The Synthesis And Application Of Nitrogen-containing Flame-retardant Resin With Different Structures

The halogen-containing flame retardants have been widely used for a long time in electrical and electronic fields because of its excellent flame retardant effect. However, researchers have reported that the halogen-containing flame retardants could release toxic gases at high temperature, which has limited its application. In recent years, the technology of halogen-free and phosphorus-free flame retardant has become the one of the most active research areas. In these active research yields, nitrogen flame retardant is a fast-growing research field and received extant attentions.In this paper, three kinds of nitrogen-containing phenolic resin with different structures were synthesized. The phenol, melamine and formaldehyde were choosed as raw materials and the ratio of nitrogen phenolic resin were optimized. The structural characteristics of nitrogen-containing phenolic resin were investigated by FTIR. The effects of different ratio, acid value and catalyst on the structure of the reaction products were discussed. The results indicate that the phenolic resin with nitrogen located at para position achieved the highest contant when the ratio of phenol: formaldehyde: melamine is 5:7:2, the catalyst is ammonia, reaction temperature is 85 90℃and pH value is about 8; the ortho position nitrogen-containing phenolic resin achieves the highest yeild when the ratio of phenol: formaldehyde: melamine is 10:8:2, the catalyst is MgO, reaction temperature is 95 100℃, pH value is about 6, At last, the metla position nitrogen-containing phenolic resin will achieve the highest yeild when the ratio of phenol: formaldehyde: melamine is10:10:3, the catalyst is Mg(OH)₂, reaction temperature is 105～110℃. pH value is about 10.The structures of nitrogen-containing phenolic resin and its composites have been characterized by fourier transform infrared spectroscopy (FTIR), thermo gravimetric analyzer (TGA) and differential scanning calorimetry (DSC). FITR analysis indicates the structures of three nitrogen-containing phenolic resins meet the expected requirements. TGA analysis indicates that temperature resistant index of compoud nitrogen-containing phenolic resin is 172℃. Moreover, the laminating process was determined according to the DSC data and the phenolic/epoxy laminates reinforced with glass cloth were prepared. The properties of this laminates such as flame retardancy, mechanical and electrical properties were also examined. Results showed that the laminate had a very good comprehensive performance. The LOI value is 33.5%, the burning time after the first time away from the fire is 5.1s, the burning time after second time away from the fire is 5.6s, reaches a UL94V-0 level. The layer-oriented breakdown voltage is 47.4kV, normal surface resistance is 5.33×10¹³Ω, surface resistance after immersion in water is 7.37×10¹¹Ω, adhesion strength is 7.564KN, and the bending strength is 425Mpa.