Wet Cellulose Research Articles

Evolution of the Pd0/PdO phase change on Pd-MCM-41 catalyst for efficient production of furfural from the fast pyrolysis of cellulose

Furfural (C5H4O2) is a high-value platform chemical that is traditionally derived from the solvolysis of hemicellulose. However, its production from pyrolysis is far from satisfactory. In particular, the abundant cellulose within lignocellulosic biomass has yet to be successfully upgraded into furfural. Consequently, the overall yield of furfural from a lignocellulosic biomass is extremely low. Herein, we report a facile heterogeneous catalyst prepared from a simple impregnation of palladium (Pd) onto MCM-41 mesoporous silica. The catalyst demonstrated a remarkably high selectivity of ∼58.5% and yield of ∼32.5 wt% for furfural from the fast pyrolysis of wet cellulose. It was also confirmed to reach a selectivity of 65.4% and yield of 44.5 wt% for furfural from wet xylan, as well as a furfural yield of 23.9 wt% from wet sugarcane bagasse. All these values are superior to the literature reports. Through advanced characterisation including in-situ synchrotron high-temperature XRD and DRIFTS measurement, the loading of Pd in a tiny quantity of 1 mol% was confirmed to be sufficient in enhancing the surface hydrophilicity of the MCM-41 support, promoting the adsorption of reactants especially the formaldehyde group (HCHO), as well as the desorption of the target product furfural. In addition, Pd oxide (i.e., Pd2+O) was confirmed to be the catalytic active site. However, it was partly reduced into metallic Pd0 during the cellulose pyrolysis, due to the preferred reduction by adsorbed formaldehyde group and other reductants including H2 and CO in the vicinity of the PdO sites on the Pd-O-Si interface. Nevertheless, the catalyst was proven to retain the memory of its initial state after combustive regeneration in air, having oxidation state of Pd, particle size, and dispersion degree being reversed to its original construction. Accordingly, its activity remained stable upon cyclic testing. All these results demonstrate a high practical viability of this heterogenous catalyst for the valorisation of cellulose-rich biomass, an otherwise abundant crop waste across the world.

Stormwater runoff microplastics: Polymer types, particle size, and factors controlling loading rates

Stormwater runoff is a pathway of entry for microplastics (MPs, plastics <5 mm) into aquatic ecosystems. The objectives of this study were to determine MP size, morphology, chemical composition, and loading across urban storm events. Particles were extracted from stormwater samples collected at outfall locations using wet peroxide oxidation and cellulose digestion followed by analysis via attenuated total reflectance (ATR) FTIR. Concentrations observed were 0.99 ± 1.10 MP/L for 500–1000 μm and 0.41 ± 0.30 MP/L for the 1000–5000 μm size ranges. Seventeen different polymer types were observed. MP particle sizes measured using a FTIR-microscope camera indicated non-target size particles based on sieve-size classification, highlighting a potential source of error in studies reporting concentration by size class. A maximum MP load of 38.3 MP/m2 of upstream catchment was calculated. MP loadings had moderate correlations with both rainfall accumulation and intensity (Kendall τ = 0.54 and 0.42, respectively, both p ≤ 0.005). First flush (i.e. rapid wash-off of pollutants from watershed surfaces during rainfall early stages) was not always observed, and antecedent dry days were not correlated with MP abundance, likely due to the short dry periods between sampling events. Overall, the results presented provide data for risk assessment and mitigation strategies.

Valorization of waste paper sludge as a sustainable source for packaging applications

Paper sludge consists mainly of wet short cellulose fibers that are lost during papermaking and of residual chemicals used in the manufacturing process that remain dissolved in the water. Each ton of paper generates about 40–50 kg of dry sludge, of which 70% is primary sludge. Paper production, which exceeded 400 million tons globally in 2020, generates vast volumes of solid waste. Primary sludge is usually fiber-rich and hence suitable to be recycled back into the papermaking process. However, if the sludge is to be disposed of in landfills, sustainable practices must be developed in order to recover the fibers as they are valuable source for manufacturing high value-added products. This study investigates the valorization of paper sludge discarded by a filter paper manufacturer, with the purpose of producing cellulose acetate films for food packaging. The process involves recovering cellulose fibers from the sludge, purifying them and through acetylation reaction produce cellulose acetate films. FTIR spectra confirmed successful acetylation of fibers and also that acetyl groups reduced the hydrophilicity of cellulose—the contact angle was increased to over 80° from 50° in native cellulose. The films exhibited very good water barrier properties at both 50% and 90% relative humidity (RH).Graphical abstract

