The influence of the compatibilizer on the morphology and thermal properties of polypropylene layered double hydroxide composites

Polypropylene (PP)/layered double hydroxide (LDH) composites were prepared via melt-compounding using both a carbonate-LDH and an organo-LDH (dodecyl benzene sulfonate DBS-LDH) in different concentrations. Transmission electron microscopy and X-ray diffraction analysis were used to investigate the morphology. The results showed that only by using DBSLDH the intercalation of polymer chains and a partial delamination were obtained. However, the introduction of maleic anhydride-grafted polypropylene (PP-g-MAH), as coupling agent, favored the aggregation of the particles generating localized domains of aggregates. The thermo-gravimetric analysis showed that PP/DBS-LDH composites have a higher thermal stability than the pure matrix. Differential scanning calorimetry evidenced that both LDH and DBS-LDH particles acted as nucleating agents increasing the crystallization temperature, even if, in the case of LDH the effect was observed only with the addition of the compatibilizer. The results collected by dynamic mechanical thermal analysis, beyond showing a significant increase of the matrix stiffness by incorporation of DBS-LDH, evidenced an increase of the PP glass transition temperature (Tg) indicating a restriction of PP chain segment mobility due to the strong polymer-particle interactions.