Abstract Although widely used in industrial applications, epoxy resins generally display low toughness and high flammability. The use of phosphorus compounds can improve flame-retardant capabilities along with reducing mechanical properties. Herein, the novel flame-retardant additive of phosphorous-linked epoxidized vegetable oil (P-L-EVO) was fabricated from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and epoxidized vegetable oil through a ring opening reaction before applying it as additive for an epoxy/silica system. The silica was extracted from a rice husk using a combined approach of acid treatment and thermal treatment. Successful grafting and extraction reactions were confirmed using Fourier transform infrared analysis (FTIR) and nuclear magnetic resonace (NMR). The epoxy resin-based samples were cured with diethylenetriamine (DETA) hardener at ambient conditions. The influences of additives on the mechanical properties and flame-retardant capabilities were examined via tensile strength, impact strength, critical stress intensity (KIC), a cone calorimeter, the limited oxygen index (LOI), and the UL 94 vertical test. The epoxy sample with 20 wt.% silica and 10 wt.% of P-L-EVO (S20.10) reached the LOI value of 35.89 % and a V0 rating of UL94. Moreover, this combination improved the impact strength, tensile strength, and KIC by up to 90.16 %, 20.28 %, and 73.84 %, respectively in comparison with pristine epoxy sample (S00.00). The formation of a non-thermal decomposition char layer along with a release of flame-retardant radicals was considered the novel flame-retardant mechanism.

中文翻译：

---

磷连接环氧化植物油对二氧化硅增强环氧复合材料力学行为和可燃性的影响

摘要 环氧树脂虽然在工业应用中得到广泛应用，但普遍表现出低韧性和高可燃性。使用磷化合物可以提高阻燃能力，同时降低机械性能。在此，由 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) 和环氧化植物油通过环合成磷连接环氧化植物油 (PL-EVO) 的新型阻燃添加剂。在将其用作环氧树脂/二氧化硅系统的添加剂之前进行开孔反应。使用酸处理和热处理相结合的方法从稻壳中提取二氧化硅。使用傅里叶变换红外分析 (FTIR) 和核磁共振 (NMR) 证实了成功的接枝和提取反应。基于环氧树脂的样品在环境条件下用二亚乙基三胺 (DETA) 硬化剂固化。通过拉伸强度、冲击强度、临界应力强度 (KIC)、锥形量热仪、极限氧指数 (LOI) 和 UL 94 垂直测试来检查添加剂对机械性能和阻燃能力的影响。含有 20 wt.% 二氧化硅和 10 wt.% PL-EVO (S20.10) 的环氧树脂样品达到 35.89% 的 LOI 值和 UL94 的 V0 等级。此外，与原始环氧树脂样品 (S00.00) 相比，这种组合将冲击强度、拉伸强度和 KIC 分别提高了 90.16%、20.28% 和 73.84%。非热分解炭层的形成以及阻燃自由基的释放被认为是新的阻燃机制。