Effect of the hard segment on the properties of UV curable waterborne blocked polyurethanes

Two types of UV curable waterborne blocked polyurethanes (PUs) were obtained from 2,4-tolylene diisocyanate(TDI) and isophorone diisocyanate (IPDI), which had the same soft segments and different hard segments. The PUs contained both the UV curable C=C bond and the blocked NCO groups which could be de-blocked when heated. Effect of the hard segment on the properties of the two types of PUs was investigated. The FTIR spectra method was employed to confirm the structure of the PUs. The photo-DSC was used to study the photo-polymerization rate of the PUs under UV irradiation in the presence of a photo-initiator and the C=C conversion behaviors. Heating-up IR analysis was used to track the de-blocking process and the heat curing process. The thermal degradation analysis (TGA) was employed to investigate the thermal stability of the UV cured films before and after heat curing process. Dynamic mechanical properties of the UV and heat cured films were investigated by the dynamic mechanical thermal analysis (DMTA).