Synthesis and characterization of new hybrid hexasubstituted cyclotriphosphazene-schiff bases and its effect on the fire retardancy of epoxy resin composite

• Main Author: Nur Atika Waldin
• Format: Thesis
• Language: English; English
• Published: 2023
• Subjects: TH1000-1725 Systems of building construction Including fireproof construction, concrete construction
• Online Access: https://eprints.ums.edu.my/id/eprint/41214/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/41214/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/41214/
• Institution: Universiti Malaysia Sabah

Broad research in hexasubstituted cyclotriphosphazene derivatives has become a great investment especially in science and technology. Cyclotriphoshazene poses high thermal properties and self-extinguish ability, making it a valuable additive as fire-retardant. A series of new fire-retardant compounds based hexasubstituted cyclotriphosphazene with Schiff bases linkage was successfully synthesized. These compounds, labelled 4a-e, having different alkyl length terminal end (pentyl, nonyl, decyl, dodecyl and tetradecyl) through nucleophilic substitution. All synthesized compounds were obtained in high percentage yield within the range of 81.45% - 95.68%. The structures of these compounds were characterized using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and CHN elemental analysis revealed a well fitted data compared to each compound structure and showed high purity. To have better insight on their fire-retardant and mechanical behaviour, epoxy resin (EP) was used as polymer matrix. The thermal stability of the compounds was evaluated using thermogravimetric analysis (TGA). The char yield percentage at 600°C was increased gradually as the alkyl chain length at the end terminal of the compound increased. The incorporation of fire-retardant additives, 2a-e, 3, and 4a-e significantly increased the limiting oxygen index (LOI) compared to pure EP, which exhibited a LOI value of 22.75%. Compound 4e attached to tetradecyl terminal alkyl group gave the highest LOI value of 26.71%. The surface morphology of char residues from the LOI test was analyzed using field emission scanning electron microscopy (FESEM) showed a good improvement on a compact char residue formed as physical barrier to the matrix which decelerate the heat transfer. Moreover, the mechanical property of synthesized compounds was also investigated. The effect of fire-retardant compounds of hexasubstituted cyclotriphosphazene, 4a-e to epoxy resin proved an increased mechanical property compared to pure EP with tensile strength of 8.06 MPa. The incorporation of compound 4a to EP showed the highest tensile strength with 24.61 MPa followed by 4e with 21.48 MPa. This study concluded that it is essential to maintain both the mechanical properties and fire retardancy of polymers in order to achieve satisfactory safety and high functionality.