A wet bacterial cellulose film self-anchored by phosphotungstic acid: Flexible, quick-response and stable cycling performance for photochromic application

Bacterial cellulose (BC) has been recognized as an ideal supporter owning to its abundant hydroxyl groups on the surface. In this work, Keggin-type phosphotungstic acid (H3PW12O40, PWA) is self-anchored on the three-dimensional network of BC by a simple diffusion method at room-temperature. BC fibers can protect the well-dispersed PWA with high transparency, high mechanical strength, and high stability. When PWA/BC serves as a photochromic material, the coloration time and bleaching time are only 3 min and 30 min respectively. After 6 cycles, the photochromic ability of the PWA/BC composite film almost unchanged. At the same time, we convert the coloration and bleaching degree into quantitative data including a color difference calculation of ΔE2000 and the remaining degree of color (RC%). Within the BC system, PWA exhibits a special linear relationship between RC% and bleaching time (0–30 min). The processes of PWA/BC reduction (W6+→W5+) and oxidation (W5+→W6+) are analysed by photo-electrochromic, XPS and ESR characterizations. The revealed excellent photochromic properties of soft PWA/BC films highlight their potential as the photoresponsive materials.

Experimental studies of dynamic compression of cellulose pulp fibers

The ability to control the structure of the wood-pulp fiber cell wall is an attractive means to obtain increased accessibility to the fiber interior, providing routes for functionalization of the fibers that support further processing and novel material concepts, e.g. improved degree of polymerization, nanofiltration as demonstrated in previous studies. It has been proposed that dynamic compression and decompression of the cellulose pulp fibers in the wet state make it possible to modify the cell wall significantly.We hypothesize that hydrostatic pressure exerted on fibers fully submerged in water will increase the accessibility of the fiber wall by penetrating the fiber through weak spots in the cell wall. To pursue this, we have developed an experimental facility that can subject wet cellulose pulp samples to a pressure pulse ∼10 ms long and with a peak pressure of ∼300 MPa. The experiment is thus specifically designed to elucidate the effect of a rapid high-pressure pulse passing through the cellulose sample and enables studies of changes in structural properties over different size ranges. Different characterization techniques, including Scanning electron microscopy, X-ray diffraction, and wide- and small-angle X-ray scattering, have been used to evaluate the material exposed to pulsed pressure. The mechanism of pressure build-up is estimated computationally to complement the results. Key findings from the experiments consider a decrease in crystallinity and changes in the surface morphology of the cellulose sample.

DISPERSION OF CELLULOSIC MATERIALS BY AERODYNAMIC METHOD

The dissolution of primary and secondary cellulose semi-finished products in order to obtain a fluff fibrous product is becoming increasingly important due to the growth of its use in various industries. The existing equipment dissolves the dried semi-finished product, while the cellulose fibers partially lose their paper-forming properties. In the technology of aerodynamic forming of paper, a wet cellulose semi-finished product is dispersed, which preserves the ability of fibers to bond formation and excludes their mechanical destruction.&#x0D; Fluff pulp was obtained by dispersing dry and wet cellulose semi-finished product оn a laboratory installation for aerodynamic molding. The comparison of the properties of fibers by the value of their specific surface area and the ability to form paper with the strength characteristics required for operation is carried out. The breaking force value of paper formed from wet fibers is 4 times higher than that of paper from dry fibers.&#x0D; The possibility of using fluff pulp in the manufacture of multilayer paper for sanitary – hygienic purposes, which meets the requirements of GOST Ru 52354-2005 group B in terms of the values of the destructive force, is shown.&#x0D; The aerodynamic paper disperser can be used as an alternative equipment for separating cellulosic materials while screening the fibers.

