协效剂对聚丙烯/氢氧化镁复合材料阻燃和力学性能的影响

采用硬脂酸钠改性后的氢氧化镁与聚丙烯（PP）材料熔融共混，分别以二氧化硅或硼酸锌或聚磷酸铵与季戊四醇的混合物为协效剂，制备氢氧化镁填充量为50%（质量分数）的阻燃聚丙烯。考察了聚丙烯复合材料的燃烧性能、拉伸强度、冲击强度和断面形貌。结果表明：5%（质量分数）的硬脂酸钠改性氢氧化镁填充聚丙烯制备的复合材料拉伸强度、冲击强度和分散性都高于未改性聚丙烯/氢氧化镁复合材料；当协效剂添加量不超过3%时，二氧化硅或硼酸锌对复合材料有协同阻燃和填充增强的作用；聚磷酸铵和季戊四醇的混合物与氢氧化镁有较好的协同阻燃作用，且随着用量的增加，复合材料拉伸强度下降，冲击强度变化不大。

Effects of synergists on the flame retardancy and mechanical properties of polypropylene/Mg(OH)2 composites

Magnesium hydroxide modified by 5% sodium stearate has been doped in polypropylene(PP) with a filling level of 50%,with silicon dioxide,zinc borate or a composite flame retardant system consisting of ammonium polyphosphate and pentaerythritol as synergists.The properties and structure of the resulting composites were characterized by limiting oxygen index(LOI),tensile strength,and impact strength measurements and scanning electron spectroscopy images of transects.The results show that the tensile strength and impact strength of the modified PP/Mg(OH)2 composites were higher than for the unmodified sample.The dispersity in PP of modified Mg(OH)2 was also enhanced compared to the unmodified sample.Silicon dioxide and zinc borate showed synergistic flame retardant and fill reinforcing effects,as their content was increased up to 3%.Addition of the composite flame retardant system consisting of ammonium polyphosphate and pentaerythritol afforded a good enhancement in flame-retarding properties.With increasing substitution of Mg(OH)2 by the composite flame retardant system,the tensile strength of the resulting composites were reduced,whilst the impact strength only varied slightly.