Enhancing the Thermal Stability and Flame Retardancy of Transparent Fire-Retardant Coatings Applied on Wood Substrates by Introducing Multi-walled Carbon Nanotubes
Multi-walled carbon nanotubes (CNTs) were introduced into the structure of phosphate ester (PEA) to prepare a series of novel flame retardants named PEA-functionalized CNTs (CPEAs). The chemical structures of CPEAs were carefully characterized by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (1H NMR) spectroscopy. Then, the obtained PEA and CPEAs were mixed with amino resin to produce five kinds of fire-retardant coatings applied on plywood boards. The optical transparency, fire protection performance, and thermal behavior of the transparent coatings were investigated by various analytical methods. The optical transparency analysis shows that the transparency value of coatings gradually decreases with increasing CNTs contents, and a small amount of CNTs imparts a high degree of transparency to the resulting coatings. The results from the flammability tests indicate that the CPEAs impart lower weight loss, char index, flame spread rating, heat release rate, and total heat release to the resulting coatings than those of PEA. The thermo-gravimetric analysis reveals that the CPEAs possess higher thermal stability and residual weight to the resulting coatings compared to PEA. Char residue analysis indicates that the introduction of CNTs is beneficial to generate more P–N–C and P–O–C cross-linked structures in the condensed phase that form a high-quality intumescent char against heat and mass transfer, thus effectively improving the flame retardancy and thermal stability of the transparent coatings.
KeywordsCarbon nanotubes Transparent fire-retardant coating Fire protection performance Thermal behavior
This work was supported by the National Natural Science Foundation of China (No. 51676210), the Hunan Provincial Natural Science Foundation of China (No. 2018JJ3668), and the National Key R&D Program of China (No. 2017YFB1201204).
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