| 摘要 |
1278364 Tetrafluoroethylene polymer films &c W L GORE & ASSOCIATES Inc 30 April 1970 [3 Oct 1969] 20739/70 Heading B5B [Also in Divisions C3 and F2] A shaped article of an unsintered tetrafluoroethylene polymer which is uniaxially expanded and oriented, has a fibrillow structure and has a specific gravity of less than 1À4 may be produced by increasing, through controlled stretching, the length of the article without a compensating decrease in the other dimensions of the article. The controlled stretching may be achieved by drawing off polymer tape from a drum at a higher speed than it is supplied by the drum. Suitable polymers are polytetrafluoroethylene and tetrafluoroethylene/hexafluoropropylene copolymer. Ethylene or chlorotrifluoroethylene may be present as comonomers. The shaped article may be in the form of a ribbon, rod or pellicle. The stretching may include a heat-setting step comprising applying heat to the stretched article while it is constrained from retraction thereby relieving stress within the stretched article.
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