Cure behavior and enhanced thermal properties of benzoxazine thermosets with isocyanate-terminated hyperbranched polyurethane of different degree of branching

Abstract In the study, we investigated the influence of degree of branching (DB) of isocyanate-functionalized hyperbranched polyurethanes (HPU –NCOX ) on the cure and thermal property of phenol-terminated benzoxazine oligomer (BZ –OH ). The structure of the as-synthesized HPU –NCOX was confirmed by proton nuclear magnetic resonance ( 1 H NMR and 13 C NMR), gel permeation chromatography (GPC) and Fourier transform infrared spectra (FT-IR). Thermally activated cross-linking behavior as well as the thermal stability of HPU –NCOX /BZ –OH blend was investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). HPU –NCOX can covalently incorporate into BZ –OH via urethane reaction. Both the cure kinetics and the weight residue of HPU –NCOX /BZ –OH copolymer reveal a gradual increase with the improvement of DB of HPU –NCOX . Graphical abstract A novel isocyanate-functionalized hyperbranched polyurethanes (HPU –NCOX ) with degree of branching (DB) ranging from 25.1 to 51.1 % were successfully synthesized. The HPU –NCOX and benzoxazine copolymers exhibit enhanced cure kinetics with the increase of DB of HPU –NCOX .