Abstract:Polyurethane prepolymer(PPU) was synthesized with isophorone diisocyanate(IPDI), poly(1,4-butanediol adipate) diol(PBA2000) and 2,2-dimethylol propionic acid(DMPA). Partially blocked hydroxy silicone oil(MPSi) was used as a hydrophobic end-capping agent, and the same molar amount of glycine(Gly) as MPSi was used as a hydrophilic end-capping agent to jointly cap PPU to synthesize a mixed-capped water-based polyurethane(MEPU) with pro-/hydrophobic chain end. The effects of r value〔n(IPDI)∶n(PBA2000)〕, DMPA content(based on the total quality of IPDI and PBA2000), and MPSi content(based on the total mass of the PPU) on MEPU performance were studied. The results showed that when r=3.0, w(DMPA)=5%, w(MPSi)=15%, MEPU emulsion is stable and transparent, compared with un-modified waterborne polyurethane, the water absorption rate of the MEPU decreased from 16.7% to 9.5%; water contact angle increased from 74.5° to 92.6°; initial decomposition temperature increased from 264℃ to 293℃; tensile strength increased 0.11 MPa; elongation at break increased by 5.81%. The water resistance and heat resistance of the film are significantly improved with the basis of not changing the stability of the emulsion.