Structural Design of Colorless Transparent Polyurethane with Intrinsic UV Resistance and High Mechanical Performance for Protective Coating

ABSTRACT Polyurethane (PU) is widely used in production and daily life due to its excellent mechanical properties and strong plasticity. Long‐term ultraviolet (UV) irradiation will cause PU aging and shorten its service life. However, preparing UV‐resistant PU, which is colorless, transparent, and non‐migratory, remains a challenge. This work introduced the reactive benzotriazole UV absorber (R455) into the PU molecular chain to prepare colorless and transparent intrinsic UV‐resistant samples (PCU) by polymerization, using polycarbonate diol as soft segment, dicyclohexylmethane diisocyanate as hard segment, and 1,6‐hexanediol as chain extender. The results show that the light transmittance of the UV‐resistant PCU sample is about 90% in the visible light range. Moreover, the UV‐resistant PCU shows excellent mechanical properties with elongation at break respectively higher than 580% and tensile strength transcending 50 MPa. After UV irradiation for 192 h, the tensile strength as well as the elongation at break of the PCU sample without R455 of the original values are respectively reduced to simply 60.8% and 62.7%. Whereas the introduction of R455 gives the PCU sample excellent UV resistance, the PCU sample with 1.5% R455 is respectively about 99.0% and 92.8%. These samples can be used in various fields with both UV resistance and optical requirements.