| 摘要 |
Method of reducing the density of an essentially closed cell thermoplastic resin foam material by secondary expansion thereof. The method consists in increasing the gas pressure inside the cells, maintaining the increased cell pressure for an extended length of time and thereafter heating the foam material to a temperature in excess of its hot plastification temperature in order to bring about secondary expansion thereof. In one example the low-density polyethylene material was expanded to produce a foam having a density of approximately 0.085 g per cm<3>. This foam was then pressurized with nitrogen and subsequently underwent secondary expansion to produce a foam with a density of approximately 0.036 g per cm <3>.
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