Study On The Flame Retardance Of Glass Fiber Reinforeced Polyamide 6 And Polyamide 66 By Melamine Polyphosphate

In this paper, melamine polyphosphate (MPP), a kind of nitrogen-phosphourous composite flame retardant, was used for flame retarding glass fiber reinforced polyamide 66 (GFPA66) and polyamide 6 (GFPA6), and the affecting factors on the flame retardancy, mechanical performance and processability of the obtained materials were investigated. The flame retardant mechanism of different systems were also analysed, providing the experimental and theoretical basis for halogen-free flame retardence of polymer materials, giving a new method to solve the problems that the GFPA materials are difficult to flame retard because of the "candlewick effect" of glass fibers and the flame retardant GFPA materals can't poccess good mechanical performance. The obtained flame retardant GFPA materials can pass UL94 1.6mm V-0 rating and have good mechanical properties, showing excellent comprehensive performances and promising applications.MPP was prepared in an organic amine solvent from melamine and polyphosphorous acid (PHPO) through only one step, and the obtained MPP was used for the flame retardance of GFPA66 in the first section. The influences of synthesis condition such as reaction temperature, reaction time and adding fashion of PHPO solution on the flame retardancy and mechanical properties of the obtained flame retardant GFPA66 materials were investigated, and the optimized synthesis conditions were gained. The obtained MPP possesses excellent flame retardancy for GFPA66, achieving UL94 1.6mm V-0 rating with 25 wtï¼…of MPP and 30 wtï¼…of glass fibers, and the obtained materials exhibit pretty good mechanical properties, with tensile strength 120 MPa and notched impact strength 6.7 kJ/m~2. In addition, the flame retardant mechanism of the system was investigated through some characterizations (eg. thermal analysis).MPP was prepared through the heat treatment of melamine phosphate (MP) at high temperature, which was obtained through the reaction between melame and phosphrous acid in aqueous solution, and the obtained MPP was used for the flame retardance of GFPA6 in the second section. Our previous experiments found that using MPP alone, at a traditional loading range, can't endow the obtained GFPA6 materials with satisfying flame rtetardancy, but with the addition of acidic substance can help to improve the flame retardancy of materials. So we used the self-made solid acid together with MPP for the flame retardance of GFPA6 to improve the flame retardancy of GFPA6 materials. Because the compatibility of solid acid with PA6 matrix is poor and the direct contact between the two may cause the degredation reaction of PA6 while processing, resulting in the reduction of the mechanical performance of materials, we used a kind of macromolecular charring agent encapsulating on the solid acid to form composite synergist (TES), which was applied for flame retardant GFPA6 together with MPP. The introduction of macromolecular charring agent accelerates the charring process and changes the interfacial property between glass fibers and PA6, weakening the "candlewick effects" of glass fibers in PA6, beneficial for the flame retardancy. In addition, macromolecular charring agent encapsulating on the unstable solid acid improves the compatibility between the two and isolate solid acid from PA6 resin, preventing the chemical interaction between them. Serving as a synergist, solid acid played the role of a strong acid source, which could promote the System to form much more condensed and closed char layers. The influences of TES on the flame retaedancy, mechanical performance and processability of the obtained flame retardant GFPA6 materials were investigated. It was proved that this established technology provided an effective approach to prepare halogen-free flame retardant GFPA6 materials. With only 3 wtï¼…of TES can make the obtained materials achieve UL94 1.6 mm V-0 rating, the tensile strength, elongation at break, impact strength and bend strength are 104.2 MPa, 5.0ï¼…, 4.3 kJ/m~2 and 162.7 MPa, respectively, and the melt flow index is 23.7 g/10min, showing a good comprehensive performance and a promise in the future commercial application.