Solvent selection governs the performance of low-quality cat’s eye damar resin as a bio-based coating for biomass composite roof tiles

Abstract

The growing demand for sustainable construction materials has increased interest in bio-based coatings from renewable resources. This study investigated the effect of solvent type on the performance of Cat’s Eye damar resin as a protective coating for sorghum bagasse composite roof tiles. Five solvents with distinct physicochemical characteristics (toluene, butyl acetate, propanol, ethyl acetate, and butanol) were used at a nominal resin-to-solvent ratio of 30:70 (w/w) and applied at a target rate of 110 g/m2. The coated composites were evaluated for physical, mechanical, surface, and wettability properties, while Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to characterized the resin coating. Solvent type significantly affected density, water absorption, thickness swelling, modulus of elasticity, modulus of rupture, surface roughness, equilibrium contact angle, and apparent contact-angle, but did not significantly affect solid content or moisture content. Among the formulations, propanol provided the most balanced performance, producing the highest density (0.83 g/cm3), lowest water absorption (33.04%), low thickness swelling (8.82%), and highest modulus of elasticity (3768 MPa) and modulus of rupture (10.55 MPa). FTIR showed that the principal chemical functionalities of the damar resin were retained after formulation, while XRD patterns remained predominantly amorphous despite differences in relative crystallinity. These findings demonstrate that solvent selection is an important formulation parameter for tailoring the physical, mechanical, surface, and wettability performance of damar-resin coatings on lignocellulosic composites.