Blends of polylactic acid-based waxes and polybutylene succinate-graft-maleic anhydride for sustainable packaging applications

Wax-coated paper and corrugated boxes are widely used in the packaging industry for their enhanced resistance to water and oil. However, these coatings present significant challenges for recycling and are not readily biodegradable. Herein, we report the paper coating applications of recyclable waxes that were synthesized from commercial polylactic acid (PLA) and 2-(1-octadecanyl)succinic anhydride (ODSA-PLAn-ODSA, where the ‘n’ in PLAn denotes the number of lactide units) which were blended with the graft copolymer polybutylene succinate-graft-maleic anhydride (PBS-g-MAn, where the ‘n’ in MAn denotes the wt% of maleic anhydride (MA) that had been grafted onto the PBS backbone). PBS-g-MAn was used to improve the strength, toughness, and flexibility of the wax-coated paper, thus reducing its brittleness and tendency to form cracks. ODSA-PLAn-ODSA waxes and PBS-g-MAn were dissolved in an organic solvent and applied onto starch pre-coated paper substrates. Subsequently, the water resistance of these neat or blend-coated paper samples was established via Cobb 1800 measurements. Paper coated with wax alone was found to have a Cobb 1800 value of 28.3 ± 3.4 g/m², while the wax/graft copolymer blend-coated paper (coated with ODSA-PLA15-ODSA/PBS-g-MA5, with a 75:25 wax: graft copolymer weight ratio) exhibited a much lower Cobb1800 value of 3.7 ± 1.3 g/m². An excellent oil resistance (with the maximum possible kit rating of 12/12) was shown by all coated paper samples. The thermal sealing strength of the wax blend-coated paper was comparable to that of commercial acrylic-coated paper. Finally, the wax-blend coated paper successfully passed the standard repulpability and recyclability tests. These findings strengthen coated paper's position in sustainable packaging, as these coated papers are recyclable and have excellent water & oil resistance.