Study on Application of Magnesium-based Retardant Materials in Polyolefin Thermoplastic Elastomer
Supervisor:xue dong feng
The malignant fire in high-rise buildings and public places caused by polymer materials has a serious impact on social and public safety,which restricts the large-scale use of polymer materials in such buildings and places.Using flame retardant to improve the flame retardancy and smoke suppression of polymer materials is the effective method to solve this problem.Magnesium-based flame retardant are widely used because of their multiple flame retardancy,low smoke production,nontoxicity and non-secondary pollution.In this thesis,the flame retardant treatment of polyolefin thermoplastic elastomer(TPO)with magnesium-based flameresistant materials was studied,so that it has good flame retardancy,smoke suppression,safety performance and mechanical property.Conclusions are summarized as follows:(1)Magnesium hydroxide,magnesium sulfate and basic magnesium carbonate were synthesized by direct precipitation method.Magnesium sulfate,magnesium hydroxide and basic magnesium carbonate display nanosized whiskers,nanosheets and micro-particles respectively.The dispersion of magnesium hydroxide and basic magnesium carbonate in TPO was significantly better than that of anhydrous magnesium sulfate and basic magnesium sulfate.The carbonization effect of combustion residue of magnesium hydroxide-TPO and basic magnesium carbonate-TPO composites was obviously better than that of magnesium sulfate-TPO and basic magnesium sulfate-TPO composites,which indicating that the compatibility of magnesium-based compounds and TPO has effect on the carbonization effect of composites.(2)Effects of different kinds of magnesium-based compounds on the flame retardancy and smoke suppression of TPO composites were different.Magnesium hydroxide had the best flame retardancy and smoke suppression.The heat release rate peak,the total heat release in 600s?smoke production rate peak and total somke production in 600s of TPO composites with 35wt%magnesium hydroxide decreased by 31.4,35.6,50.0 and 56.0%compared with pure TPO.Magnesium hydroxide also had the most significant effect on reducing the fire risk of TPO composite.The mechanical property of TPO composites with a low addition ratio of magnesium hydroxide was not reduced obviously.(3)When the mass ratio of magnesium hydroxide to aluminum hydroxide was 4:1,it had the best effect on heat release suppression of TPO.The heat release rate peak and the total heat release in 400s of TPO composites with 35wt%compounded flame retardant decreased by 41.6 and 39.6%compared with pure TPO.Magnesium hydroxide used alone had better smoke suppression effect than combined with aluminum hydroxide.TPO composites with 35wt%magnesium hydroxide and magnesium hydroxide/aluminum respectively can reach the quasi-safety level 2(ZA2)of fire effluent toxicity.(4)The surface modification of magnesium hydroxide with rare earth coupling agent by dry process had obtained a good result.When the amount of magnesium hydroxide flame retardant was 35wt%,the flame retardancy and smoke suppression of modified magnesium hydroxide was better than that of magnesium hydroxide.When the amount of magnesium hydroxide was increased to 50wt%,the heat release rate peak of composites with unmodified magnesium hydroxide and modified magnesium hydroxide decreased by 57.1 and 55.6%respectively compared with pure TPO.The total heat release in 400s decreased by 69.2 and 65.60%,smoke production rate peak decreased by 77.3 and 77.3%,and the total somke production in 400s decreased by 91.0 and 87.4%respectively compared with pure TPO.The toxic classification of fire effluent for materials can be improved to quasi-safety level 1(ZA1).The flame retardancy and smoke suppression of magnesium hydroxide can not be further improved throuth surface modification with this additive ratio,but the surface modification of magnesium hydroxide can improve the mechanical property of TPO composites.