Crosslinking of tetrafluoro-ethylene-perfluoro-(methyl vinyl ether) perfluoro-elastomers with electron beam irradiation

✍ Scribed by Logothetis, Anestis L

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 60 KB
• Volume: 48
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199910)48:10<993::aid-pi259>3.0.co;2-#

✦ Synopsis

Pre-shaped per¯uoro-elastomeric articles were crosslinked by electron-beam irradiation. Doses of 10±15 Mrad are adequate to give a gel content of more than 95%. Irradiation experiments were carried out on the pure polymer free of ®llers, processing aids or curing chemicals. The physical properties of `O'-rings thus crosslinked are comparable to those chemically crosslinked. Addition of free radical traps, such as triallyl isocyanurate, accelerates the crosslinking process and improves the physical properties. Irradiation in addition to crosslinking also causes chain scissions. The per¯uoroether group appears to be the focus of the radiation attack. Radical intermediates and ions, produced by the ionization and excitation steps, undergo chemical reactions which cause changes in the molecular structure of the polymers. These changes are (a) formation of small molecules such as CF 4 , COF 2 , CF 3 OCF 3 and CO 2 via side chain scission, (b) main chain scission of the polymeric chains, and (c) crosslinking of the macromolecules. Y-type recombination of the per¯uoro-alkyl radicals ÐCF 2 .

and ÐCF 2 CF . CF 2 Ð is the most likely way that the crosslinking process occurs. The relatively high mobility of the elastomeric chains at room temperature allows the radical to recombine.