Novel Research on Selected Mechanical and Environmental Properties of the Polyurethane-Based P3HB Nanobiocomposites

This study focused on hybrid nanobiocomposite polymers produced with the use of poly(3-hydroxybutyrate), P3HB and aliphatic polyurethane (PU) as a matrix, including variable quantities of organomodified montmorillonite (Cloisite^®30B). Mechanical, thermal, and biodegradability tests were conducted to evaluate their properties. The nanobiocomposites were tested using monotonic tensile tests, which revealed that the addition of PU and organomodified montmorillonite reduced the stiffness and strain at break compared to native P3HB. The material's yield strength was higher for P3HB, while the PU-modified composites exhibited lower stiffness and increased ductility, especially with lower amounts of clay. Scanning electron microscopy (SEM) images showed that cracks in the samples propagated more rapidly as the clay content increased. The bending test showed that the P3HB-PU composites and the nanobiocomposites exhibited lower bending strength and elongation at break compared to pure polyester. However, the composites with lower clay content showed better performance, suggesting that clay promotes ductility to some extent. The Charpy impact tests indicated an increase in impact strength for the composites with the addition of PU and montmorillonite, especially for the samples with 1 wt.% clay. Biodegradability testing showed that P3HB has a biodegradability of 63.21%. However, the addition of clay reduced biodegradability, with a notable decrease as the clay content increased. The biodegradation of composites with 1 and 2% by mass clay was higher than that of P3HB. Thermal analysis indicates an improvement in the thermal stability of the nanomaterials, with the 1% by mass clay sample showing the highest decomposition onset temperature (263 °C). Overall, the study demonstrated that the presence of PU and montmorillonite moderated the mechanical and thermal properties and biodegradation of P3HB, with the optimal performance observed in the composites with 1% by mass clay.