Eco-Friendly Ethyl Cellulose Coating for Molded Kraft Paper Food Packaging with Multifunctional Barriers and Promising Recyclability

Abstract This study presents an eco-friendly, PFAS-free molded kraft paper bowl coated with ethyl cellulose (EC) to improve water, oil, and thermal resistance while retaining fiber-recovery potential. Kraft paper (K) was hot-press molded into bowls and dip-coated with EC solutions. Among the tested conditions, three cycles of 10 wt % EC (K/10EC-D3) produced a continuous coating (∼45 μm) with sufficient coverage over the three-dimensional molded geometry. The EC coating increased dry tensile strength by 25%, increased the water contact angle to 70°, reduced Cobb120 water absorptiveness to 2.46 g/m2, and achieved the highest grease resistance (Kit 12). Importantly, wet mechanical testing demonstrated that K/10EC-D3 retained substantially higher tensile strength and modulus after 30 min of water exposure at both 23 and 95 °C, confirming effective short-term protection against moisture-induced mechanical deterioration. Under simulated food-service conditions, the coated bowls maintained structural integrity during exposure to hot water, tea, oil, and greasy foods, as well as microwave heating and freeze–thaw–microwave cycling. Overall migration remained below the EU regulatory limit of 10 mg/dm2 for all tested food simulants. Laboratory-scale repulping and solvent-assisted washing enabled effective fiber recovery, with EC removal verified by FTIR and SEM. These findings demonstrate that EC dip coating can provide multifunctional barrier performance and short-term wet mechanical stability to three-dimensional molded kraft paper while maintaining promising fiber-recovery potential for sustainable PFAS-free food packaging.