The development of a cellulose nanofibrils film with permanent hydrophobicity using green processes, avoiding hazardous solvents, through easy procedures, is a great challenge. The hydrophobicity of a layer of calcium carbonate modified with stearic acid has already been presented. However, the combination of a cellulose nanofibrils film with a layer of modified calcium carbonate to develop a permanent hydrophobic cellulose-based material rises the additional issue of adhesion between layers. In the present study, a set of cellulose nanofibrils films was coated with a layer of stearic acid and another set was additionally covered with modified precipitated calcium carbonate (0.4–6 µm sized particles with above 50% aragonite crystalline form), previously modified with a stearic acid suspension using ultrasounds. To investigate the issue of adhesion between layers, some films were subjected to heat treatments at 68 and 105 °C. Structural and physical analysis of the films, as well as barrier properties and static/dynamic contact angle measurements were performed. Results show that overall mechanical performance of the films was not substantially affected by the coating and posterior heat treatments. Heat treatments decreased the water vapor transmission rate of stearic acid coated films from 91.9 to 31.6 g m⁻² day⁻¹and the oxygen permeability of stearic acid and modified calcium carbonate coated films from 26.4 to 2.6 cm³ µm/(m² day kPa). The double layered coated cellulose nanofibrils films attained contact angle hysteresis of 3.1° and 5° and static contact angles of 150° and 140° with no heat treatment and with a heat treatment of 68 °C, respectively. The heat treatment enabled to permanently adhere modified calcium carbonate particles on the film, providing it with persistent hydrophobicity.

Increasing concerns about environmental issues have recently intensified the search for sustainable alternatives to conventional plastics that minimize ecological impacts. This study evaluates the biodegradability, compostability, and ecotoxicity of a PLA-based biocomposite containing 30–40% micronized cellulose fibers. The material complied with the European limits for fluorine and heavy metals. Biodegradability was assessed through a respirometric test under thermophilic conditions, achieving 81% degradation in 155 days. Thermophilic compostability was evaluated by monitoring the disintegration of injected products made from the biocomposite pellets and cut into pieces with thicknesses of 1.0 mm and 2.1 mm, revealing that increased specific surface area prolongs composting time. Ecotoxicity was tested through seed germination and plant growth assays on barley, onion, sunflower, tomato, and wheat using the biocomposite mature compost mixed (25% and 50%) with a TÜV Austria certified soil. Results showed species-dependent effects: sunflower germination was enhanced, while other plants experienced slight growth delays. No severe phytotoxicity was observed, except for barley and wheat. Despite the proven biodegradability and compostability, the biocomposite product’s dimensions influence disintegration and decomposition rates. Furthermore, compost applications may have variable effects on plant development. These findings improved knowledge about sustainable materials performance, raising awareness about more responsible design, consumption, and disposal strategies.

Hardwood vessel elements generate problems in industrial uncoated wood-free printing paper operation, causing vessel picking and ink refusal. These problems are mitigated using mechanical refining at the cost of paper quality. Vessel enzymatic passivation, altering its adhesion to the fiber network and reducing its hydrophobicity is a way of improving paper quality. The object of this paper is to study how the enzymatic treatment by xylanase and by an enzymatic cocktail containing cellulases and laccases affect elemental chlorine free bleached Eucalyptus globulus vessel and fiber porosities, bulk, and surface chemical compositions. Thermoporosimetry revealed the vessel structure to be more porous, surface analysis showed its lower O/C ratio and bulk chemistry analysis its higher hemicellulose content. Enzymes had different effects on porosity, bulk and surface composition of fibers and vessels, affecting vessel adhesion and hydrophobicity. Vessel picking count decreased 76% for papers containing vessels treated with xylanase and 94% for the papers with vessels treated with the enzymatic cocktail. Fiber sheet samples had lower water contact angle (54.1º) than vessels rich sheets (63.7º), that reduced with xylanase (62.1º) and cocktail (58.4º). It is proposed that differences in vessel and fiber porosity structures affect the enzymatic attacks, eventually causing vessel passivation.

