Poly(3-hydroxybutyrate) Modified with Thermoplastic Polyurethane and Microfibrillated Cellulose: Hydrolytic Degradation and Thermal and Mechanical Properties

Blending poly(3-hydroxybutyrate) (PHB) with other polymers could be a rapid and accessible solution to overcome some of its drawbacks. In this work, PHB was modified with microfibrillated cellulose (MC) and a thermoplastic polyurethane containing biodegradable segments (PU) by two routes, using a masterbatch and by direct mixing. The PU and MC modifiers improved the thermal stability of PHB by up to 13 °C and slightly decreased its melt viscosity and crystallinity, thus improving the melt processability. The addition of PU in PHB composites led to a decrease in the storage modulus, which did not exceed 20% at room temperature. The hydrolytic degradation in an alkaline environment at 50 °C for 28 days decreased the thermal stability of the composites by 58-65 °C, while the lower mass loss and morphological features showed that the PU modifier delayed the degradation of the PHB composites. The improved thermal stability, melt processability, and lower cost, along with higher flexibility and the possibility of controlling the hydrolytic degradation by the PU content, make the PHB/PU/MC composites obtained by the masterbatch method promising materials for medical and engineering applications.