Regulating the micro-nano structure of cellulose nanofibers reinforced polyvinyl alcohol composites for enhanced mechanical and barrier properties via one-pot wet milling

Herein, a one-pot method is proposed to manufacture recyclable polyvinyl alcohol/cellulose nanofibers composites with excellent mechanical and barrier performance through wet co-milling of the 2,2,6,6-tetramethylpiperidine-1-oxyl oxidized bamboo pulp in the polyvinyl alcohol aqueous solution. This strategy achieves ultrafine nano-fibrillation of cellulose pulp into nanofibers and their simultaneous homogenous distribution in the polyvinyl alcohol matrix, as evidenced by the homogenized structural morphology and enhanced interfacial interactions. With increased grinding degree, the cellulose fibers are gradually exfoliated and uniformly distributed in the polyvinyl alcohol matrix. The structure evolution of polyvinyl alcohol/cellulose composites during exfoliation and the structure-properties relationship are systematically analyzed. Consequently, the resultant polyvinyl alcohol/cellulose nanofibers composite films exhibit a ‘reinforced concrete’ structure with improved grain boundary strengthening effect, stress transfer capability and barrier properties. The elastic modulus, tensile strength and toughness of the polyvinyl alcohol/cellulose nanofibers composite films are significantly enhanced by 195.1%, 33.8% and 56.2% compared to those of pure polyvinyl alcohol film, respectively. The greatly reduced oxygen permeability coefficient demonstrates their great potential in food packaging. This research proposes a practical one-pot method for the fabrication and structure regulation of polyvinyl alcohol/cellulose nanofibers composites and provides valuable insights into their structure-property relationships.