ALBERT

Description: We present a high resolution, ultra-frugal printing of paper microfluidic devices using in-house paraffin formulation on a simple filter paper. The patterns printed using an office inkjet printer formed a selective hydrophobic barrier of 4 ± 1 µm thickness with a hydrophilic channel width of 275 µm. These printed patterns effectively confine common aqueous solutions and solvents, which was verified by solvent compatibility studies. SEM analysis reveals that the solvent confinement is due to pore blockage in the filter paper. The fabricated paper-based device was validated for qualitative assessment of Candida albicans (pathogenic fungi) by using a combination of L-proline β-naphthylamide as the substrate and cinnamaldehyde as an indicator. Our studies reveal that the pathogenic fungi can be detected within 10 min with the limit of detection (LOD) of 0.86 × 106 cfu/mL. Owing to its simplicity, this facile method shows high potential and can be scaled up for developing robust paper-based devices for biomarker detection in resource-limited settings. Graphic abstract

Description: Vibratory ball milling of cotton in the presence and absence of styrene was studied by electron paramagnetic resonance spectroscopy, gel permeation chromatography and ultraviolet resonance Raman (UVRR) spectroscopy. Mechanoradical formation in ball milling of cellulose was detected, but the radical content was significantly lower and the molar mass slightly higher in the presence of styrene. UVRR also showed a small but consistent increase in aromatic signal, even after 5 h acetone extraction. A small portion of styrene was attached to cellulose, which was observed as an increase in the aromatic band intensity. Stabilization or a slight increase in molar mass of the samples that were milled in the presence of styrene was also observed. Overall, under the studied conditions, ball milling is not sufficient to significantly polymerize styrene onto cellulose. For future trials of mechanochemical copolymerization, it is recommended that a vacuum or an inert atmosphere be used.

Description: This paper reports on a spectrophotometric method for rapidly determining the reactivity of dissolving pulps. After mercerization and xanthation, the dissolved cellulose fractions in the viscose dope were re-precipitated by acidification. This transmittance/absorbance of fibril suspension was measured by visible spectroscopy, showing a strong linear correlation (R 2  = 0.997) between the absorbance at 600 nm and the amount of the regenerated cellulose in the sample; i.e., the pulp reactivity. The results measured by the present method and those of the commonly used modified Fock method were in good agreement, with a relative difference of less than 11 %. In summary, the new method is rapid, simple, practical and suitable for use in determining the reactivity of dissolving pulps in laboratory or industrial applications.

Description: In this study, the effect of high residual lignin (21 % w/w) on the thermal properties of cellulose nanofibrils and the performance of films made from these nanofibrils in aqueous environments have been explored for the first time. Individualised cellulose nanofibrils with diameter 〈100 nm were obtained from the mechanical fibrillation of bark residue fibers with high lignin content. The mass loss by thermal degradation started at a higher temperature of 306 °C for these nanofibrils compared to 278 °C for those fibrils with low amount of lignin (5 % w/w). The maximum rate of degradation occurred at a temperature of around 390 and 319 °C for high and low lignin containing nanofibrils, respectively. Such a high thermal stability for high lignin containing nanofibrils has never been reported for nanocellulose from any other studies. The films made from these high lignin nanofibrils showed lower water uptake and better wet mechanical properties compared to films made from low lignin containing cellulose nanofibrils. The high lignin nanofibril films retained 38 % of the dry strength properties, while the low lignin nanofibril films were able to retain only 9 % of dry strength.

Description: The aim of this paper is to contribute to an improved understanding of deformation mechanisms of paperboard in the deep drawing process with immediate compression which reaches the highest degree of formability. Experiments with different fiber types and material structures were conducted on a laboratory and pilot scale to determine the major material-related influences on the formability of paperboard. The different fiber type combinations were studied together with different additives. The results show that increased pore volume and fiber-to-fiber mobility significantly increase initial wrinkle height which is significant for the quality of the drawn three dimensional (3D) structure. A material structure consisting of a mixture of cellulose fibers and a low percentage of stiff regenerated cellulose or synthetic staple fibers in combination with alkyl ketene dimer or cationic wax as an additive leads to a wrinkle-free wall until a forming ratio (forming height divided by base diameter) of at least 0.22 is reached. Accordingly, the process can be broken down into three phases. In the first phase, the cellulosic structures are deformed or broken, and the material density is reduced due to fiber-to-fiber movement. Refining and wet pressing decrease pore volume, increase the number of bonds in the material, thereby obstructing fiber-to-fiber movement. In the second phase, wrinkles occur. The introduced bending stiffness index together with the tensile index provides an indication of the material behavior in these two phases. The third phase is a restructuring of the material structure and a fixation of wrinkles by creating new bonds in the limited wrinkle areas. The experiments indicate that refined fibers make significantly higher wrinkle strength possible and thus better fixation of the final 3D structure shape. Additives with low melting temperatures can also contribute to improved wrinkle strength even in a low mass percentage of 0.5 %.

Description: Cellulose chemical robustness still remains a burden for value-added compounds production from biomass. The goal of this study was to take profit of the synergetic effects of dilute acid treatment and microwaves for the hydrolysis of highly crystalline cellulose. Afterwards, the liquid phase obtained after this treatment was treated microbiologically to transform the hydrolyzed product, containing glucose, into lactic acid. The hydrolysis reaction was performed in a microwave reactor. The samples were irradiated for 30 min up to 4 h at 400 watts maintaining the temperature at 393 K. At the optimal conditions, 88 % of cellulose was hydrolyzed. Glucose was the main obtained product. Through bio-fermentation Lactobacillus delbrueckii converted selectively all the present glucose into 98 % optically pure d -lactic acid, without suffering any inhibition from the rest of hydrolyzed products. The combination of cellulose hydrolysis under microwave irradiation and bio-fermentation at the conditions performed in this study opens a new alternative route to obtain valuable chemical platform products from cellulose.

Description: Cellulose nanowhiskers (CNWs) prepared via TEMPO mediated oxidation are used as biodegradable filler in an epoxy matrix. Since CNWs are hydrophilic and epoxy is hydrophobic, amphiphilic block copolymer surfactants are employed to improve the interactions between the filler and the matrix. The surfactants used are Pluronics, a family of triblock copolymers containing two poly(ethylene oxide) blocks and one poly(propylene oxide) block. In this study, Pluronic L61 and L121 with molecular weight of 2000 and 4400 g/mol and hydrophilic to lipophilic balance of 3 and 1 respectively, are used and their effect on the dispersion of CNWs in epoxy is discussed. The hydrophilic tails of Pluronics interact with the hydroxyl and carboxylic groups on the CNW surface and then these surfactant-treated CNWs are directly incorporated into epoxy by high speed mixing. The dispersion state of the surfactant-treated CNWs in epoxy is assessed by rheological measurements and the mechanical properties of the resulting composites are characterized by tensile test and dynamic mechanical thermal analysis. The Pluronic L61 treated CNW/epoxy composites show the highest storage modulus at high temperatures (about 77 % increases) indicative of improved interfacial interactions between the CNWs and the epoxy matrix. Also, an increase of around 10 °C in the glass–rubbery transition temperature of the L61 treated CNW/epoxy composite leads to potential application at higher service temperatures.

Description: Polypyrrole/cellulose fiber-conductive composites were chemically synthesized in situ by using, for the first time, cationic polyacrylate copolymer as dopant and FeCl 3 as oxidant. The impacts of dopant charge density on the adsorption of the dopant on cellulose fiber, microstructure, tensile strength, conductivity and stability were investigated. In addition, the elemental composition, distribution and doping state of the polypyrrole in conductive fiber were determined by elemental analysis and X-ray photoelectron spectroscopy. Compared with anthraquinone-2-sulfonic acid sodium salt, cationic polyacrylate copolymer was a more effective dopant in increasing the conductivity and conductivity stability of conductive paper. The decay of mechanical properties was also weakened. The surface resistivity decreased from 4.6 to 0.3 KΩ square −1 with increasing dopant charge density from 0.525 to 0.820 μmol g −1 and then increased with a further increase in the dopant charge density. It was also found that the polypyrrole retention in conductive fiber reached the maximum when the charge density of the dopant was 0.820 μmol g −1 . When the conductive fiber was doped with high-charged dopant, polypyrrole was easier to enter into the fiber lumen, and bipoloran charge carriers were more easily formed. With respect to the conductive fibers prepared with dopant of 0.820 and 0.525 μmol g −1 charge density, the total content of polaron and bipolaron in the former conductive fiber was higher than the content of polaron in the latter conductive fiber. In addition, uniform and denser nanofibrous PPy can be formed by controlling the dopant charge density.

Description: The hybrid nanocomposite material of bacterial cellulose (BC) nanofibers and titaniumdioxide (TiO 2 ) nanoparticles with improved visible light sensitivity was developed by doping nitrogen (N) and fluorine (F) on TiO 2 nanoparticles embedded on BC nanofibers. To synthesize TiO 2 nanoparticles on BC produced by Acetobacter xylinum (TISTR 975), titanium tetraisopropoxide (TTIP) was used as a titanium source and was directly hydrolyzed on BC nanofibers. After providing heat via the reflux technique to BC/TiO 2 pellicle, the crystalline structure of TiO 2 was changed to an anatase form on a three dimensional network structure of BC confirmed by XRD. Nitrogen (N) and fluorine (F) were successfully doped into TiO 2 nanoparticles by using NH 4 F as the source of N and F (BC/N–F-co-doped TiO 2 ). The TEM results showed that the average particle size of BC/N–F-co-doped TiO 2 was smaller than the BC matrix containing none of the co-doped TiO 2 (BC/TiO 2 ) and N-doped TiO 2 (BC/N–TiO 2 ). In addition, BC/N–F-co-doped TiO 2 demonstrated the high efficiency of photocatalytic disinfection activity against both gram-negative and gram-positive bacteria under fluorescence light. Nevertheless, the photocatalytic antibacterial activity of N–F-co-doped TiO 2 also depended on the type of bacteria, and degree of N–F-co-doped TiO 2 .

