Improvement of flame retarding performance of polyolefin based cable outer sheath

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 is systemically investigated. The mechanical, thermal, flame-retardant, and morphological properties of obtained compounds are 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 which is containing metal hydroxide-based ATH with 60%wt as a flame-retardant additive. Different IFRs ratio from 25 to 60%wt is used in compound receipts. The reduction of IFRs ratio from 40 to 25%wt not only improved tensile strength and elongation at break values but also provided to mandatory flammability requirements of the ST8 type cable standard. The introduction of organomodified SP nanoclay as an anti-dripping agent with 3 and 5%wt into the compounds has been slightly improved the LOI values between 27 and 30%. Thermal properties of compounds in the absence or presence of SP nanoclay are 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 are significantly improved by incorporation of both IFR and SP nanoclay. Furthermore, the addition of SP nanoclay an anti-dripping agent reduces the burning rate, limiting the heat and mass transfer on the surface that proved as a smoother and more compact carbonaceous residue with less cracks and holes on their surface by SEM analysis