Environmental concerns over plastic pollution have intensified the search for alternative materials for single-use products, such as trays for food packaging. Dry forming, using wood pulp fibres, is a promising technology for the fabrication of various single-use products. However, the fabrication of trays with relatively complex geometry is challenging. In this study, an approach is introduced where trays are pre-formed in tailored three-dimensional (3D) printed meshes with varying distances between the printed lines in the side walls (1.5 mm, 1.8 mm and 2.0 mm) and bottom (1.0 mm) of the trays. This was expected to facilitate the deposition of wood pulp fibres during formation of a given tray geometry and subsequently yield trays with adequate grammage and mechanical properties. The approach was tested with thermomechanical pulp (TMP) and chemi-thermomechanical pulp fibres (CTMP). Both fibres have similar chemical composition (carbohydrates and lignin), but differed with respect to the structural properties. TMP fibres revealed higher fraction of disrupted fibres and fibrils on the fibre surfaces. These characteristics increased the densification of the TMP trays during thermoforming and thus provided higher mechanical properties, compared with the corresponding CTMP trays. A tray demonstrator was developed, with tray depth of 50 mm and side wall angles of 65°. Thermopressed trays (pressure and temperature of 40 MPa and 200 °C, respectively) yielded strength and modulus of 1–10 MPa and 400–1600 MPa, respectively. The mechanical performance depended on the type of fibre (TMP or CTMP) and on the area of measurement in the trays (side walls or bottom)

This study explores whether masterbatch systems (MBs) can effectively incorporate high loadings of TMP fibers and clay fillers into polyolefins while maintaining or improving the mechanical, thermal, rheological, and water absorption properties of conventionally compounded composites. MBs containing 60–80 wt% TMP fibers and clay fillers in a high-density polyethylene (HDPE) carrier were produced and subsequently diluted to 30wt% filler. Mechanical, thermal, melt flow index, filler dispersion by SEM images, and water absorption properties of the resulting specimens were assessed and compared to a control (direct mix of components with 30wt% filler). Equivalent formulations using recycled polypropylene (rPP) were also prepared to assess the robustness of the MB strategy across different polyolefin matrices. SEM image analysis revealed a homogeneous dispersion in both the MB and the diluted systems, with distances between clay particles in the diluted samples most commonly ranging from 5 to 10 µm. Tensile strength, Young’s modulus, and elongation remained mostly unaffected or were improved by the dilution step, as confirmed by measurements compared to the control (tensile strength 27.8 ± 0.7 MPa, modulus 2583 ± 102 MPa, and elongation 3.1 ± 0.3%). Thermal properties were also consistent with the control, and diluted samples exhibited reduced variability in melt flow index values. The HDPE-based MB approach also performed consistently in rPP; the HDPE-based MB diluted with rPP exhibited higher water absorption (approx. 64% higher) compared to the rPP-based MB diluted with rPP. This behavior is likely attributed to reduced compatibility between the components (HDPE and rPP). Overall, the results demonstrate that the MB route enables efficient incorporation of TMP fibers and clay into polyolefins without compromising key material properties, offering a practical and scalable alternative to direct compounding

This study demonstrates an approach for incorporating cellulose nanofibrils (CNFs) into polyurethane (PU) using a solvent-free masterbatch consisting of 30% CNFs and 70% polyol, where the latter component functions as a carrier. This is the highest concentrated re-dispersible CNF-polyol system described to date. CNF addition produced strong shear-thinning behaviour, reduced the temperature sensitivity of viscosity, and maintained network integrity under conditions representative of PU curing. Power-law and Arrhenius modelling indicated that at low-to-medium shear rates the CNFs dominate rheological response, but the polyols rheological profile dominate at high shear rates when the fibrils occupy less space due to fluid flow alignment. Oscillatory tests showed increased elasticity and the transition from a viscous fluid toward gel-like behaviour at around 2% CNF loading. Cured CNF-PU composites exhibited increased stiffness, with microscopy revealing mechanically engaged fibrils within the fracture surfaces. Overall, CNFs provide an effective bio-based route to rheology modification PU systems, highlighting their potential in high-performance coatings and adhesives

