This paper presents an attempt to improve the properties of poly(3-hydroxybutyrate) (P3HB) using linear aliphatic polyurethane (PU400) and organomodified montmorillonite (MMT)-(Cloisite®30B). The nanostructure of hybrid nanobiocomposites produced by extrusion was analyzed by X-ray diffraction and transmission electron microscopy, and the morphology was analyzed by scanning electron microscopy. In addition, selected mechanical properties and thermal properties were studied by thermogravimetric analysis, TGA, and differential scanning calorimetry, DSC. The interactions of the composite ingredients were indicated by FT IR spectroscopy. The effect of the amount of nanofiller on the properties of prepared hybrid nanobiocomposites was noted. Moreover, the non-equilibrium and equilibrium thermal parameters of nanobiocomposites were established based on their thermal history. Based on equilibrium parameters (i.e., the heat of fusion for the fully crystalline materials and the change in the heat capacity at the glass transition temperature for the fully amorphous nanobiocomposites), the degree of crystallinity and the mobile and rigid amorphous fractions were estimated. The addition of Cloisite®30B and aliphatic polyurethane to the P3HB matrix caused a decrease in the degree of crystallinity in reference to the unfilled P3HB. Simultaneously, an increase in the amorphous phase contents was noted. A rigid amorphous fraction was also denoted. Thermogravimetric analysis of the nanocomposites was also carried out and showed that the thermal stability of all nanocomposites was higher than that of the unfilled P3HB. An additional 1% mass of nanofiller increased the degradation temperature of the nanocomposites by about 30 °C in reference to the unfilled P3HB. Moreover, it was found that obtained hybrid nanobiocomposites containing 10 wt.% of aliphatic polyurethane (PU400) and the smallest amount of nanofiller (1 wt.% of Cloisite®30B) showed the best mechanical properties. We observed a desirable decrease in hardness of 15%, an increase in the relative strain at break of 60% and in the impact strength of 15% of the newly prepared nanobiocomposites with respect to the unfiled P3HB. The produced hybrid nanobiocomposites combined the best features induced by the plasticizing effect of polyurethane and the formation of P3HB-montmorillonite-polyurethane (P3HB-PU-MMT) adducts, which resulted in the improvement of the thermal and mechanical properties.
Keywords: aliphatic polyurethane; modified montmorillonite; nanobiocomposites; nanoclay; polyalcanoates; properties modification.