Research And Application Of Environment-friendly Flame Retardants Based On Layered Double Hydroxides

Recently, the enviornmental friendly flame retardants and technology have attractedmore attention. As one of the typical inorganic layered anionic materials, the hydrotalcite（LDH） and hydrotalcite-hike compounds （HTLcs） have been applied widly and show abright prospect, due to their multiple functions such as adsorption, flame retarding, smokesuppression and filling. The hydrotalcites were modified in this thesis to improve thecompatibility between hydrotalcite and polymer materials as well as the flame retardingproperties.1. Synthesis of intercalated LDHs. The LDHs were intercalated by usingmelamine-formaldehyde resin （LDHs-1）, phosphate monoester PVA （LDHs-2）, boratemelamine （LDHs-3） and sodium ethylene diamine tetramethylene phosphonate （LDHs-4）,respectivly. The modified LDHs have been charactered by XRD, FT-IR, SEM-EDS andTG-DTA. Orthogonal experiment and univariate analysis were introduced to optimize thesynthetic conditions. Results show that the optimal conditions for synthesis of LDHs-2arethat the phosphate monoester PVA-to-LDH mole ratio is about1:2, the reaction time isabout2h and the reaction temperature is about90℃.2. Performance of modified LDHs/epoxide resin composites. The flame retardancyand mechanical properties of LDHs/epoxide resin composites were tested by oxygen index（OI） method and tensile test. Results show that the flame retardancy and mechanicalproperties of LDHs/epoxide resin composites are enhanced by modified LDHs. The OI ofthe composites increases with the concentration of modified LDHs increasing. As thedosage of modified LDHs reaches20%, the optimal mechanical properties of thecomposite is obtained. The OI and mechanical properties are higher than that ofcommercial LDHs.3. Synthesis and application of melamine-formaldehyde resin modified magnesiaFGD residue （MR）. As the content of MMR reaches20%, the OI of composites reaches24%. As the concentration of modified MR （MMR）/APP reaches20%（m（MMR）:m（APP）=1:1）, the OI of MMR/APP/EP reaches34%. As the concentration ofMMR/MP reaches20%（m（MMR）:m（MP）=1:1）, the OI of MMR/MP/EP reaches29%. Theremarkable synergistic effects of MMR-ammonium polyphosphate （APP）（or phosphoricacid melamine, MP） are observed. This is attributed to the enhanced dehydrogenationreaction by APP（MP） and the crosslinking carbon skeleton combining with the catalyzing by MgO and SiO₂in the MMR. Furthermore, the nonflammable gases from thedecomposition of APP（MP） and Mg（OH）₂also play a key role in the flame retardingprocess. To sum up, The flame-retardant and mechanical properties of EP were improvedby the MMR. This can be attributed to the excel flame retarding properties of modifiedMMR and the coordinating compatibility between MMR and EP.