Cellulose nanofibrils (CNFs) were incorporated into solvent-free epoxy resin using the masterbatch (MB) method to induce thixotropic rheology and provide reinforcement. This approach avoids irreversible agglomeration, which typically occurs when drying CNFs, and mitigates the inhalation risks associated with many common rheology agents in solvent-free epoxy applications. This study compares the rheological impacts of four CNF MBs containing 10%, 30%, 50%, and 70% CNF – representing the highest CNF dosages reported in solvent-free systems. The MB with 30% CNFs was further evaluated for its mechanical and hygroscopic properties in composites. The addition of 1% CNFs increased tensile strength by 98.5%, with no significant negative impact on impact strength, elasticity, or elongation. While the high viscosity obtained from CNF MBs can limit the use of CNFs in coatings to low dosages, the paste-like consistency attained at higher loadings may be advantageous for applications such as thermoset 3D printing, for which preliminary tests were conducted

This study focused on the performance evaluation of clay and thermomechanical pulp (TMP) fiber to reinforce low- and high-density polyethylene (LDPE and HDPE) biocomposites. A 23 factorial experiment was designed using two levels of clay, TMP fibers, and PE as variables. Mechanical properties, thermal behavior, melt flow index, and water absorption were evaluated. In HDPE, the partial replacement of TMP fiber with 10 wt% clay increased the melting point. Clay also reduced the main polymer degradation temperature in both matrices (LDPE and HDPE). The mechanical properties of the samples with 20 wt% fiber and 10 wt% clay were similar to or better than those containing 30 wt% TMP, that is, tensile strength and modulus of 34 and 2700 MPa, compared to 30 and 2400 MPa, respectively. Although the water absorption increased with the addition of TMP fiber and clay, the water absorption of the composite with 20 wt% TMP and 10 wt% clay was relatively low and similar to the biocomposite containing 30 wt% TMP, that is, 1.15 and 1.07% after 30 days, respectively. The comparable properties of biocomposites with 30 wt% TMP and biocomposites with 20 wt% TMP and 10 wt% clay demonstrate the potential of clay to reduce the cost of the final product. Highlights: Clay enhances the tensile modulus and strength, and reduces the color darkening, compared to TMP. TMP fibers and clay reduce the melt flow index, elongation, and impact toughness. TMP fibers and clay increase the melting point and reduce the degradation temperature. Reduction in production costs of biocomposites by adding inorganic clay filler. 

Wood-derived components (e.g. fibers, lignin, nanofibers) are widely studied to develop thermoplastic biocomposites with, for example, improved mechanical properties and reduced global warming potential. Manufacturing of biocomposite products includes compounding and conversion processes (e.g., extrusion, injection molding, and 3D printing). These processes apply mechanical forces and heat to melt thermoplastic polymers and form a given product. However, in some cases, compounding and conversion stages may generate emissions of volatile organic compounds (VOC) and/or ultrafine particles (UFP) and we must consider their effects on human health. Additionally, due to the nano-dimensions cellulose nanofibers are considered UFP. Therefore, its impacts on human health should be evaluated, especially when dried for biocomposite production. This review provides an overview of emissions generated in the production line of lignocellulose-based biocomposites, considering: wood preprocessing, extrusion, 3D printing, and injection moulding. Emissions of VOCs and UFP were considered, including the occupational exposure limits according to the current regulations and the potential health effects associated with such emissions 

Biomass-derived oligo- and polysaccharides may act as elicitors, i.e., bioactive molecules that trigger plant immune responses. This is particularly important to increase the resistance of plants to abiotic and biotic stresses. In this study, cellulose nanofibrils (CNF) gels were obtained by TEMPO-mediated oxidation of unbleached and bleached kraft pulps. The molecular structures were characterized with ESI and MALDI MS. Analysis of the fine sequences was achieved by MS and MS/MS of the water-soluble oligosaccharides obtained by acid hydrolysis of the CNF gels. The analysis revealed the presence of two families: one corresponding to homoglucuronic acid sequences and the other composed by alternating glucose and glucuronic acid units. The CNF gels, alone or with the addition of the water-soluble oligosaccharides, were tested on Chili pepper (Capsicum annuum). Based on the characterization of the gene expression with Next Generation Sequencing (NGS) of the C. annuum’s total messenger RNA, the differences in growth of the C. annuum seeds correlated well with the downregulation of the pathways regulating photosynthesis. A downregulation of the response to abiotic factors was detected, suggesting that these gels would improve the resistance of the C. annuum plants to abiotic stress due to, e.g., water deprivation and cold temperatures. 