Description: The interaction of copper ions with chitosan and three synthesized derivatives with different chelating centers, N -benzylidene chitosan, N -benzyl chitosan and poly- N -(4-(4- R -methoxyphenyl)diazenyl)-benzyl-chitosan using CuSO 4 ·5H 2 O and CuCl 2 ·2H 2 O salts was studied. The content of Cu 2+ in the complexes was determined by atomic absorption spectrometry and the results showed that chitosan exhibited higher chelating capacity for both salts. Morphological changes of derivatives and complexes were demonstrated by SEM–EDS. In addition, the presence of some crystals attributed to copper sulfate adsorbed on the polymer surface was also observed, which indicates that part of the metal content is in the salt adsorbed and might influence in the use of the materials for further application studies. This result was supported by Raman spectroscopy results in which vibrations of O=S=O groups were observed. X-ray diffraction patterns showed that the chemical modification of chitosan and formation of complexes resulted in the decrease of crystallinity. Electron paramagnetic resonance was used to investigate structural aspects of the materials complexed with Cu 2+ ions in the solid state.

Description: Novel bio-polyamides obtained from renewable resources, e.g. PA4.10, are considered nowadays as promising ‘green’ engineering materials consisting of building blocks derived from castor oil. In this work the composites of heterogeneously acetylated microfibrillated cellulose (MFC) and biopolyamide 4.10 have been prepared by melt blending. Thermoplastic processing of PA4.10/MFC composites was possible in a narrow temperature window due to significant improvement of thermal stability of acetylated MFC as compared to raw MFC. The increase of thermooxidative stability of filler was due to removal of non-cellulosic components from the raw material and introduction of acetic moieties that had additional slight stabilizing effect on MFC. Moreover, the modified MFC showed significant changes in morphology that favoured its dispersibility in viscous polymer melt. Combined treatment of MFC by chemical agents, which caused partial hydrolysis of amorphous regions, and physical disintegration by ultrasonic waves resulted in formation of fibrous material with low degree of entanglement and submicron or nanometric diameters. In the tested range of screw speeds it was found that at screw speed of 100 rpm the shearing forces were sufficient for dispersing MFC agglomerates and the melt pressure secured evacuation of gases introduced to plasticizing system of extruder with MFC-Ac aerogel. The dynamic mechanical properties of obtained (nano)composites were influenced by both mechanical strengthening of rigid cellulose micro and nanofibers as well as susceptibility of biopolymers towards oxidation and thermomechanical degradation during processing.

Description: The effect of a substitution site on orientation birefringence for cellulose triacetate (CTA) was investigated by the addition of xylan ester. Since CTA has three substitution sites (C-2, C-3, and C-6) while xylan ester has two substitution sites (C-2 and C-3), the change of birefringence by xylan acetate (XylAc) is attributed to the contribution of the C-6 acetyl group. Dynamic mechanical analysis and thermal measurements showed a single glass transition peak, indicating that XylAc is miscible with CTA at any compositions. The orientation birefringence (Δ n ) of CTA/XylAc films stretched beyond the glass transition temperature increased with increasing the XylAc content. The result for the stretched film suggested that the contribution of acetyl group in the C-2 and C-3 sites to Δ n is positive while that in the C-6 is negative. The negative sign for the C-6 site is in agreement with the result simulated by using the molecular dynamics method. In addition, Δ n of CTA films containing xylan propionate (or butyrate) indicated that the propionyl and butyryl groups in the C-2 and C-3 sites show positive birefringence similar to the acetyl group.

Description: Fiber mat materials based on cellulose natural fibers combines a useful set of properties, including renewability, stiffness, strength and dielectric insulation, etc. The dominant in-plane fiber orientation ensures the in-plane performance, at the expense of reduced out-of-plane behavior, which has not been studied as extensively as the in-plane behavior. Quantitative use of X-ray micro-computed tomography and strain analyses under in-situ loading open up possibilities to identify key mechanisms responsible for deformation. In the present investigation, focus is placed on the out-of-plane deformation under compressive loading of thick, high density paper, known as pressboard. The samples were compressed in the chamber of a microtomographic scanner. 3D images were captured before and after the loading the sample. From sequential 3D images, the strain field inside the material was calculated using digital volume correlation. Two different test pieces were tested, namely unpolished and surface polished ones. The first principal strain component of the strain tensor showed a significant correlation with the density variation in the material, in particular on the top and bottom surfaces of unpolished samples. The manufacturing-induced grooves generate inhomogeneities in the microstructure of the surface, thus creating high strain concentration zones which give a sensible contribution to the overall compliance of the unpolished material. More generally, the results reveal that, on the micrometer scale, high density fiber pressboard behaves as a porous material rather than a low density fiber network.

Description: The chemical degradation kinetics of cellulose is of scientific interest, as well as its practical importance in many industrial activities for optimal design. Much work has been done recently to understand the depolymerizaton of cellulose in homogeneous acidic medium on the assumption of autocatalytic hydrolysis with a positive feedback of acid production from the degraded biopolymer. Series solutions are obtained for concentrations of cellulose chains and degraded cellulose chains by Taylor series and variational iteration method. Depolymerization of cellulose strongly depends upon the initial conditions, and the concentration of cellulose chains changes exponentially with a linear and square/cubic time dependence. The analytical solution can be used for optimal design of the degradation process.

Description: Wood cellulose is a desirable inexpensive, abundant and biodegradable substrate material for flexible organic electronics. While paper-based conductors are easily achieved, their applicability for diode architectures is challenging. To diminish short circuits, smoothing fillers and coatings are used before diode deposition. In this report, an alternative approach for use of cellulose in organic photovoltaics is demonstrated, using natural, rough unmodified kraft pulp fiber networks as a carrier of a diode architecture. Silver nanowires are adsorbed by the hydroxyl groups of cellulose fiber, forming the semi-transparent anode. The follow-on coatings for the diode are simply deposited as a mantle on these fiber anodes. The potential of this approach is demonstrated by the first production of cellulose fiber-based P3HT:PCBM photovoltaic devices, showing clear diode behaviour in the dark and a significant photoresponse under illumination. Fill factors near 35 % and open-circuit voltages of 0.2 V were achieved without any optimization. Devices show even noticeable photocurrent at low unfavourable light conditions, indicating their advantageous capture of stray light within the paper fiber network. These results highlight that for “paper” diodes, its natural properties can be turned into advantages, instead of seeking routes to suppress them.

Description: In this study, an activated peroxide system was established for low-temperature bleaching of cotton by incorporating N -[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC), hydrogen peroxide (H 2 O 2 ) and sodium bicarbonate (NaHCO 3 ) into an aqueous solution. The bleaching performance was modelled by response surface methodology based on a central composite rotatable design of experiment, in which concentration of TBCC ([ TBCC ]), concentration of NaHCO 3 ([ NaHCO 3 ]), temperature ( T ) and time ( t ) were four independent variables, and the degree of whiteness (DoW) of bleached cotton was measured as the response variable. For each individual bleaching experiment, TBCC and H 2 O 2 were used in a molar ratio of 1:1.1 and NaHCO 3 in a molar amount greater than that of H 2 O 2 for the purpose of driving reactions to completion. A reduced quadratic model (RQM) was constructed using regression analysis with backward elimination, which was used to conduct a practical low-temperature bleaching process for cotton. In comparison to the typical conventional peroxide system, the TBCC-activated peroxide system based on the RQM predication provided cotton with an equivalent DoW and slightly inferior water absorbency, resulted in no apparent damage to cotton fibers, but worked under much milder conditions. This study provides useful insights into scaling up the TBCC-activated peroxide system for low-temperature bleaching of cotton.

Description: This study explores the biocompatible behavior of bacterial cellulose (BC) composites with the highly conductive poly(3,4-ethylenedioxythiophene)–poly(styrene sulfonate) (PEDOT:PSS). To synthesize this novel composite, we utilized an ex situ penetration method, whereby never-dried BC sheets were incubated with aqueous PEDOT:PSS solution. The resulting composite films were characterized using several analytical tools. Field-emission scanning electron microscopy illustrated the impregnation of PEDOT:PSS into the BC matrix, while the uniform dispersion of PEDOT:PSS in the composites was confirmed with energy-dispersive X-ray spectroscopy. The conductivity of the PEDOT:PSS incorporated BC was 7.3 × 10 −2  ± 0.021 S/cm with 29.37 ± 2.13 weight percentage (wt%) of PEDOT:PSS. The biocompatibility of the BC–PEDOT:PSS film was tested against animal fibroblast cells. The composites showed excellent cell adhesion and proliferation. The animal cells showed filopodia formation and interconnectivity during 3 days of incubation. The cytotoxicity of the BC–PEDOT:PSS film was also assayed, confirming the non-toxic nature of this composite. Taken together, our results demonstrate that this novel biocompatible BC–PEDOT:PSS composite could potentially be used for biomedical applications, particularly in the biosensors, drug delivery devices, neural implants, and tissue engineering fields.

