Preparation and Properties of Bio-based Schiff Base Self-repairing Polyurethane
Dynamic covalent bonds were a type of chemical bond that can be broken and restored under specific conditions.Among them,Schiff base was a dynamic covalent bond formed by the condensation of aldehydes and amine compounds.A bio-based Schiff base compound(MV/S)was synthesized by the reaction between the amine group of 1,8-p-menthanediamine(MD)with the aldehyde group of vanillin.A Schiff base compound(EV/S)without aliphatic ring was synthesized by replacing MD with ethylenediamine.Using MV/S and EV/S as chain extenders,the self-healing Schiff base polyurethane films(PU/SM and PU/SE)were prepared,At the sametime,the polyurethane without Schiff base(PU/BDO)prepared without MV/S and EV/S was used as a blank control to determine the effect of MD on the properties of self-healing polyurethane.Various analytical and testing methods were employed to study the structure,mechanical properties,and self-healing performance of the polyurethanes.The results showed that the tensile strength of PU/SM was 30.7 MPa,which was 20.1 MPa higher than that of PU/BDO.TG/DTG analysis revealed that the introduction of MD significantly improved the heat resistance of PU/SM.Comparison at the same temperature showed a significant reduction in relaxation time of PU/SM compared to that of PU/SE,indicating that the introduction of MD promoted the exchange rate of dynamic covalent bonds.Compared with PU/SE,PU/SM exhibited a faster relaxation rate,and the activation energy was reduced by 35.84 kJ/mol.The results of self-healing performance tests demonstrated that PU/SM had superior self-healing properties compared to PU/BDO and PU/SE,with a self-healing rate of 77%for the sheared PU/SM film after 24 h of heating at 80℃.
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