微胶囊Mg (OH)2的合成及其对乙烯-乙酸乙烯酯共聚物的阻燃作用

用原位聚合方法合成了以微米Mg（OH）₂粒子为芯材、交联聚脲为壁材的微胶囊Mg（OH）₂（M-Mg（OH）₂）阻燃剂，并把M-Mg（OH）₂加入到乙烯-乙酸乙烯酯共聚物（EVA）中，研究了M-Mg（OH）₂对EVA的阻燃作用。采用FTIR、SEM、热分析和酸滴定方法研究了M-Mg（OH）₂的性质，用极限氧指数（LOI）和垂直燃烧方法（UL-94）研究了M-Mg（OH）₂/EVA复合材料的阻燃性能以及酸腐蚀对M-Mg（OH）₂/EVA复合材料阻燃性能的影响。结果表明，采用原位聚合方法能够成功地在Mg（OH）₂粒子表面包覆交联聚脲壁材，得到M-Mg（OH）₂。与纯Mg（OH）₂相比，M-Mg（OH）₂的颗粒尺寸增大，热稳定性增加，在水中溶解度显著降低，在EVA基体中分散更加均匀。阻燃剂用量相同时，M-Mg（OH）₂/EVA复合材料的LOI总是比Mg（OH）₂/EVA复合材料的数值稍大。阻燃剂与EVA质量比小于135∶100时，两种复合材料的垂直燃烧级别均为V-2级，阻燃剂与EVA质量比在135∶100~150∶100之间时，前者的燃烧级别为V-0级，而后者只能达到V-2级，阻燃剂与EVA质量比超过150∶100时，两种复合材料都能达到V-0级。M-Mg（OH）₂/EVA复合材料的耐酸性比Mg（OH）₂/EVA大幅度提高，可以在酸性环境中使用。

Synthesis of microencapsulated Mg(OH)2 and its flame retardant effect on ethylene-vinyl acetate copolymer

Microencapsulated Mg(OH)₂ (M-Mg(OH)₂) flame retardant with micro-sized Mg(OH)₂ particles as the core and cross-linking polyurea as the shell, was synthesized by in-situ polymerization. The obtained M-Mg(OH)₂ was incorporated into ethylene-vinyl acetate copolymer (EVA) and its flame retardant effect on EVA was studied. FTIR, SEM, thermal analysis and acid titration were used to investigate the properties of M-Mg(OH)₂. Limiting oxygen index (LOI) and vertical burning test (UL-94 VBT) were employed to study the flame retardancy of M-Mg(OH)₂/EVA composite and the effect of acid erosion on the flame retardancy of M-Mg(OH)₂/EVA composite. It shows that the surface of Mg(OH)₂ particles can be successfully encapsulated with cross-linking polyurea by in-situ polymerization and microencapsulated Mg(OH)₂ can be obtained. Compared with the pure Mg(OH)₂, the size of M-Mg(OH)₂ is larger, its thermal stability increases and the water solubility of M-Mg(OH)₂ decreases remarkably. The dispersion of M-Mg(OH)₂ in EVA matrix is more even than that of the pure Mg(OH)₂. The LOI of the M-Mg(OH)₂/EVA composite is always slightly larger than that of its Mg(OH)₂/EVA counterpart at identical loadings of flame retardant (FR). When the mass ratio of FR/EVA is less than 135:100, the VBT ratings of both composites are V-2. When the mass ratio of FR/EVA is between 135:100-150:100, the rating of the former is V-0, but the latter can only reach V-2 rating. When the mass ratio of FR/EVA surpasses 150:100, both composites can reach V-0 rating. In contrast with Mg(OH)₂/EVA composite, the acid resistance of the M-Mg(OH)₂/EVA composite increases substantially and it can be used in acid environment.