Glass fibers (GFs) reinforced polymer composites display high mechanical performance but deteriorated flame retardancy due to the “candlewick effect” caused by fibers. To solve this problem, novel hierarchal hybrid glass fibers (GF@HBPPA@GO) were prepared by multistep coating of 3-aminopropyltriethoxysilane (APTES), hyperbranched polyphosphoramide (HBPPA) and graphene oxide (GO) in sequence. Several GFs reinforced poly(lactic acid) (PLA) composites were fabricated with the same GFs loading. PLA/GF@HBPPA@GO composite showed the highest limited oxygen index (LOI) value of 25.2% and much decreased peak heat release rate, total heat release and mass loss rate, corresponding to a drop of 23.2%, 16.6%, and 53.8% respectively compared with PLA/GF-APTES composite. Meanwhile, it maintained similar tensile and impact strength values. The improved flame retardancy was mainly attributed to the good synergistic effect of HBPPA and GO on generating high-yield char residues encapsulating GFs perfectly in the condensed phase, which effectively reduced the interface energy and increased the surface roughness of GFs to suppress the wetting and spreading of PLA melt toward the flame zone, and consequently weakened the candlewick effect of GFs and achieved better flame retardancy. This provides new ideas for preparing fiber reinforced polymer composites with encouraging mechanical properties and outstanding fire safety simultaneously.

中文翻译：

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超支化聚磷酰胺和氧化石墨烯片改性的多级杂化玻璃纤维提高阻燃性和抑制聚（乳酸）/玻璃纤维复合材料的烛芯效应

玻璃纤维 (GF) 增强聚合物复合材料显示出高机械性能，但由于纤维引起的“烛芯效应”，阻燃性变差。为了解决这个问题，通过依次多步涂覆 3-氨基丙基三乙氧基硅烷 (APTES)、超支化聚磷酰胺 (HBPPA) 和氧化石墨烯 (GO)，制备了新型多级混合玻璃纤维 (GF@HBPPA@GO)。使用相同的 GF 负载量制造了几种 GF 增强聚乳酸 (PLA) 复合材料。PLA/GF@HBPPA@GO 复合材料的极限氧指数 (LOI) 最高，为 25.2%，峰值放热率、总放热率和质量损失率大幅下降，分别下降 23.2%、16.6% 和 53.8% % 分别与 PLA/GF-APTES 复合材料相比。同时，它保持了相似的拉伸强度和冲击强度值。阻燃性的提高主要归因于 HBPPA 和 GO 良好的协同作用，产生高产率的焦炭残留物，将 GFs 完美地包裹在凝聚相中，有效降低界面能，增加 GFs 的表面粗糙度，从而抑制润湿和铺展PLA 向火焰区熔化，从而削弱了 GF 的烛芯效应，实现了更好的阻燃性。这为制备同时具有令人鼓舞的机械性能和出色的防火安全性的纤维增强聚合物复合材料提供了新思路。有效降低了GFs的界面能，增加了GFs的表面粗糙度，抑制了PLA熔体向火焰区的润湿扩散，从而削弱了GFs的烛芯效应，获得了更好的阻燃性能。这为制备同时具有令人鼓舞的机械性能和出色的防火安全性的纤维增强聚合物复合材料提供了新思路。有效降低了GFs的界面能，增加了GFs的表面粗糙度，抑制了PLA熔体向火焰区的润湿扩散，从而削弱了GFs的烛芯效应，获得了更好的阻燃性能。这为制备同时具有令人鼓舞的机械性能和出色的防火安全性的纤维增强聚合物复合材料提供了新思路。