| http://www.w3.org/ns/prov#value | - U.S. Pat. Nos. 4,640,933, 4,633,361 and 4,694,027 disclose methods for the preparation of expandable polyolefin compositions using isobutane; or a mixture of isobutane and chlorofluorocarbons and fluorocarbons as the blowing agent; or a mixture of at least 70% isobutane and other hydrocarbons as the blowing agent and a fatty acid amide as a stability control agent.
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