Investigation of the properties of polystyrene-based wood plastic composites: effects of the flame retardant loading and magnetic fields

Polystyrene-based wood plastic composites (WPCs) containing ammonium polyphosphate (APP) and iron (Fe) powder were prepared in this work by solution blending with the aid of an alternating magnetic field. The mechanical, electrical, thermal and fire performances of the WPCs were analyzed through mechanical testing, thermogravimetry and CONE calorimeter. The addition of Fe powder decreased the tensile strength and increased the impact strength. The APP promoted the formation of sufficient char on the material's surface and enhanced the flame retardant properties. Furthermore, an alternating magnetic field was used to align the Fe powders. After the magnetic treatment, the electrical conductivity and thermal properties were found to increase considerably compared with those without treatment. The Agari model presented the most reasonable prediction of thermal conductivity as a function of Fe content among three classical thermal conduction models. According to the morphological observations, the iron particles in the composites tended to rearrange along the direction of the magnetic field after treatment, resulting in the enhancement of both thermal and electrical conductivities. The prepared WPCs in this study exhibited good flame retardant properties together with the acceptable mechanical properties of the composites.