Magnesium-Aluminium Layered Double Hydroxide By Liquid Coprecipitation Method And Its Flame Retardancy

Magnesium-Aluminium Layered Double Hydroxide(Mg-Al LDH)is a novel kind of inorganic flame retardant,which is no-halogen,non-toxic no-volatilization and higher stability.The aim of our study is to prepare Mg-Al LDH with good crystal property,complete crystal and uniform grain.In this dissertation,Mg-Al LDH is prepared by liquid coprecipitation method.The influence of ion concentration (including the concentration of OH^-,CO₃^2-and the whole reactant),reaction temperature and the drying time to the preparation of Mg-Al LDH are discussed systematically.Conclusions are as follows:â‘ The crystal shape of the Mg-Al LDH is hexagonal and the crystal size of Mg-Al LDH increase with the increasing of OH^- concentration.â‘¡The production ratio and the average size of Mg-Al LDH increase with the increasing of CO₃^2- concentration.â‘¢The output of Mg-Al LDH increase multiple while the whole reactant concentration increase,the average grains increase too.â‘£Mg-Al LDH can be prepared when reaction temperature higher than 60℃.⑤There are two stages of thermal decomposability of Mg-Al LDH.The first thermal decomposition is at about 230℃with the weight loss of 16%,which dues to the release of the four cyrstal water. The second happens at about 400℃with the weight loss of 28%as a result of the release of the carbon dioxide and the water decomposed from hydroxyl,MgO and Al₂O₃ remain at last.Mg-Al LDH is modified by KH550 which is a coupling agent,then added into soft polyurethane foam plastic to make the compound material.When the mass of coupling agent KH550 is 5%of the Mg-Al LDH,the modification is best.The LOI(limited oxygen index)increases with the amount of Mg-Al LDH,when Mg-Al LDH and ATH are added into soft polyurethane foam plastic at the same loading level,the former effect is better.Nylon 66 fibers dips into the original solution(Mg-Al LDH suspension after washing and filtration)for different time(12h and 24h),then drying at 100℃to make the compound of Mg-Al LDH/PA 66.Mg-Al LDH attachs to the fibers tightly,and the long the soakage time,the more the Mg-Al LDH attach to.The LOI increases with the soakage time. It indicates that Mg-Al LDH is a high performance and promising flame retardant.