Simultaneously reinforce and de-color nanocellulose/lignin composite films by tuning hydroxyl groups with sodium borohydride

Researchers utilized NaBH4 to gently modify alkali lignin, resulting in L-Sx-ty-Pz with high hydroxyl value and decolorization, significantly enhancing the strength of composite films with cellulose nanofibers (CNF). Without strict pH control, the hydroxyl content of the modified lignin reached as high as 9.14 mmol/g. The CF/L-S1-t120-Pu composite film achieved a maximum stress of 45.33 MPa, representing a 116% and 77% increase compared to pure CNF and crude alkali lignin composite films, respectively. The reduction effect of NaBH4 imparted transparency to the film, broadening its applications. Additionally, the film's excellent antibacterial and flame-retardant properties provide strong support for industrial utilization.