Preparation And Characterization Of Self-healing Polymer Materials Based On Hydrogen Bond

Polymers and their composites are widely used in transportation,electronics,construction,aviation,aerospace,medical,machinery and other fields due to their excellent properties and their unique advantages in terms of applicability,portability and flexibility.In actual use,polymers and their composite are susceptible to external factors such as mechanical,chemical,thermal,and ultraviolet radiation,which can cause performance degradation or even failure,thereby greatly shortening the service life of the device and even causing certain safety risks.Endowing materials with self-repair capabilities can greatly enhance device reliability,extend device life,and reduce potential safety hazards.At present,there are many kinds of self-healing materials,which can be divided into intrinsic and extrinsic type according to healing mechanisms.Among them,dynamic reversible hydrogen bonding,as one of the intrinsic healing methods,has great significance for the design and preparation of polymers materials that can be repaired multiple times at room temperature.Therefore,in this work,based on dynamic reversible hydrogen bonding,two different self-repairing polymer composites were designed and prepared,and their mechanical,self-healing and electrical properties were studied.(1)A polyurethane composite conductive material containing 2-ureido-4 [1H] pyrimidone(UPy)groups in the main chain was studied.Polytetrahydrofuran(PTMG)with good flexibility was selected as the soft segment and the UPy group,which can form multiple hydrogen bonds,has high thermodynamic stability and fast dynamic reversibility,was used as the hard segment,to prepare the polyurethane substrate with UPy in the main chain.Then a PU-UPy / CNT self-healing polymer composite conductive was prepared by a spray process.The molecular structure and micro-morphology of PU-UPy / CNT materials were characterized by NMR and SEM.The mechanical,electrical and selfhealing properties of the composite film were also studied,and the results showed that the composite films prepared from PU-UPy materials with a concentration of 50-150mg/ml had excellent properties of good tensile length(>1000%)and self-healing without external stimuli at room temperature.The PU-UPy/CNT composite conductive film obtained by spraying also has good conductive properties.After undergoing multiple cutting-healing cycles,conductivity can be restored(resistance changes within an order of magnitude after three cutting-healing cycles).A self-healing model of composite films was established,and its healing mechanism was analyzed and explored.In addition,the application of PU-UPy/CNT composite film as a strain sensor achieves the preliminary detection of small strain human body motions.(2)The self-healing composites based on PAA-PAM polymer hydrogels were studied.PAA-PAM hydrogels were prepared by a simple copolymerization method.The effects of copolymerization ratio of acrylic acid and acrylamide monomer on its mechanical properties and self-healing properties were investigated,and the results showed that PAA-PAM hydrogels obtained by copolymerizing acrylic acid and acrylamide monomers of the same quality had the best mechanical properties(tensile ratio ~ 50%,tensile strength ~ 23.2kPa and small hysteresis curve)and self-healing properties.On this basis of PAA-PAM hydrogel,PAA-PAM/TA hydrogel was prepared by compounding tannic acid(TA)as a self-healing and mechanical reinforcement material.It has high mechanical tensile strength of 55.8kPa,good tensile length ~ 140%,small hysteresis curve,fast self-healing speed(2min),high self-repairing efficiency(~ 90%),and can self-heal without external stimuli at room temperature.In addition,the self-healing mechanism of PAA-PAM and PAA-PAM / TA hydrogels was established by analyzing the hydrogen bonding network models inside them.