Study On The Design,Synthesis And Performance Of Polyester And Vitrimer Materials Based On Citric Acid

Polymer materials mainly include thermoplastic materials and thermoset materials,among them,the main structure of thermoplastic materials is mainly composed of linear segments,which can be reshaped at high temperature.Thermosetting polyester material is mainly composed of cross-linked network to form its main structure,it is a one-time forming and non-reproducible material,It could be cause a lot waste of resources.As we all know,most of the existing polymer materials come from petroleum,which is not be renewable with increasingly scarce.Therefore,we carry out the following work to solve these problems.1.Polyethylene terephthalate(PET)is an important classification of polyester materials,It is a petroleum-based polymer material,It always play an important role in daily life,medical industry,construction production,automobile field,etc.But its low T_g value limits its application range,Cause a waste of resources.Adding rigid monomers can prepare high T_g materials.We use the Weiss-Cook reaction of diethyl acetone dicarboxylate,a citric acid-based monomer,and diacetyl,the rigid monomer3a,6a-dimethyloctahydropentene-2,5-diol(DOPD)was obtained by reduction with sodium borohydride.The series polymer PD_xE_yT was successfully prepared by using this monomer,ethylene glycol and dimethyl terephthalate.The rigid diol monomer was subjected to hydrogen nuclear magnetic resonance spectroscopy,carbon spectroscopy,and X-ray single crystal diffraction for structural characterization.For the series of polymer PD_xE_yT,its structure was characterized by hydrogen nuclear magnetic resonance spectrum,infrared spectrum,GPC,etc.TGA was used to characterize its thermodynamic stability.DSC was used to characterize its thermal behavior.The conclusion is 3a,6a-Dimethyloctahydropentene-2,5-diol(DOPD)rigid diol has three isomers,The addition of rigid glycol in the polymer can significantly increase the T_gvalue.2.In recent years,vitrimer materials have been greatly developed,as we know generally the reaction effect is achieved by adding a catalyst,The catalyst will leak in the later use of the material and cause immeasurable consequences.The development of catalyst-free materials is imminent.In this chapter,a series of ester-based catalyst-free vitrimer materials were successfully prepared by transesterification between dimethyl acetone dicarboxylate and pentaerythritol with cyclohexanedimethanol,cyclohexanediol,and hexanediol,respectively.Use infrared spectroscopy,swelling rate,etc.to characterize its structure.Use TGA to characterize its thermal performance,Use DSC to characterize its thermal behavior.The transmittance is characterized by an ultraviolet spectrophotometer,Tensile strength test to characterize its mechanical properties,SEM was used to characterize its material properties.The results showed that the vitrimer material was successfully synthesized by transesterification,with transparency above 90%,stable thermal performance,good thermal behavior,good tensile strength,elongation at break and elastic modulus.Some of the materials still maintain good mechanical and thermal properties after repeated processing for 5 times.The surface of the material is consistent with the tensile properties.3.This chapter uses dimethyl acetone dicarboxylate,pentaerythritol and green energy glycerol to synthesize vitrimer materials.Mainly study the influence of the internal hydroxyl of the material on the material performance.The glycerol-based vitrimer material was characterized by infrared spectroscopy,gel content-swelling rate,ultraviolet transmittance,TGA,DSC,stress-strain and other properties.The results show,Glycerol-based vitrimer was successfully synthesized,the material has high transparency,The higher content of hydroxyl in the material can affect the thermal stability and mechanical properties of the material to a certain extent.