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

Biobased food packaging barrier materials have not yet achieved broad adoption because they often fail to meet key requirements such as water vapor resistance, flexibility, and cost. Petroleum based plastics therefore remain dominant despite their environmental impact, driving the search for renewable and biodegradable alternatives. Cellulose esters have emerged as promising candidates, yet links between ester composition, molecular water interactions, and macroscopic barrier performance remain limited. Films of six commercially available cellulose acetate butyrates (CABs) and one cellulose acetate propionate (CAP) were investigated regarding water interactions, barrier performance, biodegradability, and thermal behavior. Composition dependent differences in hydration were observed, with CAP showing higher humidity and liquid water uptake than CAB. In contrast, macroscopic barrier properties, including water vapor permeability and water absorption, were weakly influenced by ester composition and instead governed by film morphology and processing history. Thermal analysis indicated that calorimetric features observed during first heating reflect the hydrated state of the films rather than crystalline melting. Biodegradation experiments showed limited but measurable soil degradation dependent on substitution chemistry. Overall, substitution chemistry controls molecular water interactions, while morphology and processing dominate macroscopic barrier performance, supporting cellulose esters as candidates for next generation food packaging. Copyright

In this work, dialdehyde cellulose microfibrils (DA-CMFs) were reacted with O-substituted hydroxylamines, demonstrating an effective and versatile method for lateral functionalization of DA-CMFs using mild, aqueous reaction conditions. Depending on the conditions used, partial or complete substitution of the aldehydes could be achieved. The reaction was performed in the presence and absence of the reducing agent α-picoline borane (PB). DA-CMFs were reacted with O-(carboxymethyl) hydroxylamine (HAAA), and the adhesive properties of native and HAAA-conjugated DA-CMFs to fibres were studied. The adhesive properties were shown to depend on charge; while native DA-CMFs aggregate heavily in contact with the fibre surface, HAAA-conjugated DA-CMFs showed significantly improved adhesion. For a degree of substitution of 50% or higher, a sealed layer, without aggregates, could be observed using electron microscopy. Finally, a versatile protocol for co-insertion of HAAA (carboxylate) and aminooxy-PEG<inf>3</inf>-azide (hydroxylamine azide) was developed and demonstrated, with high yields of insertion. The modified DA-CMFs retained good adhesive properties to fibres, showing that the approach is general, and that the chemistry can be tuned depending on the target application

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. 

Cellulose nanofibrils (CNFs) have been proposed as reinforcement for thermoplastic polymers due to their potentially superior mechanical properties. However, it seems still uncertain how the reinforcement ability of CNFs compares to cheaper pulp fibres, and how the suspected potential of CNFs can be fully utilized in biocomposites. Therefore, this study presents a direct comparative investigation of kraft pulp fibres and their fibrillated materials as reinforcement of high- or low-density polyethylene. Besides the experimental investigations, the tensile properties of the corresponding biocomposites were predicted by using micromechanical analysis. It was shown that considering the same fraction of fibrous materials (pulp fibres vs CNFs), the experimental and modelling results revealed that the highest tensile strength was obtained from the pulp fibre-reinforced biocomposites. Regarding the CNFs-reinforced biocomposites, the compatibilizer content had to be up to 20 wt% to experimentally achieve the tensile strength predicted by the model. © 2023 The Author(s)

Three-dimensional (3D) printing is a useful technique that allows the creation of objects with complex structures by deposition of successive layers of material. These materials are often from fossil origin. However, efforts are being made to produce environmentally friendly materials for 3D printing. The addition of lignocellulosic fibres to a polymer matrix is one of the alternatives to replace, for instance, glass fibres in composites as reinforcing materials. The fields of biocomposites and 3D printing open innovative application areas for pulp fibres from the pulp and paper industry. In this work, biocomposites of poly(lactic acid) (PLA), poly(hydroxyalkanoate) (PHA) and kraft pulp fibres were prepared in order to find a suitable formulation for filaments for 3D printing. The effect of two different types of kraft fibres (bleached (B) and unbleached (U)) and of PHA on the mechanical and thermal properties of the biocomposites was assessed. The addition of 30% kraft fibres to PLA resulted in an increase of the tensile modulus from 3074 to ∼4800 MPa. In the case of biocomposites containing PHA (50% PLA/20% PHA/30% kraft) the increase in modulus was more moderate (PLA+PHA+U: 3838 MPa, and PLA+PHA+B: 3312 MPa). The tensile strength of PLA (66 MPa) increased to 77 MPa in PLA+kraft biocomposites, while a reduction in strength was observed for PLA+PHA+U (43 MPa) and PLA+PHA+B (32 MPa). Filaments prepared with PLA, PHA and bleached and unbleached pulp fibres showed similar printability of complex geometries, demonstrating that unbleached pulp fibres could also be utilized in the preparation of biocomposites with good mechanical performance and 3D printing properties. © 2022 The Author(s)