Description: Esterification was used to improve the thermal stability of nanocellulose to extend its application as reinforcing filler to polymer matrices with high melting point. The effect of the structure of ester groups on thermal stability was studied in detail. Various types of nanocellulose esters (straight-chain, C2–C14; cyclic adamantoyl, ADM; aromatic benzoyl, BNZ; and branched pivaloyl, PIV) with degree of substitution values in the range of 0.40–0.47 were prepared from bacterial cellulose nanofibers and nanocrystals. The reaction conditions used to prepare the esters maintained the viscosity-average degree of polymerization (DPv) and crystallinity of the starting materials. Thermogravimetric analysis showed that the temperature at maximum weight loss rate (T max ) increased after esterification. The structure of the ester groups and the DPv, however, showed no varying effect on T max . The 5 % weight loss temperature (WLT) which was used to assess the thermal stability at the onset of thermal degradation varied with the type of ester. Lower 5 % WLT was observed in straight-chain esters than those of the bulky esters of ADM, BNZ and PIV; which also showed high resistance to weight loss when subjected to isothermal heating. To understand the event at the onset of thermal degradation, low temperature pyrolysis was conducted. The evolved gases were separated and identified by gas chromatography–mass spectrometry technique. Results showed that at the onset of thermal degradation, levoglucosan (LG) is produced from the untreated BC nanocrystals. After esterification, LG formation was inhibited. The removal of the ester groups or deprotection is the main event at the onset of thermal degradation of nanocellulose esters. From the structure of the pyrolysis products, the mechanism of thermal deprotection of nanocellulose esters is proposed for the first time.

Description: Sugar palm fiber (SPF) is one of the prospective fibers used to reinforce polymer composites. The aim of this study is to evaluate the physicochemical, thermal, and morphological properties of SPF after alkali and sea water treatments. The chemical constituents group and thermal stability of the SPF were determined using scanning electronic microscopy (SEM) along with energy dispersive X-ray spectroscopy and thermogravimetric analysis (TGA). Fourier transform infrared spectroscopy was carried out to detect the presence of functional groups in untreated and treated SPF. The SEM images after both treatments showed that the external surface of the fiber became clean as a result. However, the sea water treatment affected the fiber properties physically, while the alkali treatment affected it both physically and chemically by dissolving the hemicellulose in the fiber. The TGA results showed that untreated fiber is significantly more stable than treated fiber. In conclusion, the results show that the fiber surface treatment significantly affected the characterization of the fiber.

Description: Viscose fiber was oxidized with sodium periodate to prepare a reactive dialdehyde viscose fiber (DAVF) containing abundant aldehyde groups. A solid amine adsorbent (DAVF-PEI) with high amino density for CO 2 capture was then prepared by modifying DAVF with polyethylenimine (PEI). Response surface methodology (RSM) based on a three-level, three-factorial design was used to optimize the synthesis conditions of DAVF, in which multiple linear regression equations of aldehyde content and fiber mass loss degree were constructed. The well-designed DAVF was then employed as a support to graft with PEI via Schiff base reaction to prepare a solid amine fiber (DAVF-PEI) for CO 2 adsorption. The experimental results verified that DAVF-PEI possessed good thermo-stability and high CO 2 adsorption capacity (4.11 mmol/g). DAVF-PEI also showed promising regeneration performance, which could maintain almost the same adsorption capacity for CO 2 after ten adsorption and desorption recycles.

Description: Encapsulation of various materials on textiles is an interesting task because of the controlled release and higher stability. Here, a robust cotton fabric was prepared through novel simultaneous treatment and nano-encapsulation of Chamomile extract using Tragacanth gum (TG) as the wall material and an environmentally friendly binder with hydrogel properties. The nano-encapsulated and treated cotton (NE&TC) fabric was characterized by FESEM, FT-IR and UV-Vis spectrophotometry, which indicated the successful encapsulation of the plant extract within the TG and material and linkage on the cotton fabric. The peaks at 1736 and 1777 cm −1 related to the TG and Chamomile extract in the FT-IR spectrum and a strong peak around 270–400 nm in the UV-Vis spectrum of the NE&TC fabric confirmed the nano-encapsulation and treatment. The prepared NE&TC fabric indicated a relatively good washing and rubbing durability with reasonable release behavior. The DSC pattern of the NE&TC fabric showed a peak at 162 °C confirming the presence of  Chamomile extract in the nanocapsules. This article proposes a novel method for the application of TG as a natural polymer on cotton fabric for obtaining multifunction purposes including in-situ synthesis of encapsulated Chamomile extract, stabilization of nanocapsules and introduction of hydrogel properties.

Description: Recyclable and transparent nanocomposite films based on bacterial cellulose (BC) and hemiaminal dynamic covalent network polymer (HDCN) have been synthesized by in situ polymerization of 4,4′-diaminodiphenyl ether (ODA) with paraformaldehyde. Transparency and structural and mechanical properties of such nanocomposite films are investigated. It was found that BC/HDCN nanocomposite films exhibits a high optical transparency (86 % at 550 nm). Scanning electron microscopy reveals excellent compatibility of the reinforcement of BC nanofibers and HDCN matrix, which leads to the improvement of 20 and 200 % in tensile strength and storage modulus, respectively, as compared to neat HDCN films. BC hydrogels are readily recoverable from nanocomposite films by the sulphuric acid treatment and ODA monomer is deposited and also recycled.

Description: This article describes a facile route, which combines mild maceration of waste pulp sludge and a mechanical shearing process, to prepare microfibrillated cellulose (MFC) with a high storage modulus. In the maceration, the mixture of glacial acetic acid and hydrogen peroxide was used to extract cellulose from never-dried waste pulp sludge. Then, two different mechanical processes including disc refining (DR) and ultrasonication plus homogenization (UH) were applied to the cellulose after maceration and resulted in MFC with a highly tangled fibril network. All of the resultant cellulosic suspensions (2 % w/w) exhibited a gel-like and shear-thinning behavior with storage moduli ( G ′) ranging from 200 to 4000 Pa. Among them, the 30-min DR-treated MFC gels had the maximum G ′, which was much higher than for previously reported MFC gels at the same concentration. Additionally, after mechanical processing, specific surface areas and water retention values of MFC were accordingly increased with the enhancement of shear force, while the storage moduli ( G ′) were not consistently increased. Finally, a strong MFC gel was successfully prepared from never-dried waste pulp sludge via a one-step disc refining process and using cost-effective chemicals. The obtained hydrogels will have potential as low-density reinforcing fillers or as a template for further surface modification.

Description: A kind of viscose fiber fabric with permanent flame retardancy has been prepared by grafting polymerization of phosphorus and nitrogen-containing monomer, i.e. 2,2-dimethyl-1,3-propanediol acrylamide methoxyl phosphate (DPAMP) onto viscose fiber fabric (VF-g-DPAMP). The effects of the initiator concentration, DPAMP concentration, temperature, pH and time on grafting polymerization were studied, and the structure of VF-g-DPAMP was determined with Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy. The surface morphology of viscose fiber fabric and VF-g-DPAMP were studied by scanning electron microscope. The thermal property and fire retardant performance of VF-g-DPAMP were assessed by thermogravimetric analysis, limited oxygen index measurements and cone calorimeter test, respectively. The results show that DPAMP has been successfully grafted onto viscose fiber fabric, and VF-g-DPAMP has good char-forming ability and better fire retardancy. The pkHRR and THR of the grafted fabric decrease from 150 to 98 kW/m 2 and 5.70 to 1.73 MJ/m 2 , respectively.

Description: Paper-based devices enable low-cost mass production, wide availability and useful technical aspects such as light weight, mechanical bendability and natural integration in existing paper-based creations such as educational books, administrative documentation and artwork. While magneto-electronics and spintronics play an important role in delivering sensing, communication and data storage solutions, especially necessary in the framework of the internet of things, it is beneficial to achieve compatibility between this technology and paper materials. As a first example of paper-based magneto-electronics, we investigate the manufacturing of well performing anisotropic magneto-resistors on paper by means of low power sputter deposition of permalloy \((\hbox {Py:Ni}_{81}\hbox {Fe}_{19})\) , shadow mask patterning and magnetic clamping of the shadow mask. A range of commercially available papers were studied by varying most significant mechanical, chemical and geometrical attributes of the paper to this application. The dependence of magnetic properties (coercivity, saturation remanence and relative permeability) on the paper properties (surface roughness, stiffness and paper making process) was studied based on magnetic characterization, surface profilometry and elemental analysis. Subsequently, conclusions on the optimal magnetic \(\hbox {Py:Ni}_{81}\hbox {Fe}_{19}\) -on-paper system were drawn.

