Flame-retardant properties of nanoclay-filled thermoplastic polyurethane/polypropylene nanocomposites

The flame retardancy, mechanical properties of a pure polypropylene (PP)/(thermoplastic polyurethane) (TPU) blend, and PP/TPU blends containing nanoclay as flame retardants, were investigated by the limiting oxygen index (LOI) test, vertical burning test (UL-94), rate of burning test (ASTM D 635), and their effect on relevant mechanical properties. The LOI value of the neat PP/TPU blend was 18% and those of the halogen-based bromine-containing (flame retardant)-based PP/TPU blend and PP/TPU(5% nanoclay-filled)/MA-g-PP (maleic anhydride-grafted-PP) blends were increased by 32% and 28.5% as compared with that of the pure PP/TPU blend, which showed that the above flame retardants and nanoclay could greatly increase the LOI value of the system. However, deterioration of mechanical properties is observed for bromine-containing (flame retardant)-based compositions. The introduction of the nanoclay as the flame retardant to the TPU/PP blend system increased the mechanical properties along with flame-retardant properties. The tensile stress required to make 200% strain in 5% nanoclay added TPU/PP/MA-g-PP nanocomposite increased by 120%, and the flexural modulus increased by 80%–90%. J. VINYL ADDIT. TECHNOL., 23:E72–E80, 2017.