In-situ functional modification of the inner and outer surfaces of mesoporous silica SBA-15 towards improving fire safety and thermal stability of epoxy resins

The inflammability of epoxy resins (EPs) severely limits their safe and reliable application. The design and application of flame retardants has enormous potential for increasing the fire safety of EP composites. In the present study, a novel organic-inorganic nanohybrid material (VDSZ), consisting of mesoporous silica (SBA-15), P/N/Si-containing compound and the transition metal (Zn), was constructed by in-situ functional modification of the inner and outer surfaces of SBA-15. That is, Zn was in-situ modified on the inner pore surface of SBA-15, and phosphorus-containing compound was in-situ grafting onto outer surface of SBA-15 by Schiff base reaction. The results showed that EP/VDSZ-3 composite had a significant improvement in flame-retardant properties. The limiting oxygen index (LOI) for EP/VDSZ-3 increased from 24.5 % (EP) to 30.8 %, resulting in a UL-94 V-0 rating. Furthermore, the findings of the cone calorimeter test (CCT) demonstrated that, in comparison with pure EP, the peak heat release rate, total smoke generation and smoke production release of EP/VDSZ-3 decreased by 29.16 %, 25.95 %, and 30.90 % respectively. Moreover, the impact strength of EP/VDSZ-1 was 40 % higher than that of pure EP. Meanwhile, the thermal stability of EP composites improved dramatically as the VDSZ increased. This study found that creating a multi-level structure provided a fresh idea for simultaneously boosting polymer flame retardancy, smoke suppression and thermal stability, which will be applied to building materials with flame retardant requirements.