Effects of nanoclay and phenolic resin in combination with DOPO derivative on flame retardancy, thermal and thermomechanical properties of epoxy resin

Various flame-retardant epoxy (EP) composites were prepared in combination with phenolic resin (PF), DOPO derivative (DD) and nanoclay (NC). The flame-retardancy of epoxy composites was studied by LOI, UL-94 and cone calorimeter analyses. The EP‒DD _2.0 (2.0% phosphorus) and EP‒DD _2.0 ‒NC _2.0 (2.0% phosphorus and 2.0% NC) composites gave best V-0 rating without dripping and LOI values of 29.0–29.2%. In cone calorimeter analysis, the peak heat release rate and total heat release were decreased by 63.6 and 59.1% for EP‒DD _2.0 ‒NC _2.0 nanocomposite. The epoxy composites on heating exhibited higher char yield at the cost of volatile products as noted in thermogravimetric and cone calorimetry analyses. The DSC and DMA were carried to measure the glass transition temperature ( T _g ). The results indicated a significant drop in T _g from 213°C of EP to 146°C of EP-DD _2.0 -NC _2.0 , while an improvement in storage modulus was observed of the sample by decreasing the cross-link density as a result of plasticization effect of flame-retardant.