All-natural, hydrophobic, strong paper straws based on biodegradable composite coatings

Plastic-coated paper straws are insufficient to solve the plastic pollution problem because microplastics are formed during their degradation. In this study, upgraded paper straws were prepared by coating with biodegradable sodium alginate/cellulose nanofiber/stearic acid (SA/CNF/STA) on the surface of paper without additional adhesives. The tensile strength of the paper was enhanced synergistically by the coated SA and CNF after cross-linking with Ca 2+ ions, reaching a maximum (26.46 MPa) when the mass ratio of SA to CNF was 4:1. The straws were prepared by spirally winding coated paper into tubes. Subsequent STA modification with different concentration (1–40%) improved the water stability of the paper straws. The paper straws exhibited excellent mechanical properties (including 13.45 MPa of flexural strength, 13.30 MPa of compressive strength) and hydrophobicity (103.67° of maximum water contact angle). After 130 days of soil burial, the paper straws were completely degraded. The comprehensive performance of prepared straws exceeds that of commercially available products in the same category, and they are safe and biodegradable. Paper straw in the work is in line with the concept of green and low-carbon development.