Synthesis and properties of thermosetting resin based on urushiol

We have synthesized a novel benzoxazine monomer and polybenzoxazine thermosetting resin based on urushiol, a natural product. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies demonstrate that the thermally activated ring opening polymerization of the benzoxazine occurs at around 210 degrees C without addition of catalyst. Thermal gravimetric analysis (TGA) measurements show the temperatures corresponding to 5% and 10% weight loss are 325 degrees C and 357 degrees C, respectively, with a char yield of 22% at 600 degrees C. Dynamic mechanical analysis (DMA) studies indicate the urushiol-based polybenzoxazine exhibits excellent toughness with a storage modulus (G') of 606 MPa at room temperature and an elongation at break of 17.4%.