Monofunctional benzoxazine from cardanol for bio-composite applications

In this study, a monofunctional benzoxazine monomer was synthesized by condensation reaction of aniline and formaldehyde with cardanol, a by product of cashew nut shell liquid (CNSL). The monomer was characterized by FTIR and 1H NMR spectral analysis. Curing characteristics were studied by differential scanning calorimeter. The exothermic peak associated with curing was observed from 230 °C to 291 °C with a peak maximum of 272 °C. Adding a small percentage of cardanol as phenolic initiator reduced the onset of cure as well as peak maximum temperature due to accelerated curing. Thermo gravimetric analysis indicated a peak decomposition temperature of 432 °C and a char yield of 24% at 800 °C. The viscoelastic properties of the neat cardanol benzoxazine, its jute fiber composite and the acrylonitrile modified jute fiber composites were studied with dynamic mechanical thermal analyzer (DMTA). The storage modulus (E′) value increased with fiber loading and showed a higher value for treated composite indicating an increase in interaction between fiber and resin matrix. On the other hand, the tan δ which is associated with glass transition, shifted to lower value compared to neat resin with incorporation of jute fibers.