Utilization of waste shellac resin to synthesize thermally stable crosslinked shellac nanoparticles via wet grinding technique for high-barrier packaging

In this study, shellac waste has been used to produce crosslinked shellac nanoparticles via dry grinding and wet grinding in a ball mill. The developed shellac waste nanoparticles’ size was 113.15 nm with a zeta potential of − 25.69 ± 3.59 eV. Field emission scanning electron microscopy confirmed that the size of the crosslinked shellac nanoparticles was in the range of 35–180 nm, possessing a spherical shape. Fourier transform infrared spectroscopy confirmed the formation of complex crosslinked esters of shellac after curing, and differential scanning calorimetry was performed to determine the formation of thermoset material. The developed shellac nanoparticle waste was also used for coating of paper with PLA, resulting in a maximum contact angle of 132.81°, suggesting its hydrophobic behavior. Furthermore, WVTR was reduced to 58.25 g/m2-day from 97.04 g/m2-day when 1% nano-crosslinked shellac was used. The incorporation of crosslinked shellac nanoparticles in PLA and coating on the paper increased the water barrier by 43%. These results suggest that the crosslinked shellac nanoparticles from waste shellac can be utilized for barrier coating in paper and tertiary packaging and can serve as an alternative to the petroleum-based coating material.