This review is the first part of a comprehensive review of hydrophobisation of lignocellulosic materials. The purpose of this review has been to compare physical hydrophobisation methods of lignocellulosic materials. We have compared molecular physical adsorption with plasma etching and grafting. Adsorption methods are facile and rely upon the simple mixing or coating of the substrate with the hydrophobing agent. However, none of the surfactant-based methods reviewed here reach contact angles above 90°, making them unsuitable for applications where a high degree of hydrophobisation is required. Nevertheless, surfactant based methods are well suited for compatibilising the lignocellulosic material with a hydrophobic matrix/polymer in cases where only a slight decrease in the hydrophilicity of the lignocellulosic substrate is required. On the other hand, wax- and lignin-based coatings can provide high hydrophobicity to the substrates. Plasma etching requires a more complex set-up but is relatively cheap. By physically etching the surface with or without the deposition of a hydrophobic coating, the material is rendered hydrophobic, reaching contact angles well above 120°. A major drawback of this method is the need for a plasma etching set-up, and some researchers co-deposit fluorine-based layers, which have a negative environmental impact. An alternative is plasma grafting, where single molecules are grafted on, initiated by radicals formed in the plasma. This method also requires a plasma set-up, but the vast majority of hydrophobic species can be grafted on. Examples include fatty acids, silanes and alkanes. Contact angles well above 110° are achieved by this method, and both fluorine and non-toxic species may be used for grafting. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).

Lignocellulosic materials with hydrophobic properties are of great interest for developing sustainable products that can be used in various applications such as packaging, water-repellent and self-cleaning materials, oil and water separation or as reinforcements in biocomposite materials. The hydroxyl functional groups present in cellulose provide the possibility to perform various chemical modifications to the cellulosic substrates that can increase their hydrophobicity. This review is the second part of a comprehensive review on hydrophobization of lignocellulosic materials and summarizes the recent advances in the chemical modification of such substrates. The methods described in this review can provide changes in the hydrophilicity of the materials that range from a small decrease in the initial hydrophilicity of the substrate (contact angles below 90°) to superhydrophobic properties (contact angles above 150°). Additional attention has been paid to whether the modification is limited to the surface of the substrate or if it occurs in the bulk of the material. We also discuss hydrophobized cellulose material applications in packing and oil/water purification. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s).

This review is the third part of a series of reviews on hydrophobization of lignocellulosic materials, a relevant topic nowadays, due to the need to replace fossil fuel-based materials. The review provides an overview of the hydrophobization of lignocellulosic materials by polymer adsorption, and both chemical and radiation-induced grafting of polymers. While adsorbed polymers are only attached to the surfaces by physical interactions, grafted polymers are chemically bonded to the materials. Radiation-induced grafting is typically the most environmentally friendly grafting technique, even though it provides little control on the polymer synthesis. On the other hand, controlled radical polymerization reactions are more complex but allow for the synthesis of polymers with elaborated architectures and well-defined properties. Overall, a wide range of contact angles can be obtained by polymer adsorption and grafting, from a slight increase in hydrophobicity to superhydrophobic properties. The choice of modification technique depends on the end-use of the modified material, but there is a clear trend towards the use of more environmentally friendly chemicals and processes and the grafting of polymers with complex structures. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).

Thermomechanical pulp (TMP) fibres can serve as renewable, cost-efficient and lightweight reinforcement for thermoplastic polymers such as poly(lactic acid) (PLA). The reinforcing ability of TMP fibres can be reduced due to various factors, e.g., insufficient dispersion of the fibres in the matrix material, fibre shortening under processing and poor surface interaction between fibres and matrix. A two-level factorial design was created and PLA together with TMP fibres and an industrial and recyclable side stream were processed in a twin-screw microcompounder accordingly. From the obtained biocomposites, dogbone specimens were injection-moulded. These specimens were tensile tested, and the compounding parameters statistically evaluated. Additionally, the analysis included the melt flow index (MFI), a dynamic mechanical analysis (DMA), scanning electron microscopy (SEM) and three-dimensional X-ray micro tomography (X- (Formula presented.) CT). The assessment provided insight into the microstructure that could affect the mechanical performance of the biocomposites. The temperature turned out to be the major influence factor on tensile strength and elongation, while no significant difference was quantified for the tensile modulus. A temperature of 180 °C, screw speed of 50 rpm and compounding time of 1 min turned out to be the optimal settings. © 2022 by the authors.