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    LI Yinghao, WANG Xinling. Synthesis and Properties of Functional Polyurethane-Acrylates Bearing Hindered Urea Bonds[J]. Journal of Functional Polymers, 2022, 35(5): 468-475. doi: 10.14133/j.cnki.1008-9357.20211228001
    Citation: LI Yinghao, WANG Xinling. Synthesis and Properties of Functional Polyurethane-Acrylates Bearing Hindered Urea Bonds[J]. Journal of Functional Polymers, 2022, 35(5): 468-475. doi: 10.14133/j.cnki.1008-9357.20211228001

    Synthesis and Properties of Functional Polyurethane-Acrylates Bearing Hindered Urea Bonds

    • Inspired by the dynamic properties of hindered urea bonds (HUBs), prepolymer of polyurethane-acrylate (PUA) with HUBs was designed and synthesized using 1,3-bis(2-isocyanato-2-propyl)benzene (TMXDI) as hard segment, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (TMPCA) as soft segment, isobornyl methacrylate (IBOMA) as reactive diluent, and 2-hydroxyethyl methacrylate (HEMA) as block agent. The prepolymer was subsequently UV-cured to obtain PUA photopolymer. The property and reaction mechanism of the incorporated dynamic HUBs were investigated via Differential Scanning Microcalorimetry (MicroDSC) and Fourier Transform Infrared (FT-IR) spectroscopy. And studies were carried out in terms of the repairability, shape memory and reshapability of the corresponding photopolymer. Results showed that the thermal effect of the HUB could be identified in MicroDSC analysis, as an endothermic peak appeared in the range of 46 ℃ to 56 ℃. In addition, the dynamic content variation of the isocyanate group (NCO) could be observed via temperature-dependent FT-IR in both prepolymer and cured resins. In the in-situ FT-IR spectra of prepolymer with HUBs, the characteristic peak of NCO was observed to increase when heated from 30 ℃ to 80 ℃, which later decreased when cooled down to 30 ℃. Also, the peak area of NCO characteristic peak increased in cured resins with increased temperature. The dynamic nature of HUBs allowed the obtained photopolymer to be repaired with a demonstrated improvement in mechanical properties. By drilling a 1 mm hole in the center of a testing sample, refilling prepolymer, and treating with UV-cure and post-cure, the tensile strength of the material was observed to recover from 13.8 MPa to 18.4 MPa after repairing. The incorporated HUBs provided the PUA resin with shape memory and reshaping capacities, and the testing sample was able to reserve a 45 MPa flexural strength after being reshaped.
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