Abstract
PDMS (polydimethylsiloxane) can be generated from cyclic oligomers such as D4, cyclotetra(dimethylsiloxane), by the ring opening polymerization process. The reaction is reversible and is catalyzed by a proton or an alkaline ion in either direction. The catalyst ions may remain trapped in the product polymer. Thus on warming, depolymerization could occur leading to emanation of the vapor of cyclic oligomers. The intramolecular disproportionation reaction of PFPE (perfluoropolyether) catalyzed by a Lewis acid center (e.g. those formed on nascent aluminum oxide surface) generates fragments possessing an acylfluoride end group, R-C(=O)F which readily converts to the acid form, R-C(=O)OH. It is postulated that the siloxane smear observed on disk surface is due to that generated by repolymerization of the oligomer (emanated from PDMS containing parts) catalyzed by the acid resulting from the PFPE lubricant degradation.
