Hydrothermal preparation of 2CaO•5B<sub>2</sub>O<sub>3</sub>•5H<sub>2</sub>O nanomaterials and evaluation of their flame retardant properties by thermochemical strategies

Abstract

<p indent="0mm">Borate is a kind of green and environmental protective flame-retardant, which has been used in fiber, resin and wood and the like. To solve this bottleneck problem of prepared larger particles for borate flame-retardant which makes its poor flame retardant in the research and application, we prepared the calcium borate 2CaO•5B₂O₃•5H₂O nanoplate and micro/nanosheet under hydrothermal conditions by adjusting pH of solution and reaction temperature, which were characterized by the XRD, FTIR, TGA, FESEM and TEM. The flame retardant properties of the prepared 2CaO•5B₂O₃•5H₂O samples were investigated by using multiple thermochemical strategies (including TGA, DSC and non-isothermal decomposition kinetics), and further verified by limited oxygen index method. The nanoplate sample has the less TG mass loss and heat release for DSC, as well as the bigger LOI value, and apparent activation energy <italic>E</italic>_a. These show that the flame retardant property of prepared 2CaO•5B₂O₃•5H₂O nanoplate sample is stronger than that of micro/nanosheet sample. The possible flame retarding mechanism has been proposed. In addition, the horizontal comparison shows that the flame retardant property of prepared 2CaO•5B₂O₃•5H₂O nanoplate is also better than that of 2CaO•B₂O₃•H₂O nanosheet. This research indicated that 2CaO•5B₂O₃•5H₂O nanoplate could be a potential utility-type flame retardant.