Thermal degradation mechanism and flame retardancy of MQ silicone/ epoxy resin composites

A series of flame-retarded epoxy resins (EP) loaded with methyl MQ silicone resin and a novel hyperbranched polysiloxane (HPSi) acting as compatibilizer have been prepared. Compatibility of these EP composites was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that HPSi significantly improved the compatibility of EP/MQ. The flame retardancy and thermal degradation behavior of these EP composites were investigated by limiting oxygen index (LOI), UL-94 vertical burning, themogravimetric analysis test (TG), FTIR and SEM. The results showed that the incorporation of MQ into EP can improve the thermal stability dramatically. It is observed that the LOI values of epoxy resins increased obviously (from 21% to 31%) with the MQ loading, which passed V-0 rating of UL-94. Specifically, its combustion residue at 700 °C was 14.5% weight, which exceed the value of neat EP resin (5.08% weight). Moreover, structural analysis of the remaining after vertical burning by FTIR spectra verified the formation of polyaromatic carbons. Additionally, morphology of the residue char showed the compact, smooth, and tight structure of EP composites systems. These outstanding integrated properties would make EP composites attractive for practical applications.