Preparation And Performance Studies Of Epoxy Vitrimer And Epoxy/PMMA Composite Vitrimer

Vitrimer polymer materials containing dynamic covalent bonds combine the good properties of thermosetting resins and thermoplastic resins and has broad application scenarios in the fields of shape memory,repeated processing and plastic recycling.In-depth research on the synthesis and preparation of vitrimers and the relationship between microstructure and properties has important guiding significance for improving material structure design and optimizing processing technology.In this paper,by adjusting the type of curing agent and the ratio of epoxy/carboxylic acid,a series of epoxy-based vitrimer and epoxy/PMMA composite vitrimer materials were prepared and their properties were studied.The research results obtained are as follows:(1)For changing the type and ratio of curing agent,the research shows that:4-4’dithiodibutyric acid(DA)with carboxylic acid or anhydride mix-curing epoxy can introduce double dynamic covalent bonds,stimulate dynamic transesterification and disulfide bond exchange reactions at high temperatures,accelerate the stress relaxation rate,and reduce the material glass transition temperature and topological freezing transition temperature(T_v),endow the material two-way shape memory properties;the long and flexible chain structure of the curing agent DA also has an excellent toughening effect.(2)The research on the preparation of epoxy vitrimer under non-stoichiometric ratio shows that under the action of transesterification catalyst1,5,7-triazidebicyclo[4.4.0]dec-5-ene(TBD),a permanent cross-linked polyether network can be generated for the excess epoxy,which effectively improves the mechanical strength and thermal stability of the vitrimer;the characteristic length(ξα)of the cooperative rearrangement regin(CRR)decreases with the increase of the amount of epoxy.(3)The research on epoxy/PMMA composite vitrimer material shows that:the existence of PMMA side ester group can promote the transesterification reaction of the system,improve its repeated processing efficiency,and increaseξα;with the increase of PMMA content,PMMA in epoxy vitrimer exists in the form of miscible-slightly soluble-phase separation.In the state of slightly soluble,the composite material with the highest mechanical strength and the strongest toughness can be obtained.