A series of waterborne polyurethanes (WPUs)with 50% solid content were prepared through a prepolymer process.The properties of the dispersion and its film were characterized by Fourier transform infrared spectroscopy (FT-IR)

particle size analyzer

X-ray diffraction (XRD)

differential scanning calorimetry (DSC)and tensile test machine.The influence of HDI/IPDI mole ratio on the properties of waterborne polyurethane dispersion

its film and the adhesive strength to EVA/PVC substrate were studied.The relationship between adhesive strength and time was analyzed.The results indicated that the WPU dispersion

crystallinities of soft segment and hard segment were improved with increasing HDI/IPDI mole ratio

while tensile strength of films significantly increased and then showed a small decrease

and the elongation at break increased first

then decreased.WPU films exhibited excellent waterproof performance

and the amount of water absorption was as low as 5.0%（mass）.The test result showed that all WPUs prepared exhibited outstanding adhesive strength to EVA/PVC substrate

and the joint failure of EVA/PVC substrates was all caused by the failure of interface after 24 h.With increasing mole ratio of HDI/IPDI

the adhesive strength of adhesive to EVA/PVC substrate increased

and when the mole ratio of HDI/IPDI was 7∶1

the performance of WPU adhesive was the best.