Preparation Of Self-Healingwaterborne Polyurethane And Itscoating Properties

Inspired by nature,self-repairing materials with damage and self-repairing ability have attracted much attention because of their potential to improve the reliability,durability,and life of materials.However,the poor self-healing performance of self-healing waterborne polyurethanes(WPUs)in the ambient environment severely hinders their wide applications.In this dissertation,two self-healing waterborne polyurethane systems were designed and synthesized by self-emulsification method.In the first system,in order to break through the limitation of chain stiffness and improve the self-healing ability of WPU,glycylglycine methyl ester(GGMe)was selected as the functional dipeptide end-capping reagent of WPU molecular chain to form triple hydrogel bonds at the end of the chain.WPUG elastomers were prepared by self-emulsification method with PTMG as the soft segment,IPDI as the hard segment,DMPA as the hydrophilic chain extender,TEA as the neutralizer and GGMe as the end-capping agent.The effects of chain-end hydrogen bonds on the transparency,thermal properties,mechanical properties and self-healing properties of WPU capped with the capping agent GGMe were investigated.The results showed that GGMe was introduced into the main chain of WPU in the form of end-capping,and the ratio of soft and hard segments in the polyurethane was adjusted by changing the molar mass(mmol)of the end-capping agent GGMe.It was found that the chain-end triple hydrogen bonds play a unique role in WPUG,which can serve as a "bridge" to connect soft segments,endowing the molecular chain with more flexibility and fluidity.As a result,the self-healing efficiency of WPUG in the surrounding environment can reach 91.5% within a short time.The mechanical properties of polyurethane are crucial for various applications,so in order to improve the mechanical properties of polyurethane,in the second system,NDI with π-π conjugation and rigid structure was selected to partly replace IPDI as a hard segment,the N-WPUG composite coatings were successfully prepared through drop coating.The effects of the addition of NDI on the contact angle,mechanical properties,self-healing properties,and fluorescence properties of the coatings were investigated.The results showed that NDI was added to WPUG to prepare N-WPUG composite coating,which also showed good self-healing ability.The mechanical properties and contact angle of the coatings were also significantly improved.The introduction of naphthalene ring group in NDI increased the good fluorescence properties of WPUG and the N-WPUG composite coating could emit strong blue fluorescence under the irradiation of 365 nm UV lamp.The N-WPUG composite coatings with the self-healing and fluorescent properties shows big potential to be anti-counterfeiting materials in the future.