Incorporating a phase change material (PCM) into fibres allows the fabrication of smart textiles with thermo-regulating properties. Previously, such fibres have been made from thermoplastic polymers, usually petroleum-based and non-biodegradable, or from regenerated cellulose, such as viscose. Herein, strong fibres are developed from aqueous dispersions of nano-cellulose and dispersed microspheres with phase changing characteristics using a wet spinning technique employing a pH shift approach. Good distribution of the microspheres and proper compatibility with the cellulosic matrix was demonstrated by formulating the wax as a Pickering emulsion using cellulose nanocrystals (CNC) as stabilizing particles. The wax was subsequently incorporated into a dispersion of cellulose nanofibrils, the latter being responsible for the mechanical strength of the spun fibres. It was possible to produce fibres highly loaded with the microspheres (40 wt%) with a tenacity of 13 cN tex−1 (135 MPa). The fibres possessed good thermo-regulating features by absorbing and releasing heat without undergoing structural changes, while maintaining the PCM domain sizes intact. Finally, good washing fastness and PCM leak resistance were demonstrated, making the fibres suitable for thermo-regulative applications. Continuous fabrication of bio-based fibres with entrapped PCMs may find applications as reinforcements in composites or hybrid filaments. © 2023 The Authors

Energy-conversion devices based on the phenomenon of proton conduction, for example, polymer electrolyte membrane fuel cells (PEMFCs), require low cost and sustainable electrolytes with high ionic conductivity and good mechanical properties under anhydrous conditions and at temperatures up to 150 °C. Biopolymers possess an intrinsic thermomechanical stability but an insufficient proton conductivity in the dry state, which however may be imparted by a protic ionic liquid (PIL). This work presents the preparation and properties of composite membranes made of cellulose nanocrystals (CNCs) and a PIL. The membranes are thermally stable and display an ionic conductivity within the range 10-4-10-3 S/cm for temperatures between 120 and 160 °C. Moreover, the analysis of the biopolymer's apparent dimensions at nanoscale reveals a dependence of the CNCs' defects, twisting, and aggregation in the presence of the PIL. Preliminary tests using a simple fuel cell setup demonstrate a response of the membranes to the inlet of H2 gas, with a generation of electrical current. These findings provide a solid groundwork for further development and future studies of biopolymer/PIL electrolytes for energy applications. © 2021 The Authors.

Silica nanoparticles (SNPs) dissolve in alkaline media, which limits their use in certain applications. Here, we report a delayed dissolution of SNPs in strong alkali induced by zinc oxide (ZnO), an additive which also limits gelation of alkaline cellulose solutions. This allows incorporating high solid content of silica (30 wt%) in cellulose solutions with retention of their predominant viscous behavior long enough (ca. 180 min) to enable fiber wet spinning. We show that without addition of ZnO, silica dissolves completely, resulting in strong gelation of cellulose solutions that become unsuitable for wet spinning. With an increase of silica concentration, gelation of the solutions occurs faster. Employing ZnO, silica-rich regenerated cellulose fibers were successfully spun, possessing uniform cross sections and smooth surface structure without defects. These findings are useful in advancing the development of functional man-made cellulose fibers with incorporated silica, e.g., fibers with flame retardant or self-cleaning properties. © 2021 The Author(s)

The conservation of textiles is a challenge due to the often fast degradation that results from the acidity combined with a complex structure that requires remediation actions to be conducted at several length scales. Nanomaterials have lately been used for various purposes in the conservation of cultural heritage. The advantage with these materials is their high efficiency combined with a great control. Here, we provide an overview of the latest developments in terms of nanomaterials-based alternatives, namely inorganic nanoparticles and nanocellulose, to conventional methods for the strengthening and deacidification of cellulose-based materials. Then, using the case of iron-tannate dyed cotton, we show that conservation can only be addressed if the mechanical strengthening is preceded by a deacidification step. We used CaCO3 nanoparticles to neutralize the acidity, while the stabilisation was addressed by a combination of nanocellulose, and silica nanoparticles, to truly tackle the complexity of the hierarchical nature of cotton textiles. Silica nanoparticles enabled strengthening at the fibre scale by covering the fibre surface, while the nanocellulose acted at bigger length scales. The evaluation of the applied treatments, before and after an accelerated ageing, was assessed by tensile testing, the fibre structure by SEM and the apparent colour changes by colourimetric measurements.

