Preparation and structural study of polypropylene–talc gradient materials

Polypropylene (PP)–talc composites with proper spatial gradients were prepared by gradually varying the component ratio of PP and talcum powder during the extrudion process. The gradient variations of composition, structural and physical properties along the radius direction of a cylindrical sample were studied by wide angle x‐ray diffraction (WAXD), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and tensile testing. The WAXD and TG results indicate that the content of either component shows a monotonic change along the radius direction. With increasing radius, a gradually decreased percentage of PP was observed, while that of the talc filler gradually increased. A gradually varying stacking density of the talcum powder in the PP matrix was also observed by the SEM images for the sliced specimens sampled at different positions. As a result of such variations in both component and structure, the physical properties, including the mechanical performance and thermal behaviour of the PP–talc composites, gradually varied along the radius direction. The experimental data show that a polymeric gradient material (PGM), with significantly different structures and properties existing on both sides, can be prepared by using this unique process.