A High-Temperature-Resilient All-Cellulose Barrier for Next-Generation Beverage Packaging

Designing recyclable, polymer-free hot-beverage containers is essential for addressing the end-of-life challenges associated with polyethylene-lined paper cups and reducing reliance on fossil-derived barrier materials. In this work, we have developed a fully cellulosic barrier coating by reinforcing cellulose acetate (CA) with cellulose nanocrystals (CNCs) and applying the formulation onto porous paper substrates using a sealed, shear-free dispersion and blade-coating process. The resulting coatings form continuous, defect-suppressing surface layers that bridge macropores and partially integrate with the upper fiber network. Spectroscopic analysis confirms physical blending accompanied by hydrogen-bonding-mediated interfacial interactions between CA, CNCs, and the paper matrix, while Raman spectroscopy further reveals characteristic shifts consistent with enhanced bonding and chemical compatibility at the coating–substrate interface. Thermogravimetric measurements show delayed main-chain degradation and increased char yields with CNC incorporation, whereas electron microscopy reveals progressive surface densification and fiber-matrix interlocking. These structural improvements translate into monotonic gains in tensile strength and modulus, peaking at 5 wt % CNC, with enhanced toughness up to 3 wt % CNC. The coatings maintain integrity during a five-day immersion in protic/aprotic and acidic/basic media, exhibiting no film lift-off or channel formation. Oxygen transmission decreases by more than an order of magnitude relative to uncoated paper with CA alone and reaches low-permeability regimes when reinforced with CNCs. Under extended abrasion testing, commercial polyethylene-lined cups display progressive pitting, boundary opening, and flake-like surface degradation, whereas the CNC-CA surface remains cohesive, adherent, and low-defect, indicating superior resistance to abrasion-induced damage. These findings demonstrate a viable, high-performance fully cellulosic barrier coating that enables recyclable, polymer-liner-free hot-beverage packaging while providing strong mechanical, thermal, solvent-resistance, and gas-barrier performance compatible with a circular materials economy.