PP and PBT composites filled with sepiolite: Morphology and thermal behaviour

In this paper, we present the first attempt to correlate structure and thermal properties of sepiolite based composites. Composites were prepared in a Brabender internal mixer with 3 wt.% of pristine or organically modified sepiolites in two different polymer matrices, polypropylene (PP) and poly (butylene terephthalate) (PBT). Characterization of the materials was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A nucleating action was found in both polymeric matrices. Furthermore, PP-composites showed interesting features in the polymer crystalline structure. A linear correlation between TONSET and the intensity ratio of PP-composites diffraction peaks (I/II) could be observed. Despite a catalytic effect induced by pristine sepiolite on PP thermal degradation, this drawback could be reduced by sepiolite surface modification. Moreover, higher stability towards thermoxidation was achieved. On the other end, the thermal behaviour of PBT was not affected by the presence of sepiolite.