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. © 2015 Society of Plastics Engineers