Description: In this work, wheat bran was used as cellulosic filler in biocomposites based on natural rubber. The impact of wheat bran content [ranging from 10 to 50 parts per hundred rubber (phr)] on processing, structure, dynamic mechanical properties, thermal properties, physico-mechanical properties and morphology of resulting biocomposites was investigated. For better characterization of interfacial interactions between natural rubber and wheat bran, achieved results were compared with properties of biocomposites filled with commercially available cellulosic fillers—wood flour and microcellulose. It was observed that wheat bran, unlike commercial cellulosic fillers, contains high amount of proteins, which act like plasticizers having profitable impact on processing, physical, thermo-mechanical and morphological properties of biocomposites. This is due to better dispersion and distribution of wheat bran particles in natural rubber, which results in reduction of stiffness and porosity of the biocomposites. Regardless of cellulosic filler type, Wolff activity coefficient was positive for all studied biocomposites implying reinforcing effect of the applied fillers, while tensile strength and elongation at break decreased with increasing filler content. This phenomenon is related to restricted strain-induced crystallization of NR matrix due to limited mobility of polymer chains in the biocomposites. Furthermore, this explains negligible impact of particle size distribution, chemical composition and crystallinity degree of applied cellulosic filler on static mechanical properties of highly-filled NR biocomposites. The conducted investigations show that wheat bran presents interesting alternative for commercially available cellulosic fillers and could be successfully applied as a low-cost filler in polymer composites.

Description: Guar gum (GG) fracturing fluids were studied by incorporating cellulose nanofibrils (CNFs) in anhydrous borax crosslinked guar gum gels. To fully understand the impact of CNF on the proppant suspension capability of developed fracturing fluids, their shear rate-dependent viscosity and viscoelasticity were investigated. The shear rate dependencies of fluids was fitted to the Carreau model. The zero shear rate viscosity and elasticity of fracturing fluids increased significantly by incorporating CNF in guar gum gels. On the other hand, the viscosity at high shear rates (〉100 s −1 ) decreased as desired. The proppant settling velocities through fracturing fluids were evaluated by modeling the terminal falling velocity of proppants moving through a Carreau model fluid. The experimental results of the rheological behavior and the modeling results of the proppant settling rate indicated that the fracturing fluids containing CNF had better suspension capabilities. In addition, the lower viscosities of CNF formulated GG gels at higher shear rates will make them more pumpable.

Description: Novel cellulose–chitosan nanocomposite particles with spherical shape were successfully prepared via mixing of aqueous biopolymer solutions in three different ways. Macroparticles with diameters in the millimeter range were produced by dripping cellulose dissolved in cold LiOH/urea into acidic chitosan solutions, inducing instant co-regeneration of the biopolymers. Two types of microspheres, chemically crosslinked and non-crosslinked, were prepared by first mixing cellulose and chitosan solutions obtained from freeze thawing in LiOH/KOH/urea. Thereafter epichlorohydrin was applied as crosslinking agent for one of the samples, followed by water-in-oil (W/O) emulsification, heat induced sol–gel transition, solvent exchange, washing and freeze-drying. Characterization by X-ray photoelectron spectroscopy, total elemental analysis, and Fourier transform infrared spectroscopy confirmed the prepared particles as being true cellulose–chitosan nanocomposites with different distribution of chitosan from the surface to the core of the particles depending on the preparation method. Field emission scanning electron microscopy and laser diffraction was performed to study the morphology and size distribution of the prepared particles. The morphology was found to vary due to different preparation routes, revealing a core shell structure for macroparticles prepared by dripping, and homogenous nanoporous structure for the microspheres. The non-crosslinked microparticles exhibited a somewhat denser structure than the crosslinked ones, which indicated that crosslinking restricts packing of the chains before and under regeneration. From the obtained volume-weighted size distributions it was found that the crosslinked microspheres had the highest median diameter. The results demonstrate that not only the mixing ratio and distribution of the two biopolymers, but also the morphology and nanocomposite particle diameters are tunable by choosing between the different routes of preparation.

Description: Gram’s Iodine Assay is currently used to detect endoglucanase, a cellulase enzyme which cleaves β-1,4-glycosidic bonds in carboxymethylcellulose (CMC). When a zone of degradation was observed around non-cellulolytic Escherichia coli JM109 with the use of Gram’s Iodine, the assay was further examined. Additional cellulolytic bacteria were chosen to display these inconsistencies. Bacillus thuringiensis subsp. Kurstaki ( Btk ) and Cellulomonas persica , known to possess endoglucanase, were incubated at 30 °C for 48 h on several different media; 1.5 % agar only, Davis minimal media, CMC agar, non-CMC agar, and Phytagel CMC. After the incubation period all plates were flooded with Gram’s Iodine for 3–5 min. A clear ring of degradation was identified around colonies in plates containing no cellulose and plates containing agar only. When agar was removed as the solidifying agent and substituted with Phytagel, zones of clearing around cellulolytic organisms were altered. These findings indicate that agar alone can cause additional artifacts and should be replaced by other solidifying agents as well as supplementation of the Congo Red Assay. Taking these precautions can overcome inconsistency problems for future cellulolytic screenings.

Description: Microcrystalline cellulose (MCC) was modified with pyridone derivatives such as pyridone diester (PDE) and pyridone diacid (PDA) by using succinic acid anhydride as a linker. The modified MCCs were characterized by the fourier transform infrared spectroscopy, scanning electron microscopy, thermal gravimetric analysis, elemental analysis and solid state 13 C NMR. The adsorption capacities of the modified MCCs to cationic dyes were examined by using methylene blue (MB) as a model dye. It was found that the kinetic adsorption data followed the pseudo-second-order kinetic model, and the adsorption equilibriums were reached less than 10 min. The isothermal adsorption data were fitted with the Langmuir isotherm model very well, from which the maximum adsorption capacities of the MCCs modified with PDE and PDA were determined to be 101.01 and 142.86 mg/g, respectively. Further investigation showed that the modified MCCs were pH-dependent for adsorption of MB in aqueous solutions. The modified MCCs could be used for removal of MB from an aqueous solution at pH 8, and reused by regeneration in an acidic solution. It was tested that the modified MCCs had a high reusability for removal of MB from aqueous solutions, and still maintained high adsorption capacities even after multiple cycles of desorption–adsorption processes. Hence, the MCCs modified with PDE and PDA could be an effective and efficient approach to removal of cationic dyes from aqueous solutions.

Description: Chemical cationization of cotton has been a subject of increased interest due to the ability of cationized cotton to attract negatively charged dyes, thus eliminating the use of electrolytes during dyeing and increasing color yield. However, electrostatic attractions between cationized cotton and anionic dyes also result in significantly increased dye strike rates, which may cause levelness problems, especially when light to medium shades are required. In this study, cotton fabric cationized using 3-chloro-2-hydroxypropyl trimethylammonium chloride was used to investigate the method for obtaining appropriate dye strike rate to produce a level reactive dyeing on cationized cotton. To effectively control the dyeing kinetics of reactive dyes on cationized cotton, real-time exhaustion of six commercially significant reactive dyes were monitored. The influence of temperature, dye structure, and addition of soda ash on dyeing kinetics and levelness of cationized cotton were evaluated.

Description: Cotton woven fabrics were first dyed with a graphene oxide (GO) aqueous dispersion using a simple industrialized exhaustion dyeing process. The resulting fabrics were then chemically reduced to prepare the electrically conductive cotton fabrics. They were characterized by the FE-SEM, XPS and Raman spectrum and evaluated with respect to whiteness, electrical surface resistance and electrochemical impedance spectroscopy. Some factors affecting the process such as the GO concentration, dyeing and reducing conditions, and nature and concentration of the reducing agent were also investigated. The results indicated that GO could be fixed on cotton fabric by a simple exhaustion dyeing process and converted into the reduced GO (RGO) with a reducing agent. Increasing the GO concentration or dyeing temperature and time decreased the whiteness and electrical surface resistance of the RGO-dyed fabric. However, higher pH showed a reverse effect. Na 2 S 2 O 4 was found to be a stronger reducing agent for the conversation of GO into RGO on cotton fabric than ascorbic acid and thiourea. The reduction of GO-dyed fabric was easily completed by an increasing Na 2 S 2 O 4 concentration at higher temperature. Moreover, an increasing number of dyeing cycles decreased the surface resistance and impedance modulus and increased the abrasion resistance of the RGO-dyed cotton fabric.

Description: Surface functionalization of textiles is crucial in developing protective clothing that protects wearers from potential hazards of liquid, chemical and biological contamination. This study aims to explore chemical and water protective surface on cotton fabric by pad-knife-pad coating of waterborne polyurethane (WPU), polydimethylsiloxane (PDMS) and trimethylated silica (TMS). The chemical structure of the coated cotton fabrics was characterized by attenuated total reflectance Fourier transform infrared spectroscopy. Surface wettability and liquid protective properties of the coated cotton fabrics were analyzed by water contact angle, water repellency, hydrostatic pressure, and oil and aqueous liquid repellency. It was revealed that WPU and PDMS-TMS formed copolymerization reactions, resulting in ultrahydrophobic, oil repellent and mechanically strong membrane on the surface of cotton fabric. It has been found that the coating of WPU-PDMS-TMS makes cotton fabric highly resistant to water, oil and aqueous liquids. This surface functionalization technology can be further applied in developing protective clothing with chemical and water resistant and self-cleaning properties.

Description: Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite (NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC–NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Ω/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Ω/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2 (5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film’s surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC–NG films that are mechanically stable, bendable, and flexible.

