Synthesis, characterization and fire retardancy of titania-based materials coated on wood

Abstract

The number of fire cases in Malaysia has recently been increasing year after year, necessitating fire prevention measures. One prevention method is introducing fire retardant (FR) coating materials. FR coating material is a coating layer that works to prevent and reduce the probability of the material being flammable. Titania (TiO2) nanoparticles (NPs) and silica/titania (SiO2/TiO2) nanocomposites (NCs) worked as the FRs coating materials in this project, while rubberwood functioned as the flammable substrate material. The fire performance behaviour was then investigated using cone calorimeter, thermogravimetric analyzer (TGA), and flammability tests. According to the findings, FR coating of TiO2 NPs and SiO2/TiO2 (ratio of 0.1:1) NCs were able to increase the decomposition temperature (OD) of rubberwood by 41.32°C and 37.59°C, spontaneous ignition (SI) by 45.95°C and 32.6°C, and delayed ignition time (IT) by 79 s and 114 s. The results also proved the reduction in the intensity of fire (FI), heat release rate (HRR) by 43.32 kW/m2 and 45.87 kW/m2, rate of combustion (ROC) by 0.144 mm/s and 0.142 mm/s, mass loss rate (MLR) by 2.7 g/s and 2.9 g/s, and combustion efficiency (EHC) by 4.89 mJ/kg and 4.95 mJ/kg, respectively. The fuzzy logic system determined from these parameters that the HRR parameter should be considered as the key parameter that needs to be decreased in order to improve the FR performance of the TiO2-based materials. The physicochemical properties of TiO2-based materials coated on wood were then analyzed by various instruments and methods. Field emission scanning electron microscopy (FESEM) showed that the TiO2-based materials coated on the wood are spherical in shape, in the nano-range (25 to 40 nm), and agglomerated on the surface of the rubberwood. Meanwhile, energy dispersive X-ray (EDX) confirmed that the presence of titanium (Ti) and silica (Si) as the primary elements. The principal functional groups of TiO2 and SiO2 were also visible by fourier transform infrared (FTIR) spectroscopy. The X-ray diffraction patterns (XRD) demonstrated that the TiO2 in both TiO2 and SiO2/TiO2 samples are present in the anatase phase with a lower crystallinity, corresponding to the bandgap energies (3.2 eV and 3.4 eV) determined using diffuse reflectance ultraviolet-visible spectroscopy (UV-Vis). Through the peel adhesion test, it was proven that the application of 3-aminopropyltrimethoxysilane (APTMS) as a surface modifying agent allowed strong adhesion between the TiO2-based materials and wood and was uniformly coated. The wettability test showed that the surface of the rubberwood changed from superhydrophilic to hydrophilic. In conclusion, this study has demonstrated that TiO2 and SiO2/TiO2 (0.1:1) are the best coating materials on wood that can successfully operate as fire retardant materials, displaying the potential to decrease the performance of wood burning.