Preparation And Properties Of PBT/epoxy Vitrimer Alloy

Polybutylene terephthalate（PBT）is widely used in all walks of life due to its excellent performance,but it’s recycling rate is low,which does not conform to the current concept of low carbon and environmental protection.Therefore,research on easy recycling High-performance PBT composite materials are a subject of great research value.Vitrimer is a new type of polymer with a dynamic cross-linked network structure.Under high temperature conditions,the dynamic cross-linked network reacts quickly to change and rearrange topological structure of the network,thereby making the material reshaped performance and re-workability,this performance makes the vitrimer material’s application prospects very broad.In this study,PBT/epoxy vitrimer alloy was prepared by blending extrusion reaction using bisphenol A diglycidyl ether,adipic acid,polybutylene terephthalate,and zinc acetylacetonate as raw materials,and crystallized,Research has been conducted to provide technical support for high-performance,re-plasticity,and easy-to-recycle PBT.The main work is as follows:（1）Preparation of epoxy vitrimer:Using bisphenol A diglycidyl ether and adipic acid as raw materials,with zinc acetylacetonate as transesterification catalyst and without catalyst,epoxy vitrimer containing dynamic covalent bonds was prepared.Infrared spectroscopy test showed that the characteristic peak of epoxy functional group in epoxy vitrimer disappeared at 915cm^-1,indicating that the hydroxyl transesterification was completed;DSC and DMA tests showed that epoxy vitrimer glass transition temperature was 51℃;mechanical property test showed that epoxy vitrimer fractured the elongation is 144%,and it has good toughness.The reaction kinetics study shows that the activation energy of epoxy vitrimer is 72.24KJ/mol without the action of catalyst.（2）The PBT/epoxy vitrimer alloy was prepared by the blending extrusion reaction method,and its melting behavior and crystallization kinetics were studied by differential scanning calorimetry.It was found that as the content of epoxy vitrimer increases,its melting point is getting lower and lower.When the content is 40wt%,its melting point is 192.1°C,which is 31.7°C lower than that of neat PBT.At the same time,it was found that as the content of epoxy vitrimer increased,the degree of transesterification gradually increased,which destroyed the regularity of the molecular chain and reduced the crystallization rate.The Avrami-Jeziorny method analysis shows that the Avrami constant n of PBT/epoxy vitrimer alloy has decreased relative to neat PBT,from 4 to 2～3,indicating that the crystal growth mode of PBT/epoxy vitrimer alloy is from spherulites to flakes.The crystal transformation was verified by observing the crystal morphology through a polarizing microscope.The Mo method analysis shows that the higher the epoxy vitrimer content,the larger the F（T）,which indicates that the crystallization rate of the PBT/epoxy vitrimer alloy is slower.（3）The PBT/epoxy vitrimer alloy was prepared by in-situ solid melting method,and the phase structure,melting behavior and crystallization kinetics of the alloy were studied by SEM,DMA,TGA,DSC and other techniques.SEM observation shows that PBT,bisphenol A diglycidyl ether and adipic acid form a homogeneous vitrimer alloy;DMA results show that the Tg of PBT in the PBT/epoxy vitrimer alloy shifts to the low temperature direction,indicating that the in-situ PBT/epoxy Vitrimer alloy has good compatibility;thermogravimetric analysis shows that as the content of epoxy vitrimer increases,the carbon residue rate also increases,that is,the dynamic cross-linking structure will increase the thermal stability of PBT;compared to in-situ PBT/Epoxy vitrimer alloy crystallization kinetic analysis shows that epoxy vitrimer has a negative effect on the crystallization rate of PBT,and affects the nucleation process of PBT.The Jeziorny method shows that the n value is close to 3,which is a three-dimensional heterogeneous nucleation.The growth of spherulites is consistent with that observed by polarized light microscope.（4）Preliminary research on the re-plasticity of PBT/epoxy vitrimer alloy by means of intrinsic viscosity and DMA.The study found that the intrinsic viscosity of neat PBT extruded multiple times gradually decreased.The intrinsic viscosity of PBT/epoxy vitrimer alloy did not change much,and its modulus did not change significantly.The results showed that dynamic crosslinking was formed between PBT and epoxy vitrimer.Bond,so that the performance of PBT/epoxy vitrimer alloy can be restored to its original state after multiple extrusion processing.