High Output Direct-Current Nanogenerators Based on Charge Redistribution at Wet Cellulose/Metal Contact Interfaces

In the present work, a wet cellulose sponge-based direct-current electric generator (WCS-DCEG) is proposed, which offers a new power generation methodology for harvesting mechanical energy through an extremely simple structure. The device consists of two electrodes located on the surface of a dielectric substrate to collect direct-current output from the sliding motion of a wet cellulose sponge. Here, mechanical energy is converted into electrostatic energy by the triboelectric effect, and then, electrical energy is obtained due to the charging effect between two electrodes with different work functions. This is different from the traditional triboelectric nanogenerators which generate electricity through the electrostatic induction process. A single WCS-DCEG is capable to produce a current density of 75 μA/cm2 and an induced voltage of approximately 0.48–0.90 V with direct-current characteristics. The voltage and current outputs can be increased by synchronizing the outputs of multiple units of WCS-DCEG connecting in series or parallel. Additionally, WCS-DCEG proves a great accuracy for measuring the ion concentration in an aqueous solution ( R 2 = 0.996 ). These findings exhibit the great potential application of WCS-DCEG as an efficient strategy for harvesting mechanical energy and in the field of self-powered sensor fabrication.

High production of furfural by flash pyrolysis of C6 sugars and lignocellulose by Pd-PdO/ZnSO4 catalyst

Furfural (C5H4O2) is an important platform chemical for the synthesis of next-generation bio-fuels. Herein, we report a novel and reusable heterogeneous catalyst, Pd-PdO/ZnSO4 with 1.1 mol% palladium (Pd), for the production of furfural by flash pyrolysis of lignocelluloses at 400 °C. For both dry and wet C6 cellulose and its monomers, the furfural yields reach 74–82 mol%, relative to 96 mol% from C5 xylan and 23–33 wt% from sugarcane bagasse and corncob. The catalyst has a well-defined structure and bifunctional property, comprising a ZnSO4 support for the dehydration and isomerization of glucose, and a local core-shell configuration for metallic Pd0 encapsulated by an oxide (PdO) layer. The PdO layer is active for the Grob fragmentation of formaldehyde (HCHO) from glucose, which is subsequently in-situ steam reformed into syn-gas (i.e. H2 and CO), whereas the Pd0 core is active in promoting the last dehydration step for the formation of furfural.

Thermodynamics of enzymatic hydrolysis of cellulose

In this research, the thermodynamical analysis of the enzymatic hydrolysis of cellulose samples with different crystallinity has been performed. Calorimetric methods were used to determine the combustion enthalpies of cellulose samples and enthalpies their interaction with water. As a result, the standard formation enthalpies of dry and wet cellulose samples as well as of glucose solutions were calculated. In addition, also the standard entropies were found. Based on the obtained parameters, the thermodynamic functions of the hydrolysis reaction at the standard temperature (298 K) were calculated. It was established that the hydrolysis process of semi-crystalline cellulose samples is exothermic. Since reaction enthalpy is negative and the temperature-entropy factor is positive, the Gibbs potential of this process becomes negative, which contributes to the implementation of enzymatic hydrolysis of cellulose at standard temperature. Moderate enhancement in temperature to optimal value (323 K) increases the negative Gibbs potential and thereby promotes the hydrolysis of cellulose substrates. A correlation was found between the negative value of the Gibbs potential and the concentration of the resulting glucose solutions. It was also shown that the enzymatic hydrolysis of completely crystalline cellulose cannot be performed even at optimal temperature due to the zero value of the Gibbs potential.

РЕЗУЛЬТАТЫ ЗАЖИВЛЕНИЯ ОЖОГОВЫХ РАН С ПОМОЩЬЮ РАНЕВЫХ ПОКРЫТИЙ НА ОСНОВЕ БАКТЕРИАЛЬНОЙ ЦЕЛЛЮЛОЗЫ В ЭКСПЕРИМЕНТЕ

Purpose of the study: in experimental studies to evaluate the effectiveness of healing and changes in the microbial spectrum of deep burn wounds during their treatment using wound dressings based on bacterial cellulose. Materials and methods. The object of the experimental studies was 60 Wistar rats, which formed a deep skin burn. All animals were divided into 3 groups, of which in group 1 (n=20) burn wounds were treated with pure wet bacterial cellulose (BC) wound dressings, in group 2 (n=20) BC was used with exposure to a 1% chlorhexidine and in group 3 (n=20) traditional treatment was performed with Levomekol ointment. On days 5, 10, 15, 20, 28 in the groups, the area of the wound surfaces, the dynamics of their decrease, and the microbial spectrum were studied. Results and conclusions. We registered that wound dressings based on wet bacterial cellulose, applied in pure form and with exposure to an antiseptic (1% chlorhexidine solution) for 28 days, increase the healing rate of burn wounds by an average of 18% compared to the traditional treatment group. The formed scab over the wound, when BC dries, provides the wound surface with a mechanical protective barrier that prevents injury to emerging dermal cells, microbial contamination and thereby increases the rate of epithelialization in a closed environment.

