SYNERGISTIC EFFECTS OF MIXED TANNIN EXTRACTS ON THE PHYSICOMECHANICAL PROPERTIES OF TANNED LEATHER

Abstract

This study evaluates the synergistic effects of mixed tannin extracts from Bagaruwa (Mimosa), Parkia biglobosa, Divi-divi, and their combinations on the physicomechanical properties of tanned leather. Mechanical testing revealed that samples treated with mixed tannins exhibited enhanced tensile strength, elongation, and force resistance compared to single-tannin treatments. Notably, the Bagaruwa-Mimosa combination (Sample BI) achieved the highest force resistance (39.15 kg) and tensile strength (15.07 MPa), whereas Parkia biglobosa only treatments showed lower strength and flexibility. Addition of metabisulphite to Parkia tannin improved mechanical performance, confirming additive synergy. Thermal stability measured by shrinkage temperature varied significantly across samples, with highest values reaching 85.0°C (Sample III), indicating superior hydrothermal resilience in mixed tannin treatments. Water vapor permeability and water absorption tests demonstrated that tannin composition influences leather breathability and moisture retention, essential for application-specific requirements. Indentation indices highlighted the trade-off between softness and durability, with mixed tannin-treated samples achieving balanced profiles suitable for flexible and load bearing uses. Apparent density measurements reflected structural integrity differences correlating with mechanical and absorption properties. These findings confirm that tailored combinations of indigenous tannins can optimize leather quality by enhancing mechanical strength, thermal stability, and moisture management. This work provides a scientific basis for developing advanced tanning formulations targeting improved sustainability and functional performance.