Description: Highly water-soluble cyclosophoraose (Cys) has been recently used as a suitable complexation agent to enhance the solubility of drugs that are hardly water-soluble by molecular encapsulation via host–guest complexation. In this study, a novel Cys/cellulose hydrogel was prepared by cross-linking Cys and cellulose for efficient galangin delivery to improve antibacterial activity. Galangin was known to directly inhibit the activity of β-lactamase and to exhibit intrinsic antibacterial activity. The inhibition of β-lactamase by galangin was also known to enhance the eradication of a strain of methicillin-resistant Staphylococcus aureus . However, efficient delivery of galangin in an aqueous solution for improved antibacterial activity could not be achieved because of its extremely poor water solubility and bioavailbility. The structure and morphology of the resulting hydrogels were verified using with various instrumental techniques using rheometer, FT-IR spectroscopy, solid-state NMR spectroscopy, XRD and FE-SEM. The loading amount of galangin increased as the Cys content in the hydrogels increased, with a release time of 48 h. The galangin loading amount and its cumulative amount released from the Cys/cellulose hydrogel were 1.62- and 1.64-fold greater than those of galangin released from cellulose hydrogel, respectively. Additionally, the galangin-loaded Cys/cellulose hydrogel had antibacterial activity against S. aureus , with growth inhibition maintained up to 72 h. Furthermore, the Cys/cellulose hydrogel did not show any cytotoxicity toward human dermal fibroblasts. Throughout the study, the Cys/cellulose hydrogel demonstrated potential advantages as an efficient antibacterial dressing material for galangin delivery through targeting of drugs to the wound site in a sustained manner over a long period without frequent dressing changes.

Description: The extensional flow behaviors of cellulose/NaOH/urea/H 2 O solution were investigated by using capillary breakup extensional rheometry (CaBER). The effects of temperature, storage time and cellulose concentrations on both the storage modulus G ′ and the loss modulus G ″ were also analyzed. For 2 wt% cellulose solution, the G ′, G ″ and filament lifetime remained unchanged after long storage time. While, for 4 wt% cellulose solution, physical gels could form at either higher temperature or for longer storage time, and the filament lifetime, the relaxation time ( λ e ) and the initial extensional viscosity ( η e 0 ) first increased and then decreased with increase of the storage time. The transition points of the filament lifetime shifted to lower storage time with the increase of the temperature. The η e 0 is proportional to λ e . The results presented suggest that the extensional properties of the cellulose/NaOH/urea/H 2 O solution first increase and then decrease during the gelation process, and the spinning time, which decreases linearly with the increase in the storage temperature, must be controlled below the time that η e 0 starts to decrease.

Description: A novel preparation route of zinc oxide (ZnO)–cellulose composite was developed via synthesis of ZnO in partially dissolved cellulose. Filter paper was partially dissolved in zinc chloride (ZnCl 2 ) solution. Then, the ZnO–cellulose composite was achieved when the partially dissolved cellulose was reacted with sodium hydroxide (NaOH) solution. Several factors affecting the ZnO content and mechanical properties of the composite were investigated. The ZnO–cellulose composite was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and energy dispersive X-ray spectroscopy. Compared to the untreated paper, the ZnO–cellulose composite had high compactness. Meanwhile, its tensile strength and folding strength were improved two times and fifteen times, respectively. Cellulose fibers treated with this method had the skeleton of un-dissolved cellulose fibers, the matrix of gelled cellulose, and flower-like ZnO nanoplate on cellulose surface. In addition, the antibacterial property was identified from the ZnO–cellulose composite.

Description: Wood pulp cellulose nanofibrils (CNF) thin film is a novel recyclable and biodegradable material. We investigated the microwave dielectric properties of the epoxy coated-CNF thin film for potential broad applications in flexible high speed electronics. The characterizations of dielectric properties were carried out in a frequency range of 1–10 GHz. The dielectric constant and loss tangent were extracted by using measurements of microstrip transmission lines that were built on the epoxy coated-CNF film and combined with Agilent Advanced Design System simulations. The RF property for the epoxy coated-CNF was compared to that of commercial polyethylene terephthalate film (PET). With the comparable microwave properties of non-biodegradable PET film, our study suggests that the epoxy coated-CNF film is a suitable biodegradable and environment-friendly substrate for flexible microwave and other applications.

Description: In recent years, nanofibrous mats derived from biopolymers have attracted more interest and attention for biomedical applications, such as wound dressing, tissue engineering, and drug delivery. In this study, carboxymethyl cellulose/Ag nanoparticles (CMC/Ag NPs) nanofibrous membranes were prepared via a simple and green method in which electrospun CMC/poly(ethylene oxide) membranes were immersed in AgNO 3 solution, followed by reduction of Ag + –Ag NPs upon ultraviolet (UV) irradiation. Notably, as evidenced by Fourier-transform infrared (FTIR), X-ray diffraction (XRD), and thermogravimetric (TG) analyses, poly(ethylene oxide) was eliminated during the immersion process and CMC nanofibrous mats containing Ag NPs were obtained. The effects of UV wavelength, AgNO 3 solution concentration, and irradiation time on the morphology of the CMC/Ag NPs membranes were investigated, revealing optimal parameters (254 nm wavelength, 0.1 mol/L AgNO 3 solution, and 10 min irradiation time) under which Ag NPs with average diameter of 20 nm were uniformly distributed on the surface of fibers. Antibacterial tests indicated that the antibacterial efficiency against Escherichia coli and Staphylococcus aureus of the obtained CMC/Ag NPs membranes reached up to 100 %, suggesting great potential for use as antimicrobial dressings.

Description: Sago seed shells are agricultural wastes that are discarded after taking the pith. The composition of sago seed shells has been determined by using standard methods. Parameters such as extractives (ASTM D1107-96), Klason lignin (ASTM D1106-96), holocellulose (Wise et al. in Paper Trade J 122(2):35–42, 1946 ), α-cellulose (ASTM D 1103-60), hemicellulose (by difference) and ash content (T 211 om 02) were determined. The components were characterised using FTIR, TGA, XRD, SEM, TEM and AFM. The detailed spectral, thermal, XRD and SEM analyses show the presence Klason lignin, holocellulose and α-cellulose. α-Cellulose has been converted into microcrystalline cellulose (MCC) by acid hydrolysis. MCC was also characterised by using FTIR, TGA, XRD, SEM, TEM and AFM. Frequencies of the FTIR spectrum are similar to those of α-cellulose, and the TGA data reveal increased decomposition temperatures for MCC and well as a well defined TGA curve, indicating the increased structural order or crystallinity. This is further supported by XRD. SEM, TEM and AFM results, which reveal the microstructural behavior of isolated MCC.

Description: The drive towards sustainability, even in materials technologies, has fuelled an increasing interest in bio-based composites. Cellulosic fibres, such as flax and jute, are being considered as alternatives to technical synthetic fibres, such as glass, as reinforcements in fibre reinforced polymer composites for a wide range of applications. A critical bottleneck in the advancement of plant fibre composites (PFRPs) is our current inability to predict PFRP properties from data on fibre properties. This is highly desirable in the cost- and time-effective development and design of optimised PFRP materials with reliable behaviour. This study, alongside limited other studies in literature, have found that the experimentally determined (through single fibre tests) fibre properties are significantly different from the predicted (‘back-calculated’ using the popular rule-of-mixtures) fibre properties for plant fibres. In this note, we explore potential sources of the observed discrepancy and identify the more likely origins relating to both measurement and errors in predictions based on the rule-of-mixtures. The explored content in this discussion facilitates the design of a future investigation to (1) identify the sensitivity of the discrepancy between measured and predicted fibre properties to the various potential origins, (2) form a unified hypothesis on the observed phenomenon, and (3) determine whether the rule-of-mixtures model (in specific cases) can be improved and may be able to predict properties precisely.

Description: Enzymatic hydrolysis of cellulose provides a renewable source of monosaccharides for production of variety of biochemicals and biopolymers. Unfortunately, the enzymatic hydrolysis of cellulose is often incomplete, and the reasons are not fully understood. We have monitored enzymatic hydrolysis in terms of molecular density, ordering and autofluorescence of cellulose structures in real time using simultaneous CARS, SHG and MPEF microscopy with the aim of contributing to the understanding and optimization of the enzymatic hydrolysis of cellulose. Three cellulose-rich substrates with different supramolecular structures, pulp fibre, acid-treated pulp fibre and Avicel, were studied at microscopic level. The microscopy studies revealed that before enzymatic hydrolysis Avicel had the greatest carbon-hydrogen density, while pulp fibre and acid-treated fibre had similar density. Monitoring of the substrates during enzymatic hydrolysis revealed the double exponential SHG decay for pulp fibre and acid-treated fibre indicating two phases of the process. Acid-treated fibre was hydrolysed most rapidly and the hydrolysis of pulp fibre was spatially non-uniform leading to fractioning of the particles, while the hydrolysis of Avicel was more than an order of magnitude slower than that of both fibres.

Description: Four sources of cellulose with different molecular weights were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate at 100 °C over a 10 h period. The solution densities were determined and these results were subsequently utilised to access the influence of dissolved cellulose on surface tension properties of cellulose/ionic liquid solutions. Surface tension measurements revealed increasing molecular weight and concentration reduced surface tension while temperature increases showed the opposite effect. These results are consistent with that of repulsive polymer-wall interactions near the interface in good solvent conditions. The semi-flexible nature of this carbohydrate in solution can help explain deviations of these results when compared to ideal flexible chains.

