DES-ultrasonication processing for cellulose nanofiber and its compounding in biodegradable starch based packaging films through extrusion

A twin-screw extrusion processing has been developed for compounding the reinforced thermoplastic starch for food packing applications. The reinforcement material was developed from the bamboo pulp through green processing technique (hydrated deep eutectic solvent (DES) hydrolysis and continuous ultrasonication). Hydrolysis with 50 % DES provided an optimum yield of 83.34 % with a 20–40 nm particle size distribution. The starch compounded film with 5 % cellulose nanofiber achieved a tensile strength of 5.07 ± 0.15 MPa and was comparable to commercially available biodegradable starch-polybutylene adipate terephthalate film (5.77 ± 2.03 MPa). The reinforcement of nanofiber in starch decreases the melt flow index and hydrophilic nature with enhanced thermal stability by 27.64 %. The film achieved 11.6 g/m2/day water vapor transmission rate that addressed the shelf-life required for bio composite packing. Biodegradability studies for films confirm a 70–85 % degradation within 60 days. Antimicrobial studies confirm the non-inhibitory nature of the prepared biodegradable composites.