Novel Synthesis And Nitrogen And Phosphorus Flame Retardant Epoxy Resin

In this paper, two flame retardants, poly [dimethylene diethylenetriamine hypophosphorous acid](FRA) and poly [dimethylene ethylenediamine hypophosphorous acid](FRB), were synthesized by condensation addition and electrophilic addition, using hypophosphorous acid as base, diethylenetriamine, ethylenediamine and formaldehyde as raw materials, hydrochloric acid as catalyst. The structures and properties of two flame retardants were determined by nuclear magnetic resonance (1H sNMR,13C sNMR) spectra, Fourier transform infrared (FTIR) spectra, elemental analysis, and thermo-gravimetric analysis (TGA). The synthetic conditions were investigated and optimized, such as reaction temperature, acidity, the proportion of raw materials, reaction time.Two flame retardants synthesized were applied to epoxy resin (EP) for flame-retardant composites (FRA/EP, FRB/EP). Flammability was investigated by horizontal and vertical burning test.When the amount of flame retardants increased, EP composites showed better flame retardancy. When the addition amount of FRA, FRB reached18%, EP composites exhibited good flame retardancy with FH-1grade and no dripping. The morphology and structures of carbon residues were studied by scanning electron microscopy (SEM) and FTIR. SEM figures showed that adding flame retardants to EP formed compact carbon layer when burning and had excellent fire retardant effect. TGA showed that the addition of FRA, FRB reduced initial degradation temperature and the rate of thermal degradation. The flame retardants had a great influence on mechanical properties, that is, tensile strength and flexural strength were reduced to a certain extent.This paper also studied the compounding effect of FRA, FRB with montmorillonite (OMMT), aluminum phenylphosphinate (ALPP), aluminum phosphinate (ALHP). EP composites showed better flame retardancy after adding OMMT, ALPP or ALHP. Thermal degradation rate of the composites decreased obviously after mixing. Initial decomposition temperature reduced and the char yield improved a lot. Mechanical properties of composites showed some improvement compared to FRA, FRB alone. Tensile strength increased by44.5%and flexural strength57.6%when using OMMT-FRA. Tensile strength of EP composites improved adding ALPP-FRA, ALPP-FRB mixtures. Compatibility between flame retardant and EP influenced the mechanical properties.