Previous efforts to acetylate fibers and cellulose nanofibers (CNFs) are methodologically demanding and usually based on organic solvents catalyzed by acids. Hence, the purpose of this study was to introduce an improved method to acetylate unbleached (2 % and 5 % lignin) and bleached fibers (<1% lignin), and the corresponding CNFs, using a one-pot strategy in an aqueous alkaline medium. The lignin content in the pulp fibers (5 %) influenced the morphology of the corresponding fibrillated materials, i.e., increased secondary fines (92 %) and mean fibril area (36 %). Additionally, the pulps and CNFs (0 % and 5 % lignin content) were acetylated and compounded with high-density poly(ethylene) (HDPE). Acetylation improved the mechanical strength from 19 MPa (HDPE) to 30–40 MPa (when including acetylated fibers or CNFs). Finally, acetylation revealed a positive effect on melt-flow-index and elongation at break, and the water absorption of injection molded specimens was reduced to roughly 0.6 % after 10 days of testing. 

Single-use plastic products have been identified as an environmental challenge. When such products are not recycled, they may end up in nature and thus cause, e.g., marine littering. Thermoformed wood pulp fibre products are gaining more interest to replace fossil plastic products. However, beverage caps made of wood pulp fibres are challenging due to the hygroscopic nature of wood fibres, i.e., they absorb water, deform and loose functionality. Hence, the purpose of this study was to develop a fibre-based beverage cap that could replace plastic tethered cap systems. Both unbleached and bleached Kraft pulp and chemo-thermo-mechanical pulp (CTMP) fibres were tested in thermoforming trials, using tailor-made metal moulds. The results showed that Kraft pulp fibres formed denser structures, with more limited water absorption, compared to CTMP. The mechanical properties of thermoformed specimens were suitable for the application, i.e., the strength, modulus and elongation were between 32 and 36 MPa, 4–4.9 GPa and 1.6–1.9%, respectively, depending on the type of pulp fibre. Additionally, in order to secure that the caps were functional in relevant conditions in contact with liquids (water or milk), the caps were surface modified by silylation and esterification to increase the liquid barrier. The results indicate that surface esterification increased the contact angle to 95°. On the other hand, the surface-modified caps could not entirely limit the liquid absorption over longer periods of time (>∼1 h) when the caps were directly exposed to liquid. However, the liquid barrier was satisfactory when the products were exposed to increased relative humidity in refrigerated conditions (relative humidity >76% and temperature <7 °C). 

The aim of this study was to investigate new materials from organosolv fibers, organosolv lignin, kraft fibers, and their blends. The organosolv fibers showed reprecipitated lignin on the surface, a comparably low fiber length of 0.565 mm on average, and a high fines content of 82.3%. Handsheets were formed and thermopressed at 175 °C and 50 MPa, yielding dense materials (1050–1100 kg/m3) with properties different to that of regular paper products. The thermopressing of organosolv fibers alone produced materials with similar or better tensile strength (σb = 18.6 MPa) and stiffness (E* = 2.8 GPa) to the softwood Kraft reference pulp (σb = 14.8 MPa, E* = 1.8 GPa). The surface morphology was also smoother with fewer cavities. As a result, the thermopressed organosolv fibers exhibited higher hydrophobicity (contact angle > 95°) and had the lowest overall water uptake. Combinations of Kraft fibers with organosolv fibers or organosolv lignin showed reduced wetting and a higher density than the Kraft fibers alone. Furthermore, the addition of organosolv lignin to Kraft fibers greatly improved tensile stiffness and strength (σb = 23.8 MPa, E* = 10.5 GPa), likely due to the lignin acting as a binder to the fiber network. In conclusion, new thermopressed materials were developed and tested, which show promising potential for sustainable fiber materials with improved water resistance.