Cross-linked Polyurethane By Bisphenol Chain Exetension And Its Self-healing Property By Phenol Hydroxyl Deblocking Reaction

Due to its excellent physical and chemical properties,polyurethane has been applied more and more in people's daily life and industry.However,it will inevitably appear a variety of damage during the using time.If these damages are not repaired in time,the mechanical properties of materials will decline and the service life of materials will be greatly shortened.Self-healing polyurethane materials was studied in these years to solve these problems.The common self-healing methods are to realize the self-healing function of materials by introducing thermal reversible bonds.These methods of repair without adding catalysts,repair agents,and could be in the same location for multiple repair,so they have gained more and more attention.Diels-Alder reaction healing mechanism and disulfide bond healing mechanism are the most studied ways to realize the self-healing process.However,the development of self-healing polyurethane materials is limited due to the single type of raw materials and monomers required by these repair mechanisms,high price and complex synthesis process.In this paper,we design a novel self-healing network via incorporating reversible urethane bonds into polyurethane materials.The key element of this self-healing strategy is found in the blocking and deblocking reaction of diisocyanate in urethane bond.Blocking agents are widely used to protect isocyanates.At high temperature,because of deblocking reaction,urethane bonds can cleave into isocyanate and hydroxyl groups,and reduces the molecular weight,enhances the kinetic ability of the molecular chain,and restores the damage.At low temperature,isocyanate and hydroxyl groups will reform urethane bonds again.As compare to other self-healing cross-linked polymeric system,self-healing of polyurethanes can be easily achieved by the interaction between diisocyanate and chain extender without the need of further monomer synthesis.Furthermore,The structure of the synthesized product is similar to that of polyurethane,which can maintain the properties of polyurethane to the greatest extent.The main work and results of this paper are as follows:(1)TBBPA-MDI and BPS-MDI polyurethane prepolymers were synthesised by reaction of TBBPA/BPS and MDI.The structure of TBBPA-MDI and BPS-MDI was studied by FT-IR,NMR and GPC.The prepolymers was conducted by FT-IR to study the deblocking behavior of TBBPA-MDI and BPS-MDI.The results show that TBBPA-MDI and BPS-MDI has the characteristics of deblocking behavior.(2)TBBPA and BPS were used as chain extenders respectively,and the GL was added to prepare the self-healing cross-linking polyurethanes(Sh-C-PUTBBPA and Sh-C-PUBPS),and the thermal reversible behavior of the product Sh-C-PUTBBPA and Sh-C-PUBPS was studied by FT-IR.The results show that Sh-C-PUTBBPA and Sh-C-PUBPS exhibited deblocking behavior with the increase of temperature.In the process of cooling,the blocking characteristic will be shown,and the thermal reversibility characteristic will be shown in the process of cyclic heating and cooling.(3)In order to determine the cross-linking structure of Sh-C-PUTBBPA and Sh-C-PUBPS,and to determine the deblocking behavior of the product,the swelling property of Sh-C-PUTBBPA and Sh-C-PUBPS was studied.Sh-C-PUTBBPA and Sh-C-PUBPS showed cross-linkable structure and good deblocking property.(4)The self-healing performance of Sh-C-PUTBBPA and Sh-C-PUBPS was studied by using POM and universal testing machine.The results showed that under the observation of POM,Sh-C-PUTBBPA and exhibited great healing property.According to the results of healing efficiency,With the increase of healing times,the healing efficiency of Sh-C-PUTBBPA is 97.82%the first repair,the second healing is so high as 86.38%,and the third is 55.04%.With the increase of healing times,the healing efficiency of Sh-C-PUEPS was 77.91%the first repair,the second was 38.36%,and the third was 16.51%.