Synthesis of New S-Triazine Bishydrazino and Bishydrazido-Based Polymers and Their Application in Flame-Retardant Polypropylene Composites

In this study six new s-triazine bishydrazino and bishydrazido-based polymers were synthesized via condensation of bishydrazino s-triazine derivatives with terephthaldehyde or via nucleophilic substitution of dichloro-s-triazine derivatives with terephthalic acid hydrazide. The synthesized polymers were characterized by different techniques. The new polymers displayed good thermal behavior with great values in terms of limited oxygen indexed (LOI) 27.50%, 30.12% for polymers 5b,c (bishydrazino-s-triazine based polymers) and 27.23%, 29.86%, 30.85% for polymers 7a–c (bishydrazido-s-triazine based polymers) at 800 °C. Based on the LOI values, these polymers could be classified as flame retardant and self-extinguishing materials. The thermal results also revealed that the type of substituent groups on the triazine core has a considerable impact on their thermal behavior. Accordingly, the prepared polymers were mixed with ammonium polyphosphate (APP) in different proportions to form an intumescent flame-retardant (IFRs) system and were introduced into polypropylene (PP) to improve the flame-retardancy of the composites. The best results were obtained with a mass ratio of APP: 5a–c or 7a–c of 2:1, according to the vertical burning study (UL-94). In addition, the presence of 25% “weight ratio” of IFR in the composite showed great impact and passed UL-94 V-0 and V-1 tests.

Synthesis, Characterization of sym-2,4,6-trisubstituted-s-Triazine Derivatives and Their Effects on Flame Retardancy of Polypropylene Composites

Polypropylene (PP) is flammable material, which brings latent danger to the environment and human society. Therefore, developing new environmentally friendly and effective flame-retardant is one of the most important ways to improve the flame retardancy of PP and improve safety during its lifetime. Herein, we describe the synthesis of five sym-2,4,6-trisubstituted-s-triazine derivatives, namely, N2,N4,N6-triphenyl-1,3,5-triazine-2,4,6-triamine (TAT), N2,N4,N6-tris(4-bromophenyl)-1,3,5-triazine-2,4,6-triamine (TBAT), N2,N4,N6-tris(4-chlorophenyl)-1,3,5-triazine-2,4,6-triamine (TCAT), 4,4′,4″-((1,3,5-triazine-2,4,6-triyl) tris(azanediyl)) triphenol (THAT), and N2,N4,N6-tris(4-methoxyphenyl)-1,3,5-triazine-2,4,6-triamine (TMAT), from the reaction of cyanuric chloride and p-substituted aniline employing conventional heating or microwave irradiation. The prepared compounds characterized by different techniques, such as Fourier-transform infrared (FTIR), Ultra-Violet and Visible (UV-Vis), Nuclear Magnetic Resonance spectroscopy (1H-NMR and 13C-NMR), Thermogravimetric Analysis (TGA), and differential scanning calorimetry (DSC). The effect of substituent on the aniline moiety has great impact on its thermal stability, as observed from the TGA and DSC data. Based on the TGA and DSC results, three triazine derivatives TAT, TBAT, and TMAT were used as charring agents in the presence of different proportions of ammonium polyphosphate (APP) to form an intumescent flame-retardant (IFR) system, to improve the flame retardancy of PP. The flammability property of PP was investigated by a vertical burning test (UL94). The results of UL94 revealed that the TXAT/APP (IFR) system influence the PP and could improve the flame retardancy of PP. Best results were obtained with the mass ratio of APP and TXAT 2:1. When the IFR loading was 25 wt%, it displayed great influence and passed V-0 with TMAT, and V-1 with both TAT and TBAT in the UL94 test.