Mechanical scission of perfluoropolyethers

Abstract

Mechanical scission of two typical perfluoropolyethers was investigated: Y, a copolymer of CF(CF3)CF2O, CF2O, and CF(CF3)O, and Z, a copolymer of (CF2)nO, with n = 1,2,3,4. Undiluted polymers were subjected to prolonged shearing in a media mill with ZrO2 particles. A chemical extraction of the polar ZrO2 particles was carried out to collect adsorbed polar scission products. Mechanochemical scission products from both the Y and Z fluorocarbon polymers were identified by 19F‐NMR. A significant amount of CF3CO2− was present after the milling and the primary functional groups formed at scissioned chain ends were CO −2. A hydrodynamic expression was derived and the maximum extension rate was estimated to be in the range of 5 × 106 s−1. Initial degrees of polymerization were between 20 and 200, well below levels for which flow‐induced scission is expected to occur. Final degrees of polymerization were less than 10, and the scission was noncentral and nonrandom in both polymers. © 1993 John Wiley & Sons, Inc. Copyright © 1993 John Wiley & Sons, Inc.