| 摘要 |
The present invention provides microcellular articles, as well as methods and apparatuses for producing polymeric foams, and, in particular microcellular material. The methods involve forming a gas blanket within a polymer processing die that prevents contact between the polymer melt and surfaces of the die during extrusion. In one set of embodiments, the gas blanket is provided by gas diffusing out of surfaces of the nucleated polymer material. In other embodiments, the gas blanket is formed by introducing a gas from an external source into the polymer flow channel within the die. The dies, according to the invention, are specially configured to generate and to support the gas blanket. The extruded foams are free of surface defects that, typically, arise from contact between the polymer melt and the die surfaces.
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