All-cellulose nanocomposite films based on cellulose acetate and cellulose biocolloids by solution blow spinning

Over the last years, the potential of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) as fillers in polymers for mechanical reinforcement and extending the operation lifespan of materials is highlighted. Here, we investigate the inclusion of CNCs and CNFs with two distinct functional groups (TEMPO-oxidized, or solely having hydroxyl groups) as nanofillers into cellulose acetate films. Solution blow spinning has been utilized as a novel approach to fabricate composite materials from renewable carbon feedstocks, and the resulting structural, morphological and mechanical properties were evaluated. A maximum concentration of 5 wt% was found for CNCs while this was lower for CNFs, 2.5 wt%, to achieve uninterrupted processing of composite materials via SBS. All-cellulose composites showed differences in morphological features depending on the nanofiller type. Interestingly, a low loading of CNCs (1.5 wt%) increases the strength at break by 30%, while the inclusion of CNFs in a same amount deteriorates the mechanical properties. However, further increase to 2.5 wt% CNFs provides enhanced tensile strength and elastic modulus values. The largest improvements in elongation at break and strength at break is achieved with the inclusion of 2.5 wt% TEMPO-oxidized cellulose nanofibrils. Microscopic analysis after fracture reveals coral-like structured films,  providing a unique mechanical behavior. Overall, the results point out that TEMPO-oxidized CNFs are efficient reinforcements to fabricate renewable carbon-containing composite materials with improved mechanical performance. The proposed SBS processing offers a unique advantage in the fabrication of highly flexible cellulose-based films, eliminating the need for plasticizers or additional additives.

Graphical abstract