Influence of chain length, particle size, and thermal treatment of dicarboxylic acid-functionalized titanium dioxide filler in polypropylene

The influence of size and thermal treatment of titanium dioxide (TiO2) functionalized with dicarboxylic acids of different length chains on the crystallization of isotactic polypropylene (iPP) has been investigated. The functionalization and crystallization were analyzed by FTIR, DSC, XRD, and mechanical tests. The chain length is crucial, while glutaric acid favored α-nucleation, pimelic and azelaic promoted β-crystals. Pimelic acid was the best by increasing β-crystals up to 54.1% compared with pure iPP (4.7%). Regarding particle size, the smallest dimension increased β-nucleation by ~ 32%. While thermal treatment was applied, β-crystal content increased by ~ 22.7%. Regarding mechanical properties, the fillers presence decreased tensile stress and stiffness since the high content of β-crystals decrease elastic modulus. These results offer evidence that it is possible to prepare fillers able of selecting the type of crystallization since functionalized-TiO2 can promote α- or β-crystals by varying particle size, functionalization agent, and applying a thermal treatment. However, more detailed studies are needed to confirm these observations.