Molecular weight dependence of some rheological and thermal properties of perfluoropolyethers

✍ Scribed by G. Marchionni; G. Ajroldi; G. Pezzin

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 443 KB
• Volume: 24
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(88)90114-0

✦ Synopsis

The glass transition temperatures and the viscosities (over a very large temperature range) have been measured as a function of molecular weight, for two different series of perfluoropolyethers. The results have been interpreted according to well-known free-volume models. The Williams--Landel and Ferry equation describes the viscosity data with values offs_(the fractional free volume at Ts) close to 0.04 and with values of "r (the free-volume expansion coetlicient) close to 7 × 10-4°C -~. The critical molecular weight, Me, is approximately 5000-6000 for perfluoropolyethers from hexafluoropropene and 7800 for perfluoropolyethers from tetrafluoroethene.