt film phenomenon. Furthermore, by appropriately lowering extursion temperature of melt can eliminate the phenomenon of melt down.

Key words: gas-assisted extrusion, extrudate reduction, semi-solid melting film, sagging