Microstructure Research Of Epoxy Vitrimer And Its Carbon Nanotube Composites During Glass Transition

Vitrimer has properties of both thermosetting and thermoplastic,making it widely used in self-healing repeatable machining and shape memory.Understanding the microstructure of these materials during the glass transition process is of great significance for improving the molecular design,improving the properties and optimizing the processing conditions.In this paper,by characterizing the characteristic length of cooperatively rearrangement regions(CRRs)of epoxy vitrimer and epoxy vitrimer/carbon nanotubes(CNTs)nanocomposites during the glass transition process,the research results are as follows:(1)The study on the characteristic size of CRR during glass transition of epoxy vitrimer shows that catalyst is the decisive factor to determine the size of CRR.The higher the catalytic efficiency of ester exchange catalyst,the smaller the crosslinking density(ν_e)of epoxy vitrimer and the larger the characteristic length(ξ_α)of CRR.When the glass transition occurs,the corresponding glass transition process is wider.The molecular chain structure of hardener also has significant effect onν_eandξ_α.The longer the curing agent molecular chain,the smaller theν_eandξ_α,and theξ_αof epoxy vitrimer,the narrower the glass transition process(2)The study of CRR characteristic size of epoxy vitrimer/carbon nanotube(CNT)nanocomposites during the glass transition shows that the content of CNT has a significant effect on the CRR size of epoxy vitrimer/CNT nanocomposites during the glass transition.The addition of CNT increases the CRR in all vitrimer/CNT glass transitions,and the CRR increases first and then decreases with the increase of CNT content.The effect of carboxylated carbon nanotube(FCNT)on CRR is related to the carboxylation time of carbon nanotube.With the extension of carboxylic time,the CRR of epoxy vitrimer/CNT glass transition decreases first and then increases.