Novel poly(3-hydroxybutyrate) nanocomposites containing WS₂ inorganic nanotubes with improved thermal, mechanical and tribological properties

Poly(3-hydroxybutyrate) (PHB) nanocomposites containing environmentally-friendly tungsten disulphide inorganic nanotubes (INT–WS₂) have been successfully prepared by a simple solution blending method. The dynamic and isothermal crystallization studies by differential scanning calorimetry (DSC) demonstrated that the INT–WS₂ exhibits much more prominent nucleation activity on the crystallization of PHB than specific nucleating agents or other nanoscale fillers. Both crystallization rate and crystallinity significantly increase in the nanocomposites compared to neat PHB. These changes occur without modifying the crystalline structure of PHB in the nanocomposites, as shown by wide-angle X-ray diffraction (WAXS) and infrared/Raman spectroscopy. Other parameters such as the Avrami exponent, the equilibrium melting temperature, global rate constant and the fold surface free energy of PHB chains in the nanocomposites were obtained from the calorimetric data in order to determine the influence of the INT–WS₂ filler. The addition of INT–WS₂ remarkably influences the energetics and kinetics of nucleation and growth of PHB, reducing the fold surface free energy by up to 20%. Furthermore, these nanocomposites also show an improvement in both tribological and mechanical (hardness and modulus) properties with respect to pure PHB evidenced by friction and nanoindentation tests, which is of important potential interest for industrial and medical applications. - Highlights: • Environmentally-friendly INT–WS₂ is used to produce advanced PHB NCPs. • Novel PHB NCPs are obtained without using modifiers or surfactants. • Novel INT–WS₂ improve the thermal and mechanical properties of PHB. • INT–WS₂ is effective in reducing the friction coefficient of PHB. • The benefits of using INTs compared to other nanoscale fillers are highlighted