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The surface chemistry and dispersion in poly(lactic-acid) of microfibrillated wood and microfibrillated lignocellulose prepared from untreated and partially delignified beech were compared with conventional microfibrillated cellulose produced from bleached pulp. High heterogeneity in fibril morphology and bulk chemical composition was observed. Also surface chemistry of the fibrils was highly variable, but not clearly correlated with bulk chemistry. Composite solution-cast films of poly(lacticacid) reinforced with 1 % fibrils were produced by adding fibrils dried from solvent into a polymer solution. Highly variable dispersion of fibrils correlated with varying mechanical performance was observed. Correlations were obtained between surface chemistry of fibrils as revealed by X-ray photoelectron spectroscopy and adhesion force microscopy on the one hand and the tensile performance of the fibril-reinforced polymer composites on the other hand. Overall, certain variants of fibrillated material with residual lignin and hemicellulose content showed reduced surface polarity, improved dispersion in poly(lactic-acid) and improved reinforcement efficiency compared to conventional MFC produced from bleached pulp.

This work established an energy-saving and straightforward treatment of cellulosic pulp to obtain functional cellulose nanofibers equipping them at the same time with catalytic activity and flame-retardant properties. For this purpose, dried cellulose pulp was mixed with a recyclable swelling agent, ZnCl 2 hydrate, at room temperature. The mild treatment affected the crystal structure through a partial amorphization, yielding a mix of native cellulose I and regenerated cellulose II. This treatment tremendously facilitated the fibrillation into a cellulose nanofiber (CNF) network. In comparison to fibrillated cellulose from nontreated pulp, the ZnCl 2 -treated counterpart featured higher viscosity, film transparency, better mechanical properties, and higher heat stability. Films produced from these nanofibers showed flame-retardant properties without any further modification. The ZnCl 2 −CNF showed also high reactivity in fiber surface acetylation and allowed a fast and efficient reaction while using very mild conditions. All in all, we propose a simple and resource-efficient cellulose treatment to obtain a nanostructured cellulose. These nanofibrils are decorated with ZnCl 2 which imposes flame-retardant properties and confined catalytic activity at the fibril surface.

Nowadays, environmental concerns make us rethink the way that we live and eat. In this regard, alternative protein sources are emerging; among them, insects are some of the most promising alternatives. Insect farming is still an infant industry, and to improve its profitability and environmental footprint, valorization of the byproducts will be a key step. Chitin as the main polysaccharide in the exoskeleton of insects has a great potential in this regard and can be processed into high value-added materials. In this study, we extracted and fibrillated chitin fibers from fly larvae (Hermetia illucens) and compared them with commercial chitin from shrimp shells. A mix of chitin and cellulose fibers was also extracted from mealworm farming waste. The purified chitinous fibers from different sources had similar chemical structures as shown by Fourier transform infrared and nuclear magnetic resonance spectroscopies. After mechanical fibrillation, the nanostructures of the different nanofibers were similar with heights between 9 and 11 nm. Chitin nanofibers (ChNFs) from fly larvae presented less nonfibrillated fiber bundles than the shrimp-derived analogue, pointing toward a lower recalcitrance of the fly larvae. ChNF suspensions underwent different film-forming protocols leading to films with tensile strengths of 83 ± 7 and 71 ± 4 MPa for ChNFs from shrimp and fly, respectively. While the effect of the chitin source on the mechanical properties of the films was demonstrated to be negligible, the presence of cellulose nanofibers closely mixed with ChNFs in the case of mealworm led to films twice as tough. Our results show for the first time the feasibility of producing ChNFs from insect industry byproducts with high potential for valorization and integral use of biomass.

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