Green Synthesis of Alkyd Resins from Rubber Seed Oil Functionalized with Metal Oxide Nanoparticles and Garlic Extract: Characterization and Enhanced Antibacterial Activity

Abstract

This study presents the synthesis, characterization, and antibacterial evaluation of bio-based 
alkyd resins derived from rubber seed oil. The fatty acid composition was analyzed using 
Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography–Mass 
Spectrometry (GC-MS), while physicochemical properties were determined following 
Association of Official Analytical Chemists (AOAC) standard methods. Refined rubber seed 
oil (RRO) showed enhanced qualities over crude oil, with iodine value (96 g I₂/100 g), acid 
value (0.9 mg KOH/g), saponification value (195.74 mg KOH/g), refractive index (1.48), 
viscosity (100), and density (0.91). Alkyd resins were synthesized via alcoholysis and 
polyesterification and classified into short, medium, and long oil types. Acid values decreased 
during polymerization, with the long oil resin having the lowest (7.60 ± 0.40 mg KOH/g), the 
medium oil resin achieved the highest degree of polymerization (Dp = 4.15) and functional 
group conversion (76%). Nanoparticles (CuO, ZnO, TiO₂) at 2% and 4% (wt/wt) were 
incorporated and further functionalized with garlic extract to improve antimicrobial 
performance. Long oil alkyd resins with hybrid nanoparticles and garlic showed the strongest 
antibacterial activity, with inhibition zones reaching 40.5 mm against Staphylococcus aureus. 
These results support the development of green, multifunctional coatings for applications in 
biomedical, packaging, and environmental sectors.