Production of fibers from non-thermoplastic polymers, such as chitosan, usually requires dissolution with subsequent fiber formation, for instance via coagulation. Good fiber-forming properties enable simultaneous spinning of multiple fibers into a yarn, which is one of the prerequisites for process scalability. Here, we report a multifilament wet spinning process that eliminates the use of such volatile organic compounds as methanol and acetone, enhances fiber formation and allows producing continuous well separated chitosan fibers after drying. This is achieved by: (i) solidification of the extruded solution by alkali and sodium acetate in the coagulation bath and (ii) further stabilization of the fibers by adsorbing the anionic surfactant, sodium dodecyl sulfate. The obtained fibers have circular cross-section and smooth surface. We demonstrate that it is possible to increase fiber breaking tenacity and Young′s modulus by applying stretching (draw ratios up to 1.77) or by incorporating cellulose nanofibrils (CNF, up to 4 wt% based on chitosan) in the spinning solutions However, the limitation of increased viscosity when adding CNF is needed to be overcome for possible higher reinforcement effects. We demonstrate that fiber breaking tenacity, Young′s modulus and elongation at break can be enhanced even further by increasing the spin dope temperature from 22 °C to 60 °C, simultaneously with increasing the spin dope solids content to keep the same dope viscosity. The fibers with maximum breaking tenacity of ca. 10 cN tex-1 at an elongation at break of ca. 7.5% were obtained.

Development of sustainable biobased fibers is required to displace their fossil-based counterparts, e.g., in textile, nonwoven, or composite applications. Regenerated protein fibers have a potential in this regard if their mechanical properties are improved. Herein, we study for the first time the use of nanocellulose as reinforcement in regenerated protein fibers produced using wet spinning. The influence of cellulose nanocrystals (CNC) incorporated into regenerated casein fibers is examined in terms of mechanical and morphological properties. The influence of different conditions for fiber chemical cross-linking is also investigated. Incorporation of CNC (up to 37.5 wt %) into spin dopes results in a continuous increase of fiber Young's modulus (up to twofold) in the dry state. Both maximum and breaking tenacity of dry fibers are enhanced by CNC, with a maximum at 7.0-10.5 wt % of CNC. When testing after being wetted, both breaking tenacity and Young's modulus of the composite fibers decrease, likely due to weakening of hydrogen bonds between CNC in the presence of water. We also demonstrate that the presence of salt during chemical cross-linking is crucial to produce intact and separated fibers in the yarn.

Microfluidic fiber spinning is a promising technique for assembling cellulose nanomaterials into macroscopic fibers. However, its implementation requires upscalabe fabrication processes while maintaining high strength of the fibers, which could not be previously achieved. Herein, a continuous wet spinning process based on microfluidic flow focusing is developed to produce strong fibers from cellulose nanofibrils (CNFs) and nanocrystals (CNCs). Fibers with an average breaking tenacity as high as 29.5 cN tex−1 and Young's modulus of 1146 cN tex−1 are reported for the first time, produced from nonhighly purified CNF grades. Using the same developed method, wet spinning of fibers from CNCs is achieved for the first time, reaching an average Young's modulus of 1263 cN tex−1 and a breaking tenacity of 10.6 cN tex−1, thus exhibiting strength twice as high as that of common CNC films. A rather similar stiffness of CNC and CNF spun fibers may originate from similar degrees of alignment, as confirmed by wide-angle X-ray scattering (WAXS) and birefringence measurements, whereas lower strength may primarily arise from the shorter length of CNCs compared to that of CNFs. The benefit of CNCs is their higher solids content in the dopes. By combining both CNCs and CNFs, the fiber properties can be tuned.

