Flame retardant, mechanical, and hot air aging properties of ethylene-propylene-diene monomer/ammonium polyphosphate/nano-silic composite rubber

In this work, effect of the ratio of nonhalogenated flame retardants (ammonium polyphosphate [APP] and nano-silica [nano-SiO2]) on the mechanical, thermal, and flame retardant properties of ethylene-propylene-diene monomer (EPDM) composite rubber were investigated. Vulcanization characteristics, high temperature compression permanent deformation, thermal oxygen aging, dynamic thermodynamic analysis, thermal stability, cone calorimetry, limiting oxygen index (LOI), horizontal vertical combustion (UL-94), and scanning electron microscopy were carried out. The experimental results showed that the mechanical properties of the composite rubber decreased with the addition of APP. However, the addition of nano-SiO2 was found to significantly improve the mechanical properties of the composite rubber when it was incorporated. In terms of flame retardant properties of EPDM composite rubber, the combination of APP and nano-SiO2 has a synergistic flame retardant effect in comparison to the use of single APP flame retardant. The heat release rate of EPDM composite rubber decreased by 34%, the total heat release decreased by 19%, the LOI increased by 76%, and the flame retardant grade of EPDM composite rubber reached V-0. The EPDM composite rubber fabricated in the present study showed excellent fire resistance and desirable mechanical properties, which are of practical significance for further expanding the application ranges of EPDM rubbers.