Constructing carboxymethyl cellulose-metal ion crosslinked networks in old corrugated recycled paper enhances its strength and wet stability.

Sustainable and low-cost old corrugated container (OCC) paper has been extensively employed in packaging materials for shipping and handling different products to substitute petroleum-based plastics. However, the poor mechanical strength and wet stability of OCC papers impede their general use. To solve these problems, we proposed constructing a dense carboxymethyl cellulose (CMC)-Mⁿ⁺ (Mⁿ⁺: Ca²⁺, Al³⁺) crosslinked network in the OCC papers' interior, allowing outstanding mechanical performance and waterproof. The resulting OCC-CMC-Al³⁺ paper demonstrated a superior tensile strength of 49.6 MPa and Young's modulus of 1.9 GPa, substantially higher than that of original OCC paper (tensile strength of 15 MPa, Young's modulus of 0.7 GPa) and comparable to commercial plastics. More significantly, the OCC-CMC-Al³⁺ paper demonstrated a superior wet strength of 13.0 MPa to the original OCC paper of 0.6 MPa. Additionally, the OCC-CMC-Al³⁺ paper exhibited excellent thermal stability, durability, and biodegradability. Generally, the biodegradable, strong, and water-resistant OCC-CMC-Al³⁺ paper is a potential and ecofriendly material for substituting nonbiodegradable plastics. [ABSTRACT FROM AUTHOR]