In this work, biocomposites of polylactic acid (PLA) and polypropylene (PP) with micronized cellulose (MC) were produced by mold injection and subjected to accelerated aging with ultraviolet (UV) radiation. The tests took place over 10 weeks, during which the produced specimens were exposed to a total of 1050 h of ultraviolet light. During the UV aging test, images were captured, and spectral reflectance and colorimetric measurements were carried out on the specimens exposed to UV and on specimens of the same materials kept in the dark (originals). As expected, only residual color differences were observed in the original specimens with values of ΔE*_ab always below 0.5. On the other hand, spectral reflectance and colorimetric changes were noticed over time in the specimens subjected to UV radiation. In particular, the values of ΔE*_ab increased over time and were found to be higher for PLA with MC compared to PP with MC. Values of ΔE*_ab = 4.7, 9.0, and 10.4 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PLA with MC, whereas ΔE*_ab = 4.5, 6.8, and 7.3 were obtained for weeks 1, 5, and 10, respectively, for the specimens of PP with MC. Therefore, it was found that the specimens of PLA with MC showed greater color fading compared to the specimens of PP with MC when subjected to UV exposure. In addition, it was also found in this work that besides the color differences noted in the tested specimens, those made of PP with MC also showed signs of surface damage.

In this work an evaluation of Macro Stickies was performed on thirteen different cellulose-based materials through image analysis. In particular, the materials that were evaluated consisted of different types/categories of papers/products produced by the industry, namely, molded cellulose products, unbleached kraft papers, barrier papers, one recycled paper, and a laminated paper package. The Macro Stickies Evaluation was carried out using an image analysis tool developed by our research group to perform this kind of work from now on. The results indicated that eight of the processed samples revealed low/residual contents of Macro Stickies, whereas the remaining five revealed higher amounts of Macro Stickies in their surfaces. Of the eight samples showing a low/residual Macro Stickies content, five of them belonged to the unbleached kraft papers category, with an area per mass of Macro Stickies ranging from 8.60 to 29.04 mm²/kg. However, the lowest case did not belong to this category, but to the molded cellulose products category with a value of 6.10 mm²/kg. Of the five samples showing higher amounts of Macro Stickies, the worst three cases were associated to one of the barrier papers, the recycled paper and the laminated paper, with an area per mass of Macro Stickies of 28,973.42, 6998.56, and 14,058.76 mm²/kg, respectively. Macro Stickies can assume different sizes, numbers and distributions depending on the characteristics and nature of each sample, and can be a great concern in the recycling of cellulose-based materials. In this sense, the proper assessment of Macro Stickies provides valuable information for the recycling sector to classify them in the products, and to anticipate which materials might give rise to potential stickies related problems in the recycling process.

The effect of different acid sulfite pretreatment conditions on released components in the hydrolysates and the pretreated solid residues’ response to enzymatic hydrolysis for Eucalyptus globulus chips was investigated. Sodium bisulfite (0–15%), and sulfuric acid (0–5%) were used to pretreat chips at 170 °C and 190 °C, for as long as 30 min. The hydrolysates were analyzed through high-performance liquid chromatography (HPLC) and spectrophotometry. Overall porosity and pores larger than 2.65 nm (size of a typical cellulase) on the solid residues were estimated using glucose and two dextrans with different hydrodynamic radii as probes. The external specific surface area was analyzed by dynamic light scattering. The solid residues underwent enzymatic hydrolysis with an enzymatic cocktail. Very high (84–95%) carbohydrate conversion was achieved for either an extensively delignified biomass or a biomass with very high content of sulfonated residual lignin (23.4%), since internal porosity enables enzymes accessibility. At least 5% sodium bisulfite and 1% sulfuric acid was required to attain a carbohydrate release above 90% in the enzymatic hydrolysis. Results suggest that the presence of sulfonated lignin does not impair the enzymatic hydrolysis rate and extent. The increase of pretreatment temperature had a positive effect mainly on the initial rate of carbohydrates release in the enzymatic hydrolysis. The increase of the wood material dimensions from pins to conventional chips significantly decreased the hemicellulose removal in acid sulfite pretreatment but had a small effect on the enzymatic yield.