Bifunctional epoxy coatings containing new nano-hybrid based on lignin for decoration and gamma radiation shielding

Recently, researchers focused on utilizing agricultural waste, such as rice straw, to prepare eco-friendly green compounds that have industrial applications, rather than burning it, which leads to environmental problems. In this study, a new Mn (lignin/silica/fatty acid) nano-hybrid Mn(LSF) was deposited from the black liquor of rice straw and then mixed with epoxy to prepare bifunctional epoxy coatings for decoration and gamma radiation shielding. The chemical structure and morphology of the Mn(LSF) nano-hybrid were confirmed by FTIR, XRF SEM, EDX, mapping, and TEM. After the synthesis, Mn(LSF) nano-hybrid was integrated into epoxy resin with three proportions (e.g., 2%, 4%, and 8%), and then each coating was painted on plastic substrates with three thicknesses (e.g., 100 μm, 150 μm, and 200 μm) to investigate the effect of the concentration and thickness on the degree of color and gamma radiation shielding. The results revealed that the evaluated Mn(LSF) nano-hybrid is synthesized in nanoscale and its main elements, such as manganese, silica, and carbon, are distributed homogenously in the lignin base. Moreover, the color measurements elucidated that the lightness decreases with increasing the concentration and the thickness; therefore, the darkness increases. Furthermore, the γ-ray shielding ability of the prepared coatings containing Mn(LSF) nano-hybrid throughout an energy range of 0.662, 1.173, and 1.332 MeV emitted by the radioactive sources Cs-137 and Co-60 was measured using the narrow beam transmission method and a NaI (Tl) scintillation detector. The measurements depict an enhancement in the linear attenuation coefficient with increasing the Mn(LSF) nano-hybrid substitution in the coatings. The linear attenuation coefficient increased by 17.83%, 18.30%, and 18.14% at 0.662 MeV, 1.173 MeV, and 1.332 MeV, respectively, as Mn(LSF) nano-hybrid rise across the concentration of 2% to 8%.