Eco-friendly coating materials for paper packaging

Recently, a hydrophobic, moisture resistant and biorenewable paper coating derived from castor oil based epoxy methyl ricinoleate with repulpable potential has been presented.

A paper bag with rice.
Test results highlight the great potential of tung oil photopolymerisable coating formulations as a simple and promising alternative for the fabrication of more sustainable and functional paper packaging materials.  Image source: congerdesign - Pixabay (symbol image).

After ban on single-use plastics, completely bio-based coating on paper is in great demand to replace the plastics liner and other organic-inorganic hybrid coating. To resolve the issues like moisture, hydrophilicty and repulpability after use, a green, sustainable and hydrophobic bio-coating material for paper substrate has been developed. Silanised castor oil (SCO) and silanised methyl ricinoleate (SMR) bio-resins have been synthesised by structural modifications of epoxidised castor oil through transesterification and silanisation process. Subsequently, the silylated bio-resins have been hydrolysed and subjected to crosslinking with cellulosic paper substrate through condensation process.

High hydrophobicity

The coated papers showed hydrophobicity with a water contact angle (WCA) up to 97° and strongly moisture resistance (moisture content of 2–3%). Aditionally, the papers showed adequate thermal stability and better tensile strength for commercial packaging. These coatings are removed by exposing to strong alkali solution at 90 °C and the recyclability potential of the paper is confirmed for reuse.

These renewable resourced and eco-friendly coating materials are found to be suitable alternative for paper packaging and other coating applications with circular economy approach.

The study has been published in Progress in Organic Coatings, Volume 158, September 2021.

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