Thermal degradation and thermo-oxidative aging behavior of vinylidene fluoride-containing fluoroether rubber

Abstract

Vinylidene fluoride-containing fluoroether rubber has better low temperature performance, expansion resistance and heat resistance. After curing by peroxide, it can be applied to a variety of fuel mixtures and is expected to be widely used in aerospace as a sealing material or other fields. In this work, the thermal degradation and thermo-oxidative aging behavior of Vinylidene fluoride-containing fluoroether rubber cured by 2,5-dimethyl-2,5-di-(tert‑butylperoxy) hexane/Triallyl isocyanurate (DBPH/TAIC) were investigated. For comparison, raw rubber without any crosslinking has been taken. The results indicated that the thermal degradation of vinylidene fluoride-containing fluoride rubber started with the degradation of TAIC in addition to the removal of HF on the backbone and the breakage of the side chain of ether monomers. During thermo-oxidative aging, the main chain formed C = C structure under the mechanism of dehydrofluorination. Meanwhile, the molecular chain broke under the action of thermal oxygen and was accompanied by the formation of carbonyl groups. The destruction of the polymer cross-linked structure occured at the TAIC cross-linking point and mainly occurred in the early stage of aging. However, the crosslinking was not completely disrupted, as the crosslinking density increased with aging time. The destruction and recombination of the crosslinked structure occurred simultaneously during the whole aging process and were dominated by recombination. Over-crosslinking after aging reduced the tensile properties of composites. This work contributes to a better comprehending of the stability of fluoroether rubber seals in a thermal-oxygen environment.