Description: Preparation of nanocrystalline cellulose (NCC) by 62 and 65 % wt. sulfuric acid hydrolysis of cellulase-pretreated fibers was optimized to obtain the highest yield by applying two statistical plans. At optimal conditions (10 U/g odp cellulase, 25 min hydrolysis, 47 °C, 62 wt.% H 2 SO 4 ), high yields (≥80 %) were obtained, including an increase of ~9 points due to the enzyme. Optimal conditions produced nanosized particles of around ~200 nm with reduced surface charge and sulfur content. The optimization allowed reduction of hydrolysis time by 44 % and increase of yield by more than 10 points compared with results in previous work. The effects of cellulase pretreatment were noticeable even under aggressive hydrolysis conditions, emphasizing its possibilities. Zeta potential and polydispersity index indicated that all studied conditions led to good-quality final products, with values around −50 mV and 0.2, respectively. Transmission electron microscopy (TEM) analysis confirmed the presence of NCC. Fourier-transform infrared (FTIR) spectroscopic analysis provided evidence that cellulase treatment increased the crystallinity of both cellulose fibers and NCC, as well as fiber accessibility, supporting the other analyses of NCC.

Description: Porous sheets with high mechanical strength were prepared with natural pulp fibers (hardwood and softwood bleached kraft pulp) and polyethylene terephthalate (PET) by adding cellulose nanofibrils (CNF) through a wet-laid forming method. The structure and mechanical properties of the porous sheets were investigated in this study depending on the type of mixed fibers, the CNF ratio, and drying methods (cylinder-drying and freeze-drying). The apparent density and porosity of porous sheets changed according to the morphology of the mixed fibers. PET fibers resulted in a sheet with a bulkier structure, whereas natural pulp fibers produced relatively dense sheets. Sheets with high porosity could be prepared by freeze-drying due to the inhibition of hydrogen bonds and low shrinkage during drying. Pore characteristics were evaluated in terms of air permeability and average pore diameter. The air permeability of porous sheets decreased as the amount of CNF increased. Mercury porosimetry showed that the average pore diameter in sheets ranged from 0.6 to 36.7 µm depending on the type and mixing ratio of fibers and drying conditions. Sheet tensile properties were improved by the addition of CNF and changed depending on mixing combinations and drying methods. The applicability of freeze-dried porous sheets as filter media was examined by evaluating the filtration efficiency and pressure drop. Porous sheets with a HwBKP/CNF combination showed a filtration efficiency of 99.944 %, which approached the efficiency of a high efficiency particulate air filter. However, further study is required to reduce the pressure drop during filtration for better use as an air filter.

Description: A relatively new approach for wood protection against fungal decay is based on hydrophobization of wood and on lowering its moisture content. Water repellence of wood can be increased by polymerization of hydrophobic monomers in wood cell walls. It was found that Norway spruce wood after treatment with octadecyltrichlorosilane exhibited reduced water uptake by the wood cell walls, lowered water vapour sorption, and significantly increased dimensional stability of wood in terms of anti-swelling efficiency. Hydrophobicity and lower equilibrium moisture content were shown to cause increased resistance of the treated samples against brown-rot decay and molds.

Description: Recent emphasis on the pilot scale production of cellulosic nanomaterials has increased interest in the effective use of these materials as reinforcements for polymer composites. An important, enabling step to realizing the potential of cellulosic nanomaterials in their applications is the materials processing of CNC/polymer composites through multiple routes, i.e. melt, solution, and aqueous processing methods. Therefore, the objective of this research is to characterize the viscoelastic behavior of aqueous nanocomposite suspensions containing cellulose nanocrystals (CNCs) and a water-soluble polymer, poly(vinyl alcohol) (PVA). Specifically, small amplitude oscillatory shear measurements were performed on neat PVA solutions and CNC-loaded PVA suspensions. The experimental results indicated that the methods used in this study were able to produce high-quality nanocomposite suspensions at high CNC loadings, up to 67 wt% with respect to PVA. Additionally, the structure achieved in the nanocomposite suspensions was understood through component attributes and interactions. At CNC loadings near and less than the percolation threshold, a polymer mediated CNC network was present. At loadings well above the percolation threshold, a CNC network was present, indicated by limited molecular weight dependence of the storage modulus. Overall, these results provide increased fundamental understanding of CNC/PVA suspensions that can be leveraged to develop advanced aqueous processing methods for these materials.

Description: A method based on direct UV-detection was developed for the qualitative and quantitative determination of oligosaccharides simultaneously separated by capillary electrophoresis (CE). Reference compounds consisting of five xylo- three manno- and five cello-oligosaccharides were concurrently measured in a highly alkaline solution without derivatization. Sodium and potassium cations were used in the electrolyte solution to adjust the electrokinetic properties of the oligomers by controlling the mobility of charged species and to improve the resolution in baseline separation. The quantification range extended from 25 to 125 mg/L with linear correlation \(\hbox {R}^{2}=0.986{-}0.997\) for all analytes other than xylobiose and cellobiose, for which the range was 50–200 mg/L ( \(\hbox {R}^{2}=0.995\) ). The CE method developed was further applied to determine oligosaccharides from hot-water extracts of a bleached birch and pine kraft pulp, in which the oligosaccharides typically exist as complex mixtures.

Description: The axial modulus of the cellulose Iβ crystal is as high as 120–160 GPa. The importance of hydrogen bonds is often emphasized in this context, although intrinsic stiffness of the hydrogen bonds is relatively low. Here, hydrogen bond–covalent bond synergies are investigated quantitatively using molecular mechanics and molecular dynamics simulations for the so-called leverage effect, a model introduced recently in which strains for intra-molecular hydrogen bonds are higher than for the cellulose chain as a whole, thereby amplifying their contribution to the total stiffness. The present work also includes simulation of the hydrogen bonding band shifts in vibrational spectra during cellulose deformation, which are compared with FT-IR data. The leverage effect hypothesis was supported by the results, although the total contribution to cellulose stiffness is only 12 %. Hydrogen bonding is still critically important and would lower the modulus much more than 12 %, if “artificially” removed in the model. The reason is that intra-molecular hydrogen bonding preserves the crystal structure and directs axial deformation mechanisms towards higher energy deformation and high stiffness.

Description: For simply and accurately determining molecular weight of cellulose, an ionic liquid mixed with a co-solvent, 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide (BmimAc/DMSO) (1:1, w/w) was used and dissolved cellulose well at ambient temperature. During the dissolution process no degradation of cellulose was observed, and all the resultant cellulose/BmimAc/DMSO solutions were transparent and stable. These advantages make it as an ideal solvent system to build a new characteristic method of cellulose’s molecular weight by the measurement of the intrinsic viscosity [η], which is significantly better than the currently used solvent systems. [η] of solutions of nine cellulose samples was measured by using rheometer with cylinder fixture and Ubbelohde viscometer, respectively. The [η] values obtained by these two methods were well consistent. The degree of polymerization (DP) of these cellulose samples was determined by Copper (II) ethylenediamine method. Then the molecular weight and its distribution of representative samples were cross-checked by gel permeation chromatography for soluble derivatives of cellulose. As a result, a relationship DP = 134 [η] 1.2 was built, suitable for DPs in the range of 220–1400. The uncertainty of this relationship was estimated to be 5 %. This work provided a simple, accurate and reliable method for determining [η] and the molecular weight of cellulose.

Description: The membrane and solute diffusion properties of Cladophora cellulose and polypyrrole (PPy) functionalized Cladophora cellulose were analyzed to investigate the feasibility of using electroactive membranes in hemodialysis. The membranes were characterized with scanning electron microscopy, ζ-potentiometry, He-pycnometry, N 2 gas adsorption, and Hg porosimetry. The diffusion properties across the studied membranes for three model uremic toxins, i.e. creatinine, vitamin B12 and bovine serum albumin, were also analyzed. The characterization work revealed that the studied membranes present an open structure of weakly negatively charged nanofibers with an average pore size of 21 and 53 nm for pristine cellulose and PPy-Cladophora cellulose, respectively. The results showed that the diffusion of uremic toxins across the PPy-Cladophora cellulose membrane was faster than through pure cellulose membrane, which was related to the higher porosity and larger average pore size of the former. Since it was found that the average pore size of the membranes was larger than the hydrodynamic radius of the studied model solutes, it was concluded that these types of membranes are favorable to expand the Mw spectrum of uremic toxins to also include conditions associated with accumulation of large pathologic proteins during hemodialysis. The large average pore size of the composite membrane could also be exploited to ensure high-fluxes of solutes through the membrane while simultaneously extracting ions by an externally applied electric current.

Description: Inspired by the surface structure of lotus leaves, different types of superhydrophobic cellulosic materials with contact angle (CA) of higher than 150° are currently provided. However, fabrication of these surfaces in a facile one-step coating process is one of the challenging issues. This paper describes a facile method to sonochemically synthesize superhydrophobic organic–inorganic hybrid coatings on cotton fabric by an alkaline-catalyzed co-hydrolysis and co-condensation of tetraethylorthosilicate and alkyltrialkoxysilanes. The influence of alkyl chain length (methyl, octyl, hexadecyl) of silane and reaction time was investigated. Surface structure of the fabrics was investigated by SEM, EDS, FTIR spectroscopies, and reflectance spectrophotometry. Wettability properties were studied by measuring water CA, shedding angle (SHA) and resistance to wetting by a series of ethanol–water mixtures of different surface tensions. The results showed that the treated fabrics were coated with a homogeneous thin nano-scaled coating of hybrid silica nano-particles. The fabrics demonstrated CA of higher than 150°, SHA in the range of 6–24° and different stickiness to water droplets. The fabrics treated by silanes with longer alkyl chain length and at higher reaction time revealed better water repellency. The coatings were nearly transparent, could not affect the color of the fabrics and had high stability against repeated washing. In addition, mechanical properties of the fabrics were not substantially affected.

