Old corrugated box (OCB)-based cellulose nanofiber-reinforced and citric acid-cross-linked TSP–guar gum composite film

Abstract

Old corrugated box (OCB) as a raw material was treated using alkali, acetic acid with NaClO and hydrogen peroxide to extract partially purified cellulose microfibers. FTIR and XRD analysis indicates the significant removal of non-cellulosic (lignin and hemicelluloses) content, followed by a notable increase in cellulose purity and crystallinity. Obtained cellulose microfibers (diameter 60–70 µm) were broken down to cellulose nanofibers (diameter up to 80 nm) using high-pressure homogenizer at 1700–1800 bar pressure consisting of 30 cycles and further characterized by SEM and XRD. Later on, nanocomposite films were prepared and optimized for required citric acid concentration for cross-linking with tamarind seed polysaccharide/guar gum blend by polycondensation reaction. And plasticized by glycerol (0.5% w/v) with different concentrations of OCB-CNF (0.1–1% w/v). The cross-link reaction was optimized at 80 °C for 3 h in order to confirm the esterification reaction between citric acid, polysaccharide and nanofiber. Increasing characteristic band intensity at around 1731 cm−1 represents ester bond formation is supported by the FTIR analysis. Rheology reveals the increase in cross-linking density after citric acid cross-link at 0.2% of OCB-CNF. Improvement in interfacial bonding between nanofiber and matrix results in enhanced tensile strength, barrier property and thermal stability as compared to those of control film. In addition, swelling behavior of OCB-CNF composite films was studied at different pH conditions (pH = 3, 7 and 10), where 0.2% and 0.5% OCB-CNFs showed better interaction with the matrix polysaccharide.