Synthesis of boehmite and its effect on flame retardancy of epoxy resin

In the present work, a facile and environmentally friendly method was presented to synthesize nano-boehmite (AlOOH) that was added in bisphenol A epoxy resin to improve the flame retardancy of the resin. The crystalline phase of the as-synthesized AlOOH was examined using X-ray diffraction measurements, while no peaks from the other phase are observed in patterns, and the sharp peaks demonstrate the high crystallinity of AlOOH. Scanning electron microscopy was used to observe the morphology of AlOOH; the results indicate that the thickness of the as-synthesized AlOOH nanosheets is about 23 nm. The thermogravimetric analysis of neat epoxy resin and AlOOH/epoxy nanocomposites with different contents of AlOOH (2.3%, 4.7%, 5.6%, and 10.2%, respectively) shows that the decomposition temperature of AlOOH/epoxy nanocomposites increases compared with the neat epoxy; a significant improvement in mass loss rate is observed when the content of AlOOH reaches 10.2%. The glass transition temperatures (T_gs) of nanocomposites were measured by differential scanning calorimetry; the results indicate that when the content of AlOOH in epoxy resins increases to 10.2%, the T_gs of AlOOH/epoxy nanocomposites can increase from 165.2°C to 181.4°C. Oxygen index test was used to investigate the flame retardancy properties of AlOOH/epoxy nanocomposites; the results obtained from these measurements further reflect the facts that AlOOH can improve the flame retardancy and T_g of epoxy resin.