Study on the flame retardancy of thermoplastic elastomers composites applied for cable sheath

The halogen-free flame retardant (HFFR) thermoplastic elastomers (TPEs) composites filled with aluminum diethylphosphinate (ADP) had been prepared using the melting compounding method by a twin-screw extruder. The flame retardancy, smoke release performance, thermal stability, mechanical properties and microscopic morphology of carbonaceous char of TPE/ADP composites had been investigated by cone calorimeter, NBS smoke density chamber, limiting oxygen index (LOI), UL-94 (vertical flame) test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and ultimate tensile. The study results indicated that the flame retardancy and char forming characteristics of TPE/ADP composites had been dramatically improved. The more significant expansion of flame retardant TPE/ADP composites during combustion was found with the addition of synergistic flame retardants Zinc Borate (ZB) or melamine cyanurate (MCA). Among the synergistic agents of organic montmorillonite (OMMT), ZB, and MCA, ZB exhibited the best assisted carbonization performance regardless of high or low heat flux, and formed a multi-level twisted carbonaceous char structure. Meanwhile, due to the addition of synergistic flame retardant ZB, not only the flame retardancy was improved, but also the smoke release was significantly inhibited. The tensile performance test showed the ultimate tensile strength and elongation at break of TPE composites maintained a relatively high level, and which can meet the application requirements of cable sheath materials.