Halogen-free flame-retardant compounds based on silane-crosslinked PP and EVA were prepared through a two-step melt blending method using magnesium hydroxide (MH) as a flame retardant,and the crosslinking efficiency of silane grafted onto EVA/PP compounds were investigated in terms of block-copolymerized PP (PP-B) and homo-PP(PP-H).The mechanical properties,hot elongation performance and flame-retardant properties of compounds were investigated by using universal testing machine,hot-set elongateion tester,limiting oxygen index and vertical burning experiments.The results indicated that the silane-crosslinked EVA/PP-B compounds achieved a higher crosslinking degree than the EVA/PP-H ones.The EVA/PP-B crosslinked compound could reach the crosslinking level required when the content of MH was lower than 120 phr.With increasing the MH content from 80 to 160 phr,the limiting oxygen index values of compounds increased from 25.0 to 32.2 vol ％,which were improved by 0.5 ％～1.5 ％compared to the un-crosslinked ones.The flame retardancy of compounds was improved up to the V-0 grade of GB/T 2408-2008 when the MH content exceeded 120 phr.The compounds were found to undergo a two-stage thermal degradation,in which the first stage involved the dehydration of MH and decarboxylic reaction of EVA and the second one involved the thermal pyrolysis of polymer main chain and volatilization of residues.%采用两步熔融共混法制备了硅烷接枝交联乙烯-醋酸乙烯酯共聚物(EVA)/聚丙烯(PP)/氢氧化镁(MH)复合材料,研究了乙丙嵌段共聚聚丙烯(PP-B)和等规均聚聚丙烯(PP-H)分别与EVA混合后的硅烷接枝交联的效率,用万能拉力试验机、热延伸试验仪、极限氧指数仪及垂直燃烧仪等研究了EVA/PP/MH复合材料的力学、热延伸和阻燃等性能.结果表明,EVA/PP-B共混物进行硅烷交联的效果优于EVA/PP-H共混物;MH含量≤120份(质量份,下同)时,硅烷交联EVA/PP/MH达到了交联度标准要求;随着MH含量由80份增加到160份,未交联EVA/PP-B/MH的极限氧指数由25.0％增大到32.2％,交联后极限氧指数比交联前提高了0.5 ％～1.5％;当MH含量≥120份时,EVA/PP-B/MH垂直燃烧能达到V-0级;EVA/PP-B/MH的热失重过程分2个阶段,第一个热分解阶段主要为MH失水和EVA的脱羧反应,第二个热分解阶段主要对应于PP-B和EVA主链结构的裂解和残渣的挥发.
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