Toward millimeter thick cellulose nanofiber/epoxy laminates with good transparency and high flexural strength.

While cellulose nanofiber-based bioplastics are of great interest for replacing synthetic polymer and glass materials, the main limitation is their low thickness, which makes them difficult for various applications. In this study, we fabricated millimeter-scale thick bioplastic composites, based on 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (TEMPO-CNF) and epoxy resin, via sequential lamination processes. The glycerol as softener was added to TEMPO-CNF dispersion to prepare a thick TEMPO-CNF layer without shrinkage. It was discovered that the total thickness of TEMPO-CNF/epoxy laminates can be easily controlled by changing the thickness and number of TEMPO-CNF layers and the total thickness can also be easily increased up to 2.4 mm. Furthermore, these TEMPO-CNF/epoxy laminates have high flexural strength (272 MPa) as well as good transmittance (85% % at 600 nm). We anticipate that our approach will significantly broaden the strategies for fabricating nanocellulose-based bioplastics for use as a replacement for transparent synthetic polymers and glass materials.

Double-crosslinked cellulose nanofiber based bioplastic films for practical applications.

While green bioplastic based on carbohydrate polymers have showed considerable promise, the methods typically used to prepare them in a single material have remained a significant challenge. In this study, a simple approach is proposed to fabricate high performance cellulose films composed of chemically and physically dual-crosslinked 2,2,6,6-tetramethylpiperidine-1-oxy-oxidized cellulose nanofibers (DC TEMPO-CNFs). The hydroxyl groups of TEMPO-CNF suspensions were firstly crosslinked chemically with epichlorohydrin (ECH), and subsequently TEMPO-CNF matrices were crosslinked physically via the strong electrostatic interaction between carboxylate and Ca2+ ions. It was found that the optimized DC TEMPO-CNF films exhibit a good transmittance (90 %) and a high tensile strength (303 MPa). Furthermore, these DC TEMPO-CNF films revealed superior thermal stability and excellent water resistance compared to neat TEMPO-CNF films without crosslinked domains. We believe that these results will pave the way to preparing practical polysaccharide bioplastics with simple, environmentally-friendly manufacturing processes.

High-yield production of biosugars from Gracilaria verrucosa by acid and enzymatic hydrolysis processes.

Gracilaria verrucosa, the red alga, is a suitable feedstock for biosugar production. This study analyzes biosugar production by the hydrolysis of G. verrucosa conducted under various conditions (i.e., various acid concentrations, substrate concentrations, reaction times, and enzyme dosages). The acid hydrolysates of G. verrucosa yielded a total of 7.47g/L (37.4%) and 10.63g/L (21.26%) of reducing sugars under optimal small (30mL) and large laboratory-scale (1L) hydrolysis processes, respectively. Reducing sugar obtained from acid and enzymatic hydrolysates were 10% higher, with minimum by-products, than those reported in other studies. The mass balance for the small laboratory-scale process showed that the acid and enzymatic hydrolysates had a carbohydrate conversion of 57.2%. The mass balance approach to the entire hydrolysis process of red seaweed for biosugar production can be applied to other saccharification processes.