Design of biodegradable cellulose filtration material with high efficiency and breathability.

Using respiratory protective equipment is one of the relevant preventive measures for infectious diseases, including COVID-19, and for various occupational respiratory hazards. Because experienced discomfort may result in a decrease in the utilization of respirators, it is important to enhance the material properties to resolve suboptimal usage. We combined several technologies to produce a filtration material that met requirements set by a cross-disciplinary interview study on the usability of protective equipment.

Utilizing and Valorizing Oat and Barley Straw as an Alternative Source of Lignocellulosic Fibers.

The transition to sustainable, biodegradable, and recyclable materials requires new sources of cellulose fibers that are already used in large volumes by forest industries. Oat and barley straws provide interesting alternatives to wood fibers in lightweight material applications because of their similar chemical composition. Here we investigate processing and material forming concepts, which would enable strong fiber network structures for various applications.

Nanoscale Mechanism of Moisture-Induced Swelling in Wood Microfibril Bundles.

Understanding nanoscale moisture interactions is fundamental to most applications of wood, including cellulosic nanomaterials with tailored properties. By combining X-ray scattering experiments with molecular simulations and taking advantage of computed scattering, we studied the moisture-induced changes in cellulose microfibril bundles of softwood secondary cell walls. Our models reproduced the most important experimentally observed changes in diffraction peak locations and widths and gave new insights into their interpretation.

Lignin Inter-Diffusion Underlying Improved Mechanical Performance of Hot-Pressed Paper Webs.

Broader use of bio-based fibres in packaging becomes possible when the mechanical properties of fibre materials exceed those of conventional paperboard. Hot-pressing provides an efficient method to improve both the wet and dry strength of lignin-containing paper webs. Here we study varied pressing conditions for webs formed with thermomechanical pulp (TMP).

Combining scattering analysis and atomistic simulation of wood-water interactions.

Molecular-scale interactions between water and cellulose microfibril bundles in plant cell walls are not fully understood, despite their crucial role for many applications of plant biomass. Recent advances in X-ray and neutron scattering analysis allow more accurate interpretation of experimental data from wood cell walls. At the same time, microfibril bundles including hemicelluloses and water can be modelled at atomistic resolution.

Crossover from mean-field compression to collective phenomena in low-density foam-formed fiber material.

We study the compression of low-weight foam-formed materials made out of wood fibers. Initially the stress-strain behavior follows mean-field like response, related to the buckling of fiber segments as dictated by the random three-dimensional geometry. Our Acoustic Emission (AE) measurements correlate with the predicted number of segment bucklings for increasing strain.

Bubble Attachment to Cellulose and Silica Surfaces of Varied Surface Energies: Wetting Transition and Implications in Foam Forming.

To better understand the complex system of wet foams in the presence of cellulosic fibers, we investigate bubble-surface interactions by following the effects of surface hydrophobicity and surface tension on the contact angle of captive bubbles. Bubbles are brought into contact with model silica and cellulose surfaces immersed in solutions of a foaming surfactant (sodium dodecyl sulfate) of different concentrations. It is observed that bubble attachment is controlled by surface wetting, but a significant scatter in the behavior occurs near the transition from partial to complete wetting.

High Internal Phase Oil-in-Water Pickering Emulsions Stabilized by Chitin Nanofibrils: 3D Structuring and Solid Foam .

Chitin nanofibrils (NCh, ∼10 nm lateral size) were produced under conditions that were less severe compared to those for other biomass-derived nanomaterials and used to formulate high internal phase Pickering emulsions (HIPPEs). Pre-emulsification followed by continuous oil feeding facilitated a "scaffold" with high elasticity, which arrested droplet mobility and coarsening, achieving edible oil-in-water emulsions with internal phase volume fraction as high as 88%. The high stabilization ability of rodlike NCh originated from the restricted coarsening, droplet breakage and coalescence upon emulsion formation.

How Cellulose Nanofibrils Affect Bulk, Surface, and Foam Properties of Anionic Surfactant Solutions.

We study the generation and decay of aqueous foams stabilized by sodium dodecyl sulfate (SDS) in the presence of unmodified cellulose nanofibrils (CNF). Together with the rheology of aqueous suspensions containing CNF and SDS, the interfacial/colloidal interactions are determined by quartz crystal microgravimetry with dissipation monitoring, surface plasmon resonance, and isothermal titration calorimetry. The results are used to explain the properties of the air/water interface (interfacial activity and dilatational moduli determined from oscillating air bubbles) and of the bulk (steady-state flow, oscillatory shear, and capillary thinning).

Compression Strength Mechanisms of Low-Density Fibrous Materials.

In this work we challenge some earlier theoretical ideas on the strength of lightweight fiber materials by analyzing an extensive set of foam-formed fiber networks. The experimental samples included various different material densities and different types of natural and regenerated cellulose fibers. Characterization of the samples was performed by macroscopic mechanical testing, supported by simultaneous high-speed imaging of local deformations inside a fiber network.

Structural properties and foaming of plant cell wall polysaccharide dispersions.

Water suspensions of cellulose nanofibres with xylan, xyloglucan and pectin were studied for foaming and structural properties as a new means for food structuring. The dispersions were analysed with rheological measurements, microscopy and optical coherence tomography. A combination of xylan with TEMPO-oxidized nanocellulose produced a mixture with well-dispersed air bubbles, while the addition of pectin improved the elastic modulus, hardness and toughness of the structures.

Porous structure of fibre networks formed by a foaming process: a comparative study of different characterization techniques.

Recent developments in making fibre materials using the foam-forming technology have raised a need to characterize the porous structure at low material density. In order to find an effective choice among all structure-characterization methods, both two-dimensional and three-dimensional techniques were used to explore the porous structure of foam-formed samples made with two different types of cellulose fibre. These techniques included X-ray microtomography, scanning electron microscopy, light microscopy, direct surface imaging using a CCD camera and mercury intrusion porosimetry.

Drying of Pigment-Cellulose Nanofibril Substrates.

A new substrate containing cellulose nanofibrils and inorganic pigment particles has been developed for printed electronics applications. The studied composite structure contains 80% fillers and is mechanically stable and flexible. Before drying, the solids content can be as low as 20% due to the high water binding capacity of the cellulose nanofibrils.

Theoretical and experimental study on phase transitions and mass fluxes of supersaturated water vapor onto different insoluble flat surfaces.

The heterogeneous nucleation and condensation of water vapor onto three different surfaces (newsprint paper, Teflon, cellulose film) was studied theoretically and experimentally. The theoretical framework included the use of the classical theory of heterogeneous nucleation, diffusion theory corrected with transition regime correction factors, and the theory of heat transfer. Experiments were carried out using an environmental scanning electron microscope (ESEM).