Synergistic effect of organically modified sepiolite clay in intumescent flame retardant polyolefin elastomer-based cable outer sheath compounds

The synergistic effect of organically modified sepiolite nanoclay (SP) in conjunction with aluminum polyphosphate/pentaerythritol as an intumescent flame retardant (IFR) additive on the polyolefin elastomer/linear low-density polyethylene compound has been systemically investigated. The mechanical, thermal, flame-retardant, and morphological properties of the obtained compounds were analyzed by tensile test, thermogravimetric analysis, fire testing technology limiting oxygen index analyzer, cone calorimeter, and scanning electron microscopy and compared with the reference compound containing 60% (by wt) of aluminum trihydroxide (ATH) as a flame-retardant additive. The reduction of IFR content from 40 to 25% not only improved the tensile strength and elongation-at-break values it furthermore provided the mandatory flammability requirements of the ST8 type cable standard. The addition of 3 and 5% (by wt) of organomodified SP nanoclay as an anti-dripping agent into the compounds slightly improved the LOI values between 27 and 30%. Thermal properties of the compounds in the absence/presence of SP nanoclay were slightly improved by increasing IFR concentration. According to cone calorimeter results, the flammability parameters of the compounds such as heat release rate and total heat release values were significantly improved by incorporation of both IFR and SP nanoclay. Also, the addition of SP nanoclay as an anti-dripping agent reduced the burning rate and limited the heat and mass transfer on the surfaces. It was confirmed by SEM analysis that these surfaces were smoother and more compact carbonaceous residue with fewer cracks and holes. [GRAPHICS] .

Automated summary

The synergistic effect of organically modified sepiolite nanoclay (SP) in conjunction with aluminum polyphosphate/pentaerythritol as an intumescent flame retardant (IFR) additive on the polyolefin elastomer/linear low-density polyethylene compound has been studied. The addition of SP nanoclay slightly improved the LOI values and thermal properties of the compounds, while reducing the burning rate and improving the flammability parameters.