Large-Scale Manufacture of Recyclable Bioplastics from Renewable Cellulosic Biomass Derived from Softwood Kraft Pulp

Petrochemical plastic accumulated on earth has caused a great threat to the ecological environment. Recently, the cellulose film has been one of the most attractive candidates to replace petroleum-based plastics owing to its favorable biodegradability, optical transparency, and resource abundance. However, the general strategies (including vacuum filtration, solution casting, etc.) to fabricate cellulose films are usually time-consuming and difficult to industrialize. Moreover, these films still suffer from inferior stability against water and poor mechanical strength in a humid environment, which is insufficient for practical applications. Herein, we report a facile and large-scale preparation strategy to manufacture high-performance cellulose bioplastic films composed of chemically and physically dual-crosslinked carboxymethylated cellulose fibers (CMFs). Moreover, the whole preparation time was within only 1 h, superior to the most reported method. In this process, bleached softwood kraft pulp was carboxymethylated to form a homogeneous negatively charged CMF slurry that can further crosslink with the polyamide epichlorohydrin resin or aluminum sulfate [Al2(SO4)3] via the strong electrostatic interaction. The resulting CMF-based bioplastic shows a high mechanical strength (158.2 MPa), excellent water stability, and improved wet strength (20.7 MPa). Furthermore, the CMF-based bioplastic also exhibits both high optical transparency (89.4%) and haze feature (77.9%), good thermal stability, and easy recyclability by mechanical disintegration. This fast, scalable, and low-cost strategy involving the simple papermaking process provides a promising industrialization route to produce a strong, recyclable, and sustainable cellulosic bioplastic that can potentially replace petrochemical plastics in engineering and packaging implications.