Studies on the effects of different multiwalled carbon nanotube functionalization techniques on the properties of bio-based hybrid non-isocyanate polyurethane

Abstract

A novel synthesis method for multiwalled carbon nanotube (MWCNT) modified bio-based hybrid non-isocyanate polyurethane (HNIPU) is proposed in this paper. Modification methods for several properties of MWCNTs–HNIPU were systematically studied. MWCNTs were grafted with carboxyl and amino groups using a condensation reflux device. Au nanoparticles were synthesized on the surface of the MWCNTs via a reduction reaction and Fe₃O₄ particles were decorated on the MWCNTs using a hydrothermal method. FTIR, TEM, XRD, XPS and Raman techniques were employed to confirm the compositions and structures. Then, five different types of MWCNT were utilized for blending with non-isocyanate polyurethane (NIPU) via solution methods. After curing with epoxy resin E-51, the cross-linked composites were applied as coatings. A series of tests demonstrated that HNIPU composited with MWCNTs–COOH–Au had the highest T_g value, the best thermal, thermodynamic and mechanical properties, and excellent pencil hardness, adhesion, flexibility and impact strength, while HNIPU composited with MWCNTs–COOH–NH₂ had the best water absorption and swelling properties. These results showed that the properties of hybrid non-isocyanate polyurethane can be adjusted via different MWCNT surface modification approaches or the addition of nanoparticles, so this kind of polyurethane has a vast development space for coating applications.