Poly(acrylated epoxidized soybean oil)-modified carbon nanotubes and their application in epoxidized soybean oil-based thermoset composites

Poly(acrylated epoxidized soybean oil) (PAESO) has been grafted on the surface of multiwalled carbon nanotubes (MWCNTs) by reversible addition–fragmentation chain-transfer reaction (RAFT). MWCNTs–PAESO as reinforcement has been successfully applied to prepare epoxidized soybean oil/maleopimaric-based thermosetting composites with good dispersion through probe ultrasonic treatment in ethyl acetate. Micromorphology analyses on composites by transmission electron microscopy and scanning electron microscopy show that MWCNTs–PAESO has better dispersion stability in both ethyl acetate and epoxy matrix and better interface bonding effect with cured matrix, resulting in more uniformly and separately dispersed behavior than hydroxylated multiwalled carbon nanotubes. Correspondingly, by the method of molecular dynamics simulation, it is verified that the nonbond energy and van der Waals force of CNTs–PAESO in solvent can be relatively reduced, and that CNTs–PAESO possesses higher binding energy with matrix compared with CNTs-OH. Therefore, MWCNTs–PAESO and PAESO have synergistic enhancement on the mechanical properties of composites demonstrated by rheology testing and dynamic mechanical analysis. The appropriate amount of MWCNTs–PAESO loading at 0.15 wt% can increase the glass transition temperature (T_g) of thermoset from 83.8 to 96.3°C, resulting in the improvement of both mechanical and thermal properties. These results show that surface-grafting MWCNTs with homologous polymer can effectively increase the interfacial compatibility between matrix and MWCNTs, thereby improving the thermal and mechanical properties of composites.