Vinylidene Fluoride / Chlorotrifluoroethylene Copolymer Microstructure And Properties Of Study

A series of VDF/CTFE copolymers that have a lower content of CTFE were synthesized by radical copolymerization using BPO as initiator and F113 as solvent. The microstructure of copolymer was characterized with GPC, NMR, Elemental Analysis, FTIR and DSC, the effect of CTFE content was also investigated. The differeneces between the copolymer composition and the reagents' ratio were further discussed.The crystallinity degree and crystallization property were studied with the X-ray diffraction spectrum by computer simulation, meanwhile, the thermodynamics of the copolymers were investigated by the dynamic mechanical analysis, the effects of CTFE content in the copolymers on the microstructure and mechanical properties were discussed, the stiffness, viscoelastic behaviors and damping properties of the copolymers were comparative analyzed, the research results show that:(1) In the copolymerization that uses F113 as solvent, there is a dissolution equilibrium of the reagents in solvent. F113 is the raw material to prepare CTFE, which shows that it has a significantly dissolubility of CTFE under pressure. The copolymerization destroys the equilibrium, which increase the CTFE' content in the reaction system, the content of CTFE in the copolymers is significantly higher than the reaction system. With the NMR and FTIR, the key joint structure of structural units in the chains changes a lot, along with the increase of CTFE content, there is a decrease of VDF-VDF link, while a increase of VDF-CTFE link. The random distribution of VDF-CTFE link affects the crystallinity of the copolymers seriously.(2) The contents of VDF-CTFE link and VDF-VDF link change along with the variation of CTFE, it has a significant effect on the crystallinity of the copolymers. The copolymer is amorphous when the content of CTFE is above 35%. The major crystal in the copolymer is the VDF crystal and the crystal plane is (010) and (101).(3) The stiffness of copolymer under Tg is affected by the crystallization behavior, while in the amorphous copolymers the increase of CTFE improve the stiffness, and the chain segment length distribution gets smaller. There is no secondary transition in the copolymer with the DMA, the damping of the copolymer increases along with CTFE content in the transition of semi-crystalline copolymer to amorphous copolymer.