Synthesis And Room Temperature Self-healing Performance Of Crosslinked Polyurethane

Intrinsic self-healing system is mainly to repair the damaged materials by polymer intermolecular non-covalent interaction and covalent interaction,healing injury under the external stimulation automatically,restoring the integrity of the mechanical properties partially or completely.In contrast,covalent interactions is greater than non-covalent bond.Dynamic covalent fracture and formation in suitable conditions reversibly,combined with the stability of the non covalent reversible and covalent bonds.Diels-Alder(DA)reaction is a dynamic reversible covalent chemistry reaction based on temperature.Its mild reaction condition,high yield,less side reaction,and no extra the catalyst,and thermally reversible make it widely apply to self-healing polymer;The low bond energy of the disulfide bond and the reversible exchange equilibrium reaction provide the possibility for the self-healing polymer materials under mild conditions.The Diels-Alder(DA)and disulfide bond have the characteristic of reversible exchange and relative mild transformation conditions,this paper mainly studies the the reversible exchange Diels-Alder(DA)and different types of disulfide bonds in crosslinked self-healing polyurethane.Specifically,the work of this paper includes the following aspects:1,first of all,the molecular chain structure of polyurethane was designed.By the pre-polymerization process,a new type of crosslinked polyurethane(CPU-DA)was prepared,with DA bonds as the crosslinking points.By using Fourier transform infrared spectrometer(FT-IR),differential scanning calorimetry(DSC),optical microscope,electronic universal testing machine,thermal reversible properties of Polyurethane Prepolymer and desired product of polyurethane were studied.Theresults show that CPU-DA has the characteristics of rapid self-healing and multiple reprocess.When heat at 110 ?for 10 minutes,the repair of crack healing efficiency is81.6%;crush down and reprocess for three times,the tensile strength only did not fall after three times,but increased more than 65%.It increased from 8.56 MPa to14.14 MPa.2,disulfides were obtained by oxidizing sulfhydryl compound with sodium periodate and hydrogen peroxide.the disulfide thiol oxidation for;By three triethylamine as catalyst,with iodine as oxidizer,using ethyl hydroxyethyl amine and carbon disulfide to get thiuram disulfide monomer;by pre-polymerization method respectively containing disulfide bonds of two different types of monomers(alipHatic disulfide monomer and thiuram disulfide monomer)into polyurethane materials,which disulfide bonds with low bond energy isr crosslinking points.using FT-IR to study the chemical structure and composition of self-healing polyurethane.By tensile test and contrast test method,self –healing efficiency of disulfide bond and hydrogen bond in the self-healing process is analyzed.The results show that the prepared crosslinked polyurethane with alipHatic disulfide bond can be used to achieve high self –healing efficiency at room temperature without additional catalyst and external stimulation conditions.The specimen was cut into two halves with a blade,then being placed close to the natural light for 48 hours,the tensile strength could be restored to 95% of the original,and the elongation at break was restored to 100% of the original.Among them,the hydrogen bond provides about 30%self-healing efficiency which formed between the urethane bond of polyurethane.TMN50-PPG50-DHTD has good self-healing properties,The specimen was cut into two halves with a blade,then being placed close to the natural light for 24 hours at room temperature,the tensile strength could be restored to 69% of the original,the visible light has contributing to self-healing.under visible light after reaching for 24 hours,the self-healing efficiency can attain 81%.