Influence of organically modified clays on the properties and disintegrability in compost of solution cast poly(3-hydroxybutyrate)

Polymer nanocomposites, based on a bacterial biodegradable thermoplastic polyester, poly(hydroxybutyrate) (PHB), and unmodified montmorillonite Cloisite Na+ (CNa) and chemically modified Cloisite 15A and 93A (C15A and C93A), were prepared through a solution route. The nanostructure has been established through X-ray diffraction (XRD), while the nanocomposites were characterized by differential scanning calorimetry (DSC), contact angle measurements, and thermogravimetric (TGA) analysis. Disintegrability in composting conditions has been tested at certain times (0, 7, 14, 21, 28 and 35 days at 58 °C) and the effect of different nanoclays on the properties of biodegraded films was deeply investigated. XRD results suggest a better dispersion for C15A and C93A based nanocomposites that present also a more surface hydrophobic nature respect to PHB matrix and PHB nanocomposite loaded with unmodified Cloisite. This result is in accord with disintegrability behavior of PHB nanocomposites. Visual observation, chemical, thermal and morphological investigations proved that the disintegration in composting conditions was faster for PHB_4CNa respect to the systems loaded with modified clays suggesting the possibility to modulate the disintegrability capacity of PHB selecting a specific filler.