Flame retardant mechanism of Mg(OH)2/polystyrene composites
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摘要: 把Mg(OH)2 (Magnesium hydroxide, MH) 在不同温度热处理不同时间, 得到一系列不同热分解状态的Mg(OH)2 (Treated magnesium hydroxide, t-MH)。以MH和t-MH为无卤阻燃剂, 聚苯乙烯(PS)为基体, 采用熔体共混法制备了MH/PS和t-MH/PS复合材料。详细研究了MH热处理对t-MH/PS复合材料燃烧性能的影响, 并以此实验结果为基础提出了复合材料的阻燃机制模型。结果表明, 随着热处理温度升高、热处理时间延长, MH逐渐分解并转化成MgO。在相同条件下t-MH/PS复合材料的阻燃性能较MH/PS复合材料显著降低, 但是仍然比纯PS有明显提高。此外, MH热分解产生的MgO有促进PS成炭的作用。MH/PS复合材料的阻燃机制是以下几种因素协同作用的结果: (1)MH分解吸热的冷却降温作用;(2)MH热分解释放水蒸气的气相稀释作用;(3)MH热分解产物MgO的固相阻隔与防护作用;(4)MgO促进PS成炭阻燃作用。Abstract: A series of Mg(OH)2 with different degradation states (t-MH) were obtained by pyrolyzing Mg(OH)2 (Magnesium hydroxide, MH) at various temperatures for different time. MH/PS and t-MH/PS composites were prepared by melt-compounding MH and t-MH as halogen-free flame retardants and PS as matrix. The influence of thermal treatment of MH on combustion behavior of t-MH/PS composites was investigated in detail. Based on the experimental results, a model of the flame retardant mechanism of MH/PS composites was proposed. It is indicated that MH gradually decomposes and changes into MgO with the rise of thermal treatment temperature and the elongation of thermal treatment time. Under identical conditions, the flame retardancy of t-MH/PS composite decreases noticeably than that of its MH/PS counterpart, but it is still much better than that of pure PS. In addition, the MgO produced by decomposition of MH can promote charring of PS. It is believed that the flame retardant mechanism of MH/PS composites derives from the synergistic effect of the following factors: (1) the cooling effect from endothermal degradation of MH; (2) the gas phase diluting effect of water vapor from degradation of MH; (3) the solid phase obstructing and shielding effect of MgO from degradation of MH; (4) the fire-proof effect from charring of PS induced by MgO.
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Key words:
- magnesium hydroxide /
- polystyrene /
- composite /
- combustion behavior /
- flame retardant mechanism
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