Abstract
A novel in-situ formation of bio-based coordination polyurethane (CPUs) have been demonstrated which could substitute to traditional petroleum-built PUs and was formulated by considering the objectives of green and sustainable development. Present work seeks to synthesize cheap and environment-friendly M(II) [Mn(II), Co(II), Ni(II) and Zn(II)] coordinated PUs [M(II)ColF-AliPU] using cardanol formaldehyde (ColF) and aliphatic diisocyanate. The ambient-cured free-standing film/coatings were developed and their properties were discussed and compared. However, free-standing films of Ni(II)-ColF-AliPU and Zn(II)-ColF-AliPU were not obtained even after subjecting the curing at elevated temperatures. FTIR and UV–Visible analysis helps in confirming the octahedral [Mn(II), Co(II), Ni(II)] and tetrahedral [Zn(II)] coordinated structures. The incorporation of metal ions was confirmed by EDX analysis, and the semi-crystalline behavior observed (XRD) was collaborated to the presence of hexamethylene chains of HMDI with nanostructured framework (spheres and tubes). Metal incorporation increases the thermal stability of M(II)-ColF-AliPU and accredits the applications up to 200–220 °C. Co(II) showed the best thermal stability and flame retardancy among other PUs, however, these films were found to be comparatively less thermally stable than aromatic diisocyanate (TDI) based CPUs. After metal integration, the physicomechanical study indicated significant mechanical strength in terms of scratch resistance (1.8 kg), high impact (1.50 × 102 lb./in.), excellent adhesion, bending (1/8 in.), and improved gloss value, although less than M(II)-ColF-ArPU (CPU with aromatic diisocyanate). Water contact angle of ColF-AliPU (151°), Mn(II)-ColF-AliPU and Co(II)-ColF-AliPU (152° and 153°, respectively) revealed the development of superhydrophobic surfaces. The antibacterial activity results revealed Co(II)-ColF-AliPU to be the best composition for inhibiting the bacterial growth (E. coli, S. aureus, K. pneumoniae, and B. subtilis) and thus can be employed in market as antibacterial thin films and coatings.
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•In-situ synthesis of bio-based coordination polyurethanes•Synthesized from ColF, HMDI and 3d metal ions [Mn(II), Co(II), Ni(II) and Zn(II)]•Transparent film/coatings are chemically-mechanically robust, and thermally stable.•Film/coatings shows antibacterial and hydrophobic behavior.•FTIR and UV–Visible analysis confirming the octahedral and tetrahedral structures