Effect of chemical structure and molecular weight on high-temperature stability of some Fomblin Z-type lubricants

High-temperature stability of a series of Z-type PFPE lubricants with different MW and end-groups have been studied by TGA, GPC, and FT-IR. It was found that, in air and at elevated temperatures, the weight-loss of low-MW Zdols is due to evaporation while the weight-loss of high-MW Zdols is initiated by thermal oxidative decomposition. The experimental results also show that the end-groups have a significant effect on the decomposition mechanism. For Zdols that have hydroxyl end-groups, the initiation of decomposition reaction is oxidative in nature. For Zs that have perfluoromethyl end-groups, the decomposition is a thermal depolymerization reaction.