Flame Retardancy of Thermoplastic Polyurethane Using Phosphorus-containing Flame Retardants

Abstract

A new phosphorus-containing polymer was synthesized and applied as a flame retardant in the polyether thermoplastic polyurethane (TPU). This flame retardant combined with two commercial flame retardants of melamine pyrophosphate (MPP) and melamine cyanurate (MCA) were also used in TPU. Their flame retardancy, thermal degradation and structural feature were investigated by limiting oxygen index (LOI), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The experimental data showed that the presence of phosphorus-containing flame retardant improve the limiting oxygen index, thermal stability and fire behavior. The LOI value of TPU including 20 wt% synthesized phosphorus-containing flame retardant and 20 wt% MCA was increased to 25.8. The thermal stability of TPU was also excellently improved comparing with the neat TPU. A maximum char residue was obtained when 20 wt% synthetic flame retardant and 20 wt% MPP were added into the TPU which the char yields were 18.7%. The combustion heat results showed that the value of neat TPU is highest than other TPUs by adding the different flame retardants. The SEM results showed that a dense char layer was obtained by adding the synthetic phosphorus-containing flame retardant and MCA with 20 wt % respectively into the TPU system.