A polyester-type polyurethane (PU) was prepared using hydroxyl-terminated natural rubber (HTNR) as the soft polymer segments, 4,4-methylene dicyclohexyl diisocyanate (H12MDI) as the hard segments and 1,4-butane diol (BDO) as a chain extender. A simple one-shot bulk polymerization method using tetrahydrofuran (THF) as the solvent was chosen. The molar ratio of (H12MDI:HTNR:BDO) was fixed at 1.05:0.5:0.5. The pristine PU and its composite films with titanium nanoparticles (TiO2), silver nanoparticles (AgNPs) and benzoic acid (BA) were prepared with a constant 0.5 wt% loading of the antimicrobial fillers. The pristine PU and PU composite films were obtained by solution casting and drying at 60 degrees C in a vacuum oven. The effects of the antimicrobial fillers on the physical structure, mechanical properties, thermal properties, and antimicrobial activities were investigated. The SEM images showed that TiO2 and AgNPs aggregated. The aggregates reduced the films' tensile strength as they obstructed the transfer of mechanical loads from PU matrix to the dispersed fillers. In contrast, BA was clearly well dispersed in the matrix giving much better mechanical properties (12 MPa tensile strength and 278% strain at break) and the PU-BA films were transparent. The PU-BA composites appear promising for biomedical applications. Graphic abstract