Influence of surface flame-retardant layer containing ammonium polyphosphate and expandable graphite on the performance of jute/polypropylene composites

Surface flame-retardant layer containing ammonium polyphosphate (APP) and expandable graphite (EG) combined with polypropylene (PP) was used to improve the flame retardancy and mechanical properties of jute/PP nonwoven felts composites. The flame retardancy of jute/PP composites had been investigated by limit oxygen index (LOI), horizontal burning rate (HBR) and cone calorimeter. The results showed that the jute/PP composites with APP/EG-retardant layer were less flammable with higher LOI value, longer time to ignition, lower value of the peak heat release rate, total heat release, effective heat combustion, total smoke production, and became self-extinguished in HBR test. The thermal degradation and residual structure of jute/PP composites were monitored by thermogravimetric analyses, Fourier transform infrared, X-ray photoelectron spectroscopy and scanning electron microscope. These results revealed that the char residual amount and the element of carbon in the residual char resulted by APP/EG were much higher than the values by APP and EG individually. The flame-retardant properties of J/P composites were enhanced greatly by the combination of APP and EG even the amount of flame retardant is only 5%. Furthermore, the mechanical properties of jute/PP composites were also enhanced by the surface flame-retardant layer.