Photodegradation behavior of waterborne polyurethanes with different segment distributions and lengths

•Photodegradation mechanism for waterborne polyurethane is clarified.•The mechanism relies on the segment distribution and length.•The photodegradation behavior of the prepolymer polyurethane is strongly affected by the soft segment length.

Waterborne polyurethanes with different segment distributions and lengths were synthesized by one-shot and/or prepolymer processes. The photodegradations were performed with a rotary UV photochemical reactor in water, and the chain scission degrees were investigated with a Dynamic light scattering (DLS) measurement. The photodegraded polyurethane dispersions were molded into films by a solvent-casting method and were studied with various measurements in detail. The dispersion particle of the one-shot polyurethane had defects in the outside phase because of heterogeneous distribution of the hard segment (HS), and the inner soft segment (SS) was intensely photodegraded by the UV irradiation. On the other hand, the HS of prepolymer polyurethane was homogeneously distributed, and higher photodegradation stability was shown. The photodegradation behavior of the prepolymer polyurethane was strongly affected by the SS length.