| 摘要 |
A method of forming a substantially uniform closed cell crystalline polymer foam article is described. The method involves: a) heating a crystalline polymer resin to a melt temperature such that the resin melts; b) selecting one or more blowing agents, at least one of the one or more blowing agents having a boiling point greater than a glass transition temperature for the resin and less than or equal to a forming temperature; c) combining the one or more blowing agents with the resin to create a mixture such that a concentration of the one or more blowing agents in the mixture is sufficient to produce a theoretical sheet foam density of less than 0.4 g/cm3 ; d) cooling the mixture to a temperature approaching a freezing temperature for the mixture; e) extruding a substantially uniform closed cell polymer foam sheet of density less than 0.4 g/cm3 from the cooled mixture; f) cooling the extruded polymer foam sheet by direct contact with a cooling surface at a surface temperature below the glass transition temperature such that the one or more blowing agents condense and the polymer foam sheet has a density of greater than 0.4 g/cm3 ; and g) forming the cooled polymer foam sheet into an article, comprising applying heat such that the condensed one or more blowing agents vaporize and the article crystallizes at a density of less than 0.4 g/cm3.
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