Recent developments in paper and canvas conservation have seen the introduction of nanocellulose (NC) as a compatible treatment for the consolidation of historical cellulosic artifacts and manuscripts. However, as part of the assessment of these new materials for canvas consolidation, the adhesion of the consolidation treatment (which takes place between the applied material and the substrate) has not yet been evaluated, and as a result, it is poorly understood by both the scientific and conservation communities. After evaluating the potential of NC treatments for the consolidation of cotton painting canvas, we investigate a route to promote the interaction between the existing canvas and the nanocellulose treatment, which is in our case made of cellulose nanofibrils (CNF). This was carried out by introducing a cationic polymer, polyamidoamine-epichlorohydrin (PAAE), as an intermediate layer between the canvas and the CNF. The morphological, chemical, and mechanical evaluation of the canvas samples at different relative humidity (RH) levels demonstrated how the adhesion of the added PAAE layer is a dominant factor in the consolidation process. Improvement in the coating of canvas single fibers by the CNF, higher adhesion energy between the canvas fibers and the CNF treatment, and finally overall stronger canvas reinforcement were observed following the introduction of PAAE. However, an increase in mechanical response to moisture sorption and desorption was also observed for the PAAE-treated canvases. Overall, this study shows the complexity of such systems and, as such, the relevance of using a multiscale approach for their assessment.

Nanocellulose has been recently proposed as a novel consolidant for historical papers. Its use for painting canvas consolidation, however, remains unexplored. Here, we show for the first time how different nanocelluloses, namely mechanically isolated cellulose nanofibrils (CNF), carboxymethylated cellulose nanofibrils (CCNF) and cellulose nanocrystals (CNC), act as a bio-based alternative to synthetic resins and other conventional canvas consolidants. Importantly, we demonstrate that compared to some traditional consolidants, all tested nanocelluloses provided reinforcement in the adequate elongation regime. CCNF showed the best consolidation per added weight; however, it had to be handled at very low solids content compared to other nanocelluloses, exposing canvases to larger water volumes. CNC reinforced the least per added weight but could be used in more concentrated suspensions, giving the strongest consolidation after an equivalent number of coatings. CNF performed between CNC and CCNF. All nanocelluloses showed better consolidation than lining with synthetic adhesive (Beva 371) and linen canvas in the elongation region of interest. 

We here report three different approaches to prepare silica-polyelectrolyte complexes for mechanical strengthening of cotton fibers. In the first approach, polyvinylpyrrolidone (PVP) was used as a stabilizing polymer to delay the adsorption of a poly(quaternary ammonium) species, PQA (a copolymer of dimethylamine and epichlorohydrin), on the surface of silica. In the second approach cationic starch (CS), which is a branched polyelectrolyte, was used and the adsorption of CS resulted in formulations with good colloidal stability. The third approach was based on reduction of the charge density of silica to prevent PQA adsorption. Lowering the pH reduced the surface charge of the silica and enabled control of the adsorption. As a result, the aggregation was prevented and only a thin layer of polymer adsorbed. For all formulations a second polyelectrolyte, carboxymethyl cellulose (CMC) was subsequently adsorbed on the cationic polyelectrolyte layer. The silica/polyelectrolyte formulations were evaluated by dynamic light scattering (DLS). The obtained formulations were applied on model surfaces of degraded painting canvas. The performance of the silica particles coated either with one cationic polyelectrolyte and or with a layer of cationic polyelectrolyte followed by a layer of anionic polyelectrolyte were assessed by tensile testing and the morphology of the treated samples was investigated with SEM. The particles coated with a single cationic layer increased the maximum load at break by 29% at the cost of a reduction in strain. The particles coated with a double layer increased the maximum load to a lesser extent; however, higher values of strain were recorded. For all systems the mass uptake was limited to around 5 wt%.