Description: Composites of cellulose acetate and polysiloxane were prepared using 3-isocyanatepropyltriethoxysilane, as a coupling agent. The structure, the thermal and dynamic-mechanical behaviors, and the morphology of the obtained composites were investigated. The composites showed phase separation which was confirmed by the presence of siloxane micro- and nano-domains dispersed in the cellulose acetate matrix, with good interfacial adhesion between the phases. The results demonstrated that the incorporation of a polysiloxane phase on a cellulose acetate matrix caused a decrease in the glass transition temperature, storage modulus and hardness. The proposed methodology was seen to be convenient for the preparation of cellulose acetate/polysiloxane composites with useful properties.

Description: The effect of surface hydrophobicity and side-chain variation on xyloglucan adsorption onto cellulose microfibrils (CMF) is investigated via molecular dynamics simulations. A molecular model of CMF with (100), (010), (1–10), (110) and (200) crystal faces was built. We considered xylogluco-oligosaccharides (XGO) with three repeating units, namely (XXXG) 3, (XXLG) 3 , and (XXFG) 3 (where each (1,4)-β- d -glucosyl residue in the backbone is given a one-letter code according to its substituents: G = β- d -Glc; X = α- d -Xyl-(1,6)-β- d -Glc; L = β- d -Gal-(1,2)-α- d -Xyl-(1,6)-β- d -Glc; F = α- l -Fuc-(1,2)-β- d -Gal-(1,2)-α- d -Xyl-(1,6)-β- d -Glc). Our work shows that (XXXG) 3 binds more favorably to the CMF (100) and (200) hydrophobic surfaces than to the (110), (010) and (1–10) hydrophilic surfaces. The origin of this behavior is attributed to the topography of hydrophobic CMF surface, which stabilizes (XXXG) 3 in flat conformation. In contrast, on the rough hydrophilic CMF surface (XXXG) 3 adopts a less favorable random-coil conformation to facilitate more hydrogen bonds with the surface. Extending the xyloglucan side chains from (XXXG) 3 to (XXLG) 3 hinders their stacking on the CMF hydrophobic surface. For (XXFG) 3 , the interaction with the hydrophobic surface is as strong as (XXXG) 3 . All three XGOs have similar binding to the hydrophilic surface. Steered molecular dynamics simulation was performed on an adhesive model where (XXXG) 3 was sandwiched between two CMF hydrophobic surfaces. Our analysis suggests that this sandwich structure might help provide mechanical strength for plant cell walls. Our study relates to a recently revised model of primary cell walls in which extensibility is largely determined by xyloglucan located in limited regions of tight contact between CMFs.

Description: The aims of the present study were to prepare hydroxypropylmethyl cellulose (HPMC)-based porous matrix tablets for gastroretentive drug delivery and to characterize their physicochemical properties. Gabapentin (GBP) was used as a model drug. Paste containing GBP, HPMC and water was molded and freeze-dried to prepare freeze-dried gastroretentive matrix tablet (FD-GRT). In vitro drug release and erosion studies were also performed. Although FD-GRT exhibited porous structure, they had good tablet strength and friability. Density of FD-GRT ranged from 0.402 to 0.509 g/cm 3 and thus they could float on the medium surface without any lag time. FD-GRT was remained floated until the entire matrix erosion or end of drug release during in vitro release test. Release behavior of GBP could be modulated by the amount and the viscosity grade of HPMC. However, large amount and high viscosity of HPMC caused trouble in molding prior to freeze-drying. Addition of ethylcellulose could retard the release rate of GBP, with relatively low increase in viscosity of paste. Since pores generated by freeze drying imparted buoyancy for gastric retention to FD-GRT, additional materials for buoyancy was not necessary and FD-GRT had no lag time for buoyancy due to low density. Therefore it could be a promising tool for gastroretentive drug delivery.

Description: Introductory material first describes electron density approaches and demonstrates visualization of electron lone pairs and bonding as concentrations of electron density. Then it focuses on the application of Bader’s Quantum Theory of Atoms-in-Molecules (AIM) to cellulose models. The purpose of the work is to identify the various interactions that stabilize cellulose structure. AIM analysis aids study of non-covalent interactions, especially those for which geometric criteria are not well established. The models were in the form of pairs of cellotriose molecules, methylated at the O1 and O4 ends. Based on the unit cell of cellulose Iβ, there were corner–corner, and center–center pairs that correspond to (200) sheets, and corner–center pairings that corresponded to (1–10) and (110) stacks. AIM analysis (or charge-density topology analysis) was applied before and after minimization in vacuum and in continuum solvation. Besides the conventional O–H···O hydrogen bonds, all of which were known from geometric criteria, C–H···O hydrogen bonds (some previously reported), and some O···O and H···H interactions were found. Non-covalent bonds in the (200) sheets were maintained in all calculations with the exception of a weak, bifurcated O6–H···O2′′ bond that was not found in the corner–corner pair model and did not survive minimization. Nor did the O6···O4 interactions on the reducing ends of the triosides. Pairs of molecules along the (110) plane had an equal number (12) of non-covalent bonds compared to the pairs along the (1–10) plane, but the AIM parameters indicated the bonds between the pairs in the (110) plane were weaker. Intra-molecular O–H···O hydrogen bonds survived in these minimized pairs, but the relative chain alignments usually did not.

Description: A major by-product of biodiesel production is waste glycerol, which has numerous potential applications. In this study, we isolated a novel bacterium capable of producing cellulose from waste glycerol, and identified it as a novel strain (named NEDO-01) of Gluconacetobacter intermedius . Scanning electron microscopy revealed that the morphology of the pellicle produced by NEDO-01 was similar to that of cellulose produced by Gluconacetobacter hansenii ATCC23769. Furthermore, X-ray diffraction and solid-state nuclear magnetic resonance spectroscopic analyses suggested that cellulose produced by NEDO-01 had molecular and crystalline structures similar to those of cellulose produced by ATCC23769. After the optimization of cultivation conditions, NEDO-01 mediated the one-step production of nanofibrillated bacterial cellulose (NFBC) from waste glycerol in a medium supplemented with carboxymethyl cellulose. Transmission electron microscopic analysis revealed that the NFBC was composed of relatively uniform fibers with diameters of approximately 20 nm. NFBC was produced as uniform water suspensions, the yield of which was 3.4 g/L from cultivation in 7.5 L medium in a 10-L jar fermenter. The bioconversion of waste glycerol to NFBC, which has superior fluidity, moldability, and miscibility, has a wide variety of applications, including potential uses in the medical and materials engineering fields.

Description: Quaternary ammonium salts and N -halamines are widely used as biocides in antimicrobial coatings, and have been extensively studied over the past two decades. In this work, 5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin (SPH), and 3-(trimethoxysilylpropyl) octadecyl dimethyl ammonium chloride (SPODA) were synthesized and coated onto cotton fibers using a pad-dry process (PD) and the traditional pad-dry-cure process (PDC). The coated cotton swatches were characterized by FT-IR and SEM. The quaternary ammonium salt showed a relatively lower inactivating bacteria efficacy than did the N -halamine compounds. The chlorinated swatches coated with both SPH and SPODA using the PD process could inactivate about 7 logs of the Staphylococci aureus within 5–10 min and 7 logs of Escherichia coli O157:H7 within 10–30 min, respectively. The addition of quats in N -halamine coatings improved antimicrobial activity against Gram-negative bacteria E. coli O157:H7. However, this result was not observed when the PDC process was applied in coatings because of the increasing hydrophobicity of the coated samples under high coating temperature.

Description: Fiber properties (fiber swelling ability, crystal structure of cellulose, fiber surface morphology, and etc.) of eucalyptus kraft pulp with different contents of carboxyl group in Na-form were studied. There was a direct proportional relationship between water retention value and carboxyl content of pulp. When the carboxyl content increased from 35.6 to 315.7 mmol/kg, tensile index and burst index increased by 56.1 and 117.8 %, respectively, and crystallinity of cellulose decreased by 11.8 %. Environmental scanning electron microscope showed that more fibrillation was observed on the carboxymethylated fiber surface, compared with the control sample. The results from Fourier transform infrared spectra analysis suggested that the relative intensity of the band at 1,633/cm was increased after carboxymethylation treatment, which showed that the carboxyl content increased. The increase in the carboxyl content not only could increase the fiber strength properties, but also could increase the recycling times of the fiber.

Description: This paper demonstrates a way to utilize the rheological properties of high consistency microfibrillated and nanofibrillated cellulose (MFC and NFC) based furnishes for improved dewatering. This is relevant to a new manufacturing platform that is being developed to form composite webs from suitable mixtures of MFC or NFC, traditional pulp fibres and pigments. The studied furnishes were evaluated in the consistencies range of 5–15 % with an MCR 300 rheometer and an immobilization cell. This setup enables us to characterize the rheology of the samples before and during the dewatering process. Classical rheological methods are used to characterise MFC and NFC furnishes. Yield stress as an indicator of the flocculated network strength was found to increase with the consistencies, following the increase in elastic moduli, which indicated a gel-like strongly flocculated matrix. The shear thinning properties of furnishes are observed to follow the Oswald’s rheological model on a wide range of shear rates. It was found that when the MFC and NFC furnishes were dewatered under vacuum conditions, the final solids content was increased with application of shear. This behaviour is more pronounced for furnishes which contained the more swollen NFC (higher WRV, i.e. higher zeta potential). This effect is further exemplified by the change of the complex and dynamic viscosities during the dewatering. The shear rate, the fibre content, and the furnish consistencies were also found to influence the dewatering rate.

