Dynamic mechanical analysis (DMA) is used to study the dynamic mechanical properties of injection-moulded discs of polypropylene, talc-filled polypropylene composites and silane-treated talc-filled polypropylene composites. Silane addition in a very low proportion improves the adhesion between the filler and the polymer and enables composites to be used where otherwise they could not. Therefore, on the one hand, the composites have different properties due to the filler and the coupling agent, and on the other hand the injection processing induces a structure, resulting in inhomogeneity and anisotropy for the moulded discs. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) techniques are used to help state the microscopic structure and justify the macroscopic properties measured with DMA.