Effects of the Double Bond Content in Soft Segments on the Properties of Waterborne Polyurethane
Waterborne polyurethane(WPU)has the disadvantages of low mechanical properties and large permanent deformation due to its low molecular weight,which limits its applications in the field of high-performance materials.In order to improve the deformation recovery ability and mechanical properties of WPU,a series of waterborne polyurethane(WPU)with different double bond contents in soft segments were synthesized by using polypropylene glycol(PPG),hydroxyl-terminated polybutadiene(HTPB),isophorone diisocyanate(IPDI),4,4′-diphenylmethane diisocyanate(MDI),2,2-dimethylol butyric acid(DMBA)as raw materials and stannous octoate as the catalyst.Ammonium persulfate(APS)was used as a double bond initiator to initiate the reaction between double bonds in the soft segments of polyurethane to achieve the cross-linking of polyurethane molecular chains,ultimately preparing waterborne polyurethane films with different cross-linking systems.The structures of the films were characterized by Fourier transform infrared spectroscopy(FTIR),proving the introduction of soft segment double bond.At the same time,the mechanical properties of the film are improved after crosslinking,the glass transition temperature of the soft segment decreases first and then increases after crosslinking,and the glass transition temperature of the hard segment decreases.The results show that when the ratio of n(HTPB)and n(PPG)is5∶53,the tensile strength of the waterborne polyurethane film reaches24.06 MPa,the elongationat breakis780%,and the deformation recovery rate is 93.8%.
Polyurethane ElastomerDouble Bond in Soft SegmentDeformation Recovery RatioInitiating SystemMechanical Property
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