Description: Cotton fabrics with antibacterial properties were prepared by the treatment with 3,3′4,4′-benzophenone tetracarboxylic dianhydride (BPTCD) in a combined process of shaking immersion in dyeing machine and pad-dry-cure. Environmentally-benign choline chloride (ChCl)-based deep eutectic solvents (DESs) were mainly examined as treatment media instead of using organic solvent. The results revealed that cotton fabrics treated with BPTCD in urea-ChCl DES showed a strong ester carbonyl peak in fourier transform infrared (FTIR) analysis, indicating fixation of BPTCD on cotton cellulose. Detailed characterizations of the BPTCD-treated cotton were carried out by FTIR, thermogravimetric analysis, scanning electron microscopy, dye staining, and evaluation of hydrophilicity and strength. The treated fabrics demonstrated a high level of antibacterial characteristics before and after UV irradiation. This indicated that addition of ChCl could enhance antibacterial activity of cotton before UV irradiation. Therefore, use of ChCl-based DES along with BPTCD incorporation provided environmentally-acceptable and economically-feasible treatment process for preparation of novel antibacterial cotton.

Description: Rod-like cellulose nanowhiskers and spherical cellulose nanoparticles were prepared from wood-pulp-derived cellulose powder by mechanical refining processes such as high-pressure homogenization (HPH) and ball-milling (BM). The nanowhiskers obtained by the HPH method were found to be 200–500 nm long and 11–16 nm wide. The diameters of the nanoparticles were in the range 40–200 nm, depending on the BM time, and were reduced to 25–50 nm after extra HPH. By adjusting the BM time, cellulose nanoparticles having different polymorphs with similar morphologies were prepared. The X-ray diffraction patterns revealed the recrystallization of cellulose I (1 h of BM time) or cellulose II (4–8 h of BM time) in ball-milled nanoparticles after water washing and solvent exchange treatments. The nanowhisker widths derived from the specific surface areas (SSA) by adsorption methods such as Congo red dye, nitrogen, and water vapor, sorptions were in agreement with those obtained from transmission electron microscopy and atomic force microscopy images. Similar SSA values were obtained for micro- and nano-scale cellulose materials using water vapor adsorption methods, and the SSAs of nanoparticles obtained by different adsorption methods are also discussed.

Description: In this paper, nanofibrillated cellulose/carboxymethyl cellulose (CMC) composite films were prepared using tape casting. The obtained transparent films showed shear induced partial alignment of fibrils along the casting direction, resulting in birefringence in cross polarized light. The carboxyl groups of CMC could be further utilized to create ionic crosslinking by treatment with glycidyl trimethyl ammonium chloride (GTMA). The GTMA treated composite films had improved mechanical properties both in wet and dry state. The chemical composition and morphologies of composites were analyzed with X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy and wide-angle X-ray scattering.

Description: Oil palm empty fruit bunch (EFB) fibers were impregnated by copper nanoparticles (CuNPs) through the cationization process as well as treated by alkali solutions. Mechanical properties of different single fibers were measured and analysed by the Weibull statistical distribution. The weak link scaling of Weibull analysis has provided valuable information to scale the strength of one EFB fiber to predict the strength of other one. The impregnation and interfacial interaction of CuNPs with fibers has been analysed by Fourier transformed infrared spectroscopy, X-ray diffraction study, field emission scanning electron microscopy, energy dispersive X-ray study and thermogravimetric analysis. A significant increase in mechanical property of modified fibers with respect to the control ones has been observed. The crystallinity and thermal stability of the treated fibers were also found to be changed. These findings strongly suggest that CuNPs can be used as an effective reinforcing agent in natural fibers to improve their mechanical property and durability. Graphical Abstract  

Description: Transparent thin film polymer electrolytes were prepared by solvent casting technique with the doping of environmental-friendly ionic liquid, 1-allyl-3-methylimidazolium chloride ([Amim] Cl) into the matrix formed by cellulose acetate (CA) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The ionic conducting nature of this system improves significantly from the order of 10 −7 –10 −2  S cm −1 upon increasing doping of [Amim] Cl content till a maximum of 4.68 × 10 −2  S cm −1 is attained for the composition CA:LiTFSI:[Amim] Cl (14:6:80 wt%). The improving trend in ionic conductivity results from the bond weakening between the connecting atoms in the crystalline region that induces to the increase in amorphous counterpart fractions in the CA matrix. This observation was proved via the accountancies in the reduction of relative viscosity, root mean square value and increase in void as increase in [Amim] Cl doping. The resultant phase conversion hence permits immense lithium ion (Li + ) fluidity along the polymer backbone and assisting the improvement in ionic conductivity. The thin film polymer electrolyte is found to be elastic in the presence of crystalline fraction and radically deforms upon the chains diffusion into the amorphous fraction. The linear curvatures of the Arrhenius plot justify the conductivity improvement as via the increasing frequency of Li + ions hopping as the temperature increases. The increasing addition of [Amim] Cl diminishes both the heat-resistivity and thermal stability of CA:LiTFSI:[Amim] Cl matrix.

Description: A previously unreported nanocomposite (CMC/GO) high-performance film was prepared by a simple solution mixing-evaporation method. The structure, thermal stability, and mechanical properties of the composite films were investigated by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetry analysis, and mechanical testing. The results obtained from these different studies revealed that CMC and graphene oxide were able to form a homogeneous mixture. Compared with pure CMC, the tensile strength and Young’s modulus of the graphene-based materials were improved significantly upon incorporation of 1 wt% graphene oxide by 67 ± 6 % and 148 ± 5 %, respectively. In addition, the DMA composite films also showed a high storage modulus up to 250 °C.

Description: Nano-scaled particles were obtained from two different cellulose acetates, cellulose acetate propionate, and cellulose acetate butyrate using the emulsification solvent evaporation procedure and the low energy methods of solvent displacement (dialysis and controlled precipitation). The relationship between the formulation parameters and the particle properties were evaluated in case of the emulsification-evaporation technique. For the solvent displacement procedures, the influence of the formulation parameters, and the intrinsic polymer properties like the hydrophilic-hydrophobic balance was evaluated. Comparing the methods, it could be shown that large amounts of small and uniform nanoparticles can be obtained by the emulsification solvent evaporation procedure. The solvent displacement techniques turned out to be very easy to use and to yield narrowly distributed particles as well.

Description: A novel quaternarized N -halamine precursor (3-chloro-2-hydroxypropyl)-(5, 5-dimethylhydantoinyl-1-ylmethyl)-dimethylammonium chloride (CDDAC), has been synthesized by a very facile two-step reaction. The two-step synthesis of CDDAC occurred at room temperature with common reactors, so the production of CDDAC could be easily enlarged to an industrial scale. Without any work-up, the final reaction solution which contained CDDAC could be directly used as grafting solution. CDDAC could be effectively grafted onto the surface of cellulose by a dehydrochlorination reaction. CDDAC grafted on cellulose was converted to N -halamine structure which showed powerful antimicrobial property by a chlorination reaction in the diluted NaClO solution. The antimicrobial tests showed that the chlorinated cellulose grafted with CDDAC was capable of 5-log inactivation of S. aureus and E. coli within 5 min. Also, the washing durability and storage stability of chlorinated cellulose grafted with CDDAC were investigated.

Description: Carbonaceous nanofibers (CsNFs) were produced by pyrolysis of cellulose nanofibers synthesised from wood pulp using a top-down approach. The effects of heat treatment conditions on the thermal, morphological, crystal and chemical properties of the CsNFs were investigated using TGA, SEM, XRD and FT-IR, respectively. The results showed that heat treatment conditions around the thermal decomposition temperature of cellulose greatly influence the morphology of resulting materials. Slow heating rates (1 °C/min) between 240 and 400 °C as well as prolonged isothermal heat treatment (17 h) at 240 °C were necessary to avoid destruction of the original fibrous morphology in carbonized nanofibers. On the other hand, such heat treatment had little effect on micron sized fibers. The optimized heat treatment conditions led to the release of oxygen and hydrogen from cellulose before thermal breakdown of glycosidic rings, which in turn prevented depolymerization and tar formation, resulting in the preservation of the fibrous morphology.

Description: Kapok fiber, a natural hollow fiber with thin shell and large cavity, has rarely been used as adsorbent for heavy metal ions. In this paper, kapok fibers were modified with diethylenetriamine pentaacetic acid (DTPA) after hydrophilicity treatment. The adsorption behavior of the resultant kapok-DTPA influenced by pH, adsorption time and initial concentration of metal ion was investigated. The results demonstrate that adsorption equilibrium was reached within 2 min for Pb 2+ and Cd 2+ . Adsorption kinetics showed that the adsorption rate was well fitted by pseudo-second-order rate model. The adsorption isotherms were studied, and the best fit was obtained in the Langmuir model. The maximum adsorption capacities of kapok-DTPA were 310.6 mg g −1 for Pb 2+ , 163.7 mg g −1 for Cd 