Study On Preparation And Self-healing Behavior Of Polyurethane Based On Thermoreversible Covalent Bond

The Polyurethane is widely used in the automotive,medical materials,aerospace and other fields because of its good mechanical properties,chemical resistance and weather resistance.However,in the processing and use process of polyurethane,the physical defects produced will affect the material use.Therefore,by simulating the self-healing characteristics of organisms,the repair of the microcracks in the material itself has been realized,and the service life of the material can be prolonged.In the present research,there are many self-repairing methods for the polymer materials,and the thermal reversible self-repairing method is an effective one.The Diels-Alder?DA?is a kind of cycloaddition reaction[4+2]taking place between the dienes and dienophiles,with the mild reaction conditions,high yield and few side reactions.Due to the special microphase separation structure and flexible molecular design of polyurethane,the maleimide groups can be introduced into the intermediate product end of furanyl polyurethane prepolymer?MPF?synthesized by the polyurethane to take place the cycloaddition reaction,thus endowing the polyurethane with the self-healing ability.In this paper,firstly,the two different hard segment types of linear self-healing polyurethanes?T-PU-DA,I-PU-DA?have been prepared by the reaction of the toluene diisocyanate?TDI?and isophorone diisocyanate?IPDI?with the polypropylene glycol?PPGMn=2000?and furfurylamine?FM?respectively.Secondly,the furfuryl glycidyl ether?FGE?has been prepared by the ring-opening reaction taking place between the epichlorohydrin and furfuryl alcohol under the certain conditions,and the product with the three furan groups?FGEFM?has been prepared by the reaction taking place between FGE and FM.Finally,the cross-linked self-healing polyurethane?I-CPU-DA?has been prepared by the reaction of the IPDI,PPG and FGEFM.The thermal stability,thermal reversibility and self-repairing behavior of the T-PU-DA,I-PU-DA and I-CPU-DA have been studied by the Fourier transform infrared spectrometer?FT-IR?,differential scanning calorimeter?DSC?,gas chromatograph?GPC?,thermo-gravimetric analyzer?TGA?,polarized light microscope?POM?,Gel-solution-Gel and mechanical tests.The main conclusions of this paper are as follows:1.Study on the repair behavior of linear self-repairing polyurethane:the FT-IR results have shown that the DA addition characteristic peak has been appeared at the1778cm^-1;the DSC results have shown that the T-PU-DA and I-PU-DA have no crystalline structure and show the high elastic state above the room temperature;the TG results have shown that there is no mass loss of the T-PU-DA and I-PU-DA at 40-150 ?;the GPC results have shown that the number-average molecular weight of the T-PU-DA and I-PU-DA decreases after the 10min of heat treatment at the constant temperature 120?,and the number-average molecular weight after the 10min of heat treatment at the constant temperature 60? is close to that of the samples without the heat treatment;the Gel-solution-Gel test has shown that the phase state of both the T-PU-DA and I-PU-DA is appeared as a fluid shape when the 10min of heat treatment at the constant temperature 120?,and gelatinous when the 180min of heat treatment at the constant temperature 60?,the number of heat reversible cycles of the I-PU-DA and T-PU-DA is 4 and 2,respectively.The tensile test has shown that the repair performance is the best when the F/M of the T-PU-DA and I-PU-DA is 1:1,after the24h of heat treatment at the constant temperature of 60?,the repair rate of T-PU-DA is 62%,and the repair rate of I-PU-DA is 71%,the higher the repair temperature is,the shorter the repair time is,a certain repair performance can still be maintained after the three times of damage in the same position;the POM observation has shown that the T-PU-DA and I-PU-DA could fill the crack after the 100min at the 100?.2.Research on the repairing behavior of cross-linked self-repairing polyurethane:The FI-TR study has shown that the DA addition characteristic peak has been appeared at the 1778cm^-1;the DSC results have shown that the I-CPU-DA has a wide absorption peak at the 50-150?;the TGA results have shown that the I-CPU-DA has no quality loss at the 40-150?;the swelling test has shown that only the swelling is occurred but no dissolution is occurred in the I-CPU-DA;the Gel-solution Gel test has shown that the phase state of I-CPU-DA is appeared as a fluid shape when the 10min of heat treatment at the constant temperature of 120?,and gelatinous when the 180min of heat treatment at the constant temperature 60?,the number of heat reversible cycles of I-CPU-DA is 7;The tensile test has shown that the repair performance is the best when the F/M of I-CPU-DA is 1:1,after the 3 hours of heat treatment at the constant temperature of 80?,the repair rate of I-CPU-DA is 82%,The higher the repair temperature is,the shorter the repair time is,a certain repair performance can still be maintained after the three times of damage in the same position;the POM observation has shown that the T-CPU-DA and I-CPU-DA could fill the crack respectively after the45min at the 100?.