Evaluation of the Fracture Behaviors of Fluoropolymer Binders with the Essential Work of Fracture (EWF)

摘要

As one of the most appropriate techniques for evaluating the fracture behavior, the essential work of fracture (EWF) was firstly introduced to investigate the fracture behaviors of fluoropolymer binders with different molecular structures used in polymer bonded explosives.The molecular motions of four selected fluoropolymers were measured by dynamic mechanical analysis (DMA).The incorporation monomers of chlorotrifluoroethylene (CTFE),tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), would retard the molecular mobility of vinylidene fluoride (VDF) chain, causing the glass transition temperature (Tg) shifted to a higher value.Through EWF testing, the effect of molecular structure on the fracture behaviors of fluoropolymer binders was investigated.The specific essential work of fracture, we, decreased with Tg increasing, while the specific plastic defomation work, βwp(1), had an opposite change trend.In addition, by fracture energy partitioning, the energy distribution during the fracture process of fluoropolymers was found out.The dominant factors which affected we and βwp for the studied systems were the necking terms, as a majority of fracture energy was dissipated in the necking and fracture process.