Swelling-based gelation of wet cellulose nanopaper evaluated by single particle tracking

ABSTRACT Nanopapers fabricated from cellulose nanofibers (CNFs) drastically swell to form hydrogels when they are in contact with water. This gelation makes contrast with conventional papers that simply deform without drastic volume increase. While the volume increase is qualitatively obvious from the macroscopic visual inspection, its quantitative understanding is nontrivial because of the difficulty in the detection of the boundary between the nanopaper hydrogel and the residual or extra water. In this study, we use single particle tracking (SPT) to reveal the swelling-based gelation phenomenon of cellulose nanopapers. The diffusive dynamics of probe particles uncovers the transient process of swelling, and equilibrium analysis reveals the dependence of volume increase fundamentally dependent on the amount of water to be in contact with the nanopapers. Comparison with the aqueous CNF dispersion without drying reveals the difference in the texture of the nanopaper hydrogels from them.

A Study on the Reliability of Mass, Density, and Fire Performance of Recycled Wastepaper Building Finishing Material Made with Large Wet Cellulose 3D Printers

The impact of non-face-to-face contact following the COVID-19 pandemic has emerged as a social problem and has increased the amount of wastepaper, mainly in home delivery boxes. The appropriate recycling of paper waste is an area where sustainable growth is required in terms of the net environment system and carbon neutrality practice. Therefore, in this study, a specimen of building finishing material using wastepaper was produced using a custom-made large wet cellulose (LWC) 3D printer, and the site applicability of the fire performance was evaluated. The specimen of the building finish material was a mixture of wastepaper and ceramic binder, and the molding of the specimen was uniformly produced by a cylinder injection-type LWC 3D printer. The production reliability of the 3D printer was analyzed by measuring the mass and density of the specimen. The uniformity of the mass and density of the manufactured building finishes were confirmed to have standard deviations of ±0.05 g and ±0.01 g/cm3, respectively. The uniformity of the fire performance of specimens was confirmed by checking the relative standard deviation (RSD) value of ±3% under the same ceramic addition conditions from ISO 5660-1. Through the mass and density analysis and fire performance analysis of the building finishing materials, it was confirmed that the same mass, density, and fire performance can be produced simultaneously, and manufacturing using LWC 3D printers has been confirmed to be effective in developing uniform semi-non-combustible and retardant building materials.

Micro-patterned cellulose films for flexible electrodes in medical implants

Neuromodulation treatments are based on the functional interface between the brain and man-made electrodes. Chronic inflammation around the implant, however, occurs as a result of mechanical mismatching between soft brain tissue and the stiff metallic electrode. After water uptake, cellulose films should prevent encapsulation of the electrode. In this work, we reinforced cellulose films with silk fibre networks, improving tear strength by a factor of four to seven and maintaining flexibility, characterised by an elastic modulus between 100 and 200 MPa. Whereas sputtered gold on flat films exhibited restricted adhesion, micro-patterning guaranteed reasonable adhesion of nanometre-thin gold to cellulose substrates. Micro-patterned cellulose films coated in 80 nm-thin gold retained conductivity for strains as large as 30%, while sheet resistance increased by a factor of about 30. Fabrication of the biocompatible electrodes is efficient and compatible with large-scale production. • Wet cellulose films for soft neural implants show elastic modulus as low as 124 MPa. • Silk reinforcement improves tear strength and retain elasticity of cellulose films. • Microstructuring of cellulose films enhances adhesion of 20–80 nm gold. • Gold on micropatterned cellulose remains conductive up to 30% tensile strain.

The cross-linked bacterial cellulose impregnated with octenidine dihydrochloride-based antiseptic as an antibacterial dressing material for highly-exuding, infected wounds

The highly absorbent, antibacterial dressings with a sustained release of the antimicrobial are considered necessary measures to counteract chronic wound biofilm-based infections. This study aimed to analyze wet and dry bacterial cellulose (BC) materials, modified by chemical cross-linking, and impregnated with an antiseptic based on octenidine dihydrochloride (OCT) in the context of its antibiofilm/antibacterial activity, exudate absorption, and cytotoxicity. The native BC was obtained from cost-effective, ecological-friendly potato juice (leftover from the starch industry). The ability to absorb and retain OCT, exudate absorption capacity, the kinetics of OCT release as well as antibiofilm/antibacterial activity of modified BC materials against biofilm-forming and planktonic bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) were investigated. The performed analyses revealed that modified BC materials, thanks to their layered structure with numerous air spaces, were characterized by sustained exudate absorption and OCT release profile, which allowed them to exhibit high antimicrobial activity for up to 7 days, with a reduction of planktonic and biofilm cells of 84–100% and 69–93%, respectively. The modified BC materials showed also no cytotoxicity against fibroblast cell line L929 in vitro and were characterized by firm adhesion to the curved surfaces. These results indicate that cross-linked BC impregnated with OCT may be a particularly promising dressing material (obtained using sustainable processes), especially in the treatment of biofilm-infected, highly-exuding wounds.

The influence of using wet cellulose poultice on nanolime consolidation treatments applied on a limestone

Consolidation treatment with nanolime is a common conservation intervention which needs more research to enhance penetration and mechanical properties while also minimizing the undesired white veil on the surface which significantly alters the surface appearance. In this light, the application of a cellulose poultice soaked in distilled water over the treated surface with nanolime tries to prevent the formation of white hazes and to favour nanolime carbonation and penetration in the pore structure. However, the real influence of this practice on the consolidation effectiveness has never been studied yet and is not yet well understood. In order to provide more insights about its most suitable application method, in this study, we investigated the effectiveness of a wet cellulose poultice for two different nanolime consolidation treatments on a weathered limestone. Nanolime has been synthetized by anion exchange processes and dispersed in two mediums: i) water and ii) 50% v/v of water and alcohol. The influence of the poultice on the penetration and aesthetic properties has been studied by drilling resistance measurement, ultrasounds test, stereomicroscopy, measurements of roughness and static contact angle, spectrophotometry and scanning electron microscopy (superficial and cross sectioned samples). Additionally, consolidation effectiveness has been evaluated through the changes in apparent density, open porosity, porosity network in the outer 5 mm of the surface by mercury intrusion porosimetry and surface cohesion by the peeling test. Results show that, contrary to what is usually assumed, samples where a wet cellulose poultice was applied after the consolidant reached the lowest penetration levels and retained lower dry matter in comparison to their counterparts without poultice. A consolidation treatment with nanolime is more complex that it is generally considered, and the application of poultices is not always enhancing consolidation level; the most suitable application procedure must be chosen with regards to the nanolime and substrate specific characteristics.

A Study on the Flame-Retardant Performance of Recycled Paper Building Materials Manufactured by 3D Printer

The increase in non-face-to-face lifestyles due to COVID-19 worldwide have shown an increase in delivery services. The number of parcels in 2020 was 3.373 billion, an increase of 20.9% from 2.788 billion in 2019. This phenomenon increased delivery box waste. Against this background, this study attempted to develop building materials from the recycling of delivery boxes. In this study, the self-developed WC (wet cellulose) 3D printer confirmed the standardization and uniform performance of the sample by filling the material supply cylinder with cellulose filaments and spraying the composite material through a 10 mm nozzle. The cellulose filament for a WC 3D printer is based on cellulose extracted from wastepaper, and a cellulose filament composite material is used by mixing additives. After manufacturing a specimen using the WC 3D printer, a reliability test for the flame-retardant performance of the material was conducted according to the ISO 11925-2 test method. As a result of the experiment, flame-retardant performance was confirmed at a 40 wt% or greater ceramic binder content. In addition, the WC 3D printer achieved accurate test results by producing specimens with uniform physical properties. In addition, we confirmed that 3D-printed WC can be used to develop customized building materials that can prevent fire spread.

Features of water vapor sorption by cellulose materials

In this research, the sorption of water vapor (WV) by various cellulose samples (microcrystalline cellulose, cotton cellulose, Kraft pulp, mercerized cellulose, and rayon fibers) has been studied. The sorption isotherms of WV for various samples have a sigmoid shape. To describe such isotherms, various models have been proposed, including mono- and multimolecular adsorption, formation of hydrates and solid solutions, as well as mixed models combining various sorption mechanisms. After critical analysis of known models, the improved absorption model was proposed to explain the interaction of VW with cellulose samples. It was confirmed that crystallites are inaccessible for water, and therefore water molecules can be trapped only by polar groups of non-crystalline (amorphous) domains of cellulose materials. The developed model permitted obtaining the general absorption isotherm of water molecules in amorphous domains of cellulose. Moreover, the equation was derived, which describes both the general isotherm and isotherm of any semi-crystalline cellulose sample, when its crystallinity or amorphicity degree was pre-determined. Based on the proposed absorption model, various characteristics can be found, e.g., degrees of amorphicity and crystallinity, the maximum amount of absorbed water, the specific surface area of wet cellulose sample, the amount of capillary condensed water, etc.

Effect of Impregnated Phenolic Resins on the Cellulose Membrane for Polymeric Insulator

In this study, a cellulose membrane (CM) was chemically treated with phenolic (PF) resin to improve its performance as a polymeric insulator. The CM was prepared from kenaf pulp, and the PF was synthesized from oil palm empty fruit (EFB) fibre. Four different concentrations of synthesized PF resin (5, 10, 15, and 20 wt.%) were impregnated under wet or dry conditions. Thermal analysis of the phenolic cellulose membrane (PCM) showed that the samples had good chemical interaction and compatibility. The PF uptake in the wet phenolic cellulose membrane (PCMW) was higher than in the dry phenolic cellulose membrane (PCMD). During the PF uptake, the CM underwent solvent exchange and absorption in wet and dry membranes, respectively. This difference also affected the crosslinking of PCM samples via the formation of methylene bridges. Due to the PF treatment, the PCM showed lower water absorption than CM. The PF concentrations also affect the surface roughness and electrical properties of PCM samples. These findings prove that PCM can be used as a renewable and green polymer electrical insulator.

Silica-Bacterial Cellulose Composite Aerogel Fibers with Excellent Mechanical Properties from Sodium Silicate Precursor.

Forming fibers for fabric insulation is difficult using aerogels, which have excellent thermal insulation performance but poor mechanical properties. A previous study proposed a novel method that could effectively improve the mechanical properties of aerogels and make them into fibers for use in fabric insulation. In this study, composite aerogel fibers (CAFs) with excellent mechanical properties and thermal insulation performance were prepared using a streamlined method. The wet bacterial cellulose (BC) matrix without freeze-drying directly was immersed in an inorganic precursor (silicate) solution, followed by initiating in situ sol-gel reaction under the action of acidic catalyst after secondary shaping. Finally, after surface modification and ambient drying of the wet composite gel, CAFs were obtained. The CAFs prepared by the simplified method still had favorable mechanical properties (tensile strength of 4.5 MPa) and excellent thermal insulation properties under extreme conditions (220 °C and −60 °C). In particular, compared with previous work, the presented CAFs preparation process is simpler and more environmentally friendly. In addition, the experimental costs were reduced. Furthermore, the obtained CAFs had high specific surface area (671.3 m²/g), excellent hydrophobicity, and low density (≤0.154 g/cm3). This streamlined method was proposed to prepare aerogel fibers with excellent performance to meet the requirements of wearable applications.

Histochemical structure and tensile properties of birch cork cell walls

Tensile tests of birch cork were performed in the tangential direction. Birch cork in the wet state showed significantly higher extensibility than those in the dried state. The histochemical structure of birch cork was investigated by microscopic observation and spectroscopic analysis. Birch cork cell walls showed a two-layered structure and the inner material bordering cell wall. In transmission electron micrographs, osmium tetroxide stained the outer layer and inner material, whereas potassium permanganate stained the inner layer and inner material. After removal of suberin and lignin, only inner layer remained and Fourier-transformed infrared spectra showed the cellulose I pattern. Polarizing light micrographs indicated that molecular chains in the outer layer and inner material were oriented perpendicular to suberin lamination, whereas those in the inner layer showed longitudinal orientation. These results suggested that the outer layer and inner material mainly consist of suberin, whereas the inner layer and compound middle lamella consist of lignin, cellulose, and other polysaccharides. We hypothesized a hierarchical model of the birch cork cell wall. The lignified cell wall with helical arrangement of cellulose microfibrils is sandwiched between suberized outer layer and inner material. Cellulose microfibrils in the inner layer bear tensile loads. In the wet state, water and cellulose transfer tensile stress. In the dried state, this stress-transferal system functions poorly and fewer cells bear stress. Suberin in the outer layer and inner material may prevent absolute drying to maintain mechanical properties of the bark and to bear tensile stress caused by trunk diameter growth.