Mechanical properties and morphology of intumescent flame retardant filled polypropylene composites

The intumescent flame retardant (IFR) filled polypropylene (PP) composites were prepared using a twin‐screw extruder. The tensile and impact fracture behavior of the composites were measured at room temperature. It was found that the Young's modulus increased roughly, while the tensile strength decreased slightly with increasing the IFR weight fraction; the toughening effect of the filler on the PP resin was significant. Both the V‐notched Izod impact strength and the V‐notched Charpy impact strength of the PP/IFR composites showed a nonlinear increase with increasing the filler weight fraction ( φ f ) as φ f was less than 20%, then it decreased. The limited oxygen index of the composites increases nonlinearly with increasing φ f . The relationship between them obeyed a quadratic equation. The impact fracture surface was observed by means of a scanning electronic microscope to understand the toughening mechanisms for the composite systems.