Snythesis And Properties Of Self-Healing Polyurethane Based On Biomass Polyphenols

Thermosetting polyurethane is extensive used in coating and adhesive because of the thermal stability and solvent resistance.With the increasing industrial demand of polyurethane year by year,a mass of dumped polyurethane materials were generated.Since the stable crosslinking network of thermosetting polyurethane makes it implastic and unrecoverable,which leads to resource waste and environmental pollution.Inspired by the reversible reaction between the phenolic hydroxyl and isocyanate,this project is plan to prepare the self-healing and recyclable thermosetting polyurethane by natural polyphenol croaalink reversible with isocyanate.Different polyphenol can be compounded the different self-healing thermosetting polyurethane,and how to the polyphenols with different substituent and the ration of hard and soft chain segment influence the performance of self-healing polyurethane are worth exploring.At first,based on propyl gallate(PG)and the Polyurethane pre-polymer(PTHTTDI),selfhealing thermosetting polyurethane was prepared.The chemical structure and the cross-link network were confirmed by Fourier Transform Infrared Spectroscopy(FT-IR)and the swelling tests.Meanwhile,the samples partially dissolved in trichlorobenzene when the temperature risen to 120 oC,this temperature is correspond to the unusual trend on the tan? and storage modulus curves after the plateau above 120 oC by the Dynamic mechanical analysis(DMA).Variable-Temperature FT-IR were performed to confirm the phenolic urethane was disconnect begin 120 oC,it can be explained the experimental phenomenon occurred in swelling test and DMA.The optimum temperature for self-healing is 132.6 oC,which was calculated by the Differential Scanning Calorimeter(DSC).The broken and healed thermoset reserved about 70% of tensile strength and 86% of elongation at break of the original material by Tensile properties analysis.Polyphenols with different substituent can observably impact the properties and selfhealing abilities of the polyurethanes.To further investigate the impact,different substituent groups of polyphenols(Catechol,Propyl gallate,Urushiol,Tert-butylhydroquinone)were used to evaluate their reaction with isocyanate pre-polymer in this study.The chemical structure of polyurethanes were confirmed by FT-IR.Differential scanning calorimeter(DSC)indicates that the reaction temperature of the four polyurethanes is in the following order: PTHFTDIUrushiol<PTHFTDI-Catechol<PTHFTDI-Propyl gallate<PTHFTDI-Tert-butylhydroquinone.PTHFTDI-Tert-butylhydroquinone is not an elastomer but a viscoelastic resin,it can't be applied for the research of self-healing.The decomposition temperature of PTHFTDI-Urushiol? PTHFTDI-Catechol?PTHFTDI-Propyl gallate measured by Variable-Temperature FT-IR were 130 oC,150oC and 120 oC,respectively.The thermal stability of the three self-repairing polyurethane is not very different,and PTHFTDI-Urushiol is slightly higher.At the same temperature,the healing ability of the three polyurethanes is in the following order: PTHFTDICatechol<PTHFTDI-Urushiol<PTHFTDI-Propyl gallate.Based on the reversible reaction between phenolic hydroxyls and isocyanante,and selfhealing polyurethane could be synthesized by isocyanante and phenolic hydroxyls instead of alcoholic hydroxyls.The five different performancepolyurethane were compounded from the different ratio of propylgallate which contains hard segment and urushiol which has the soft long chain.The chemical structure,thermoset stability,mechanical properties and the ability of self-healing were analyzed by FT-IR ? TGA ? DMA and tensile properties analysis.The increasing ratio of urushiol can enhance the polyurethane thermal stability but reduce the Tg and storage modulus to some extent.The mechanical properties of polymer will decrease with the increasing ratio of urushiol,and the highest self-healing ability of tensile strengthen can get at-OH(prolpy gallate):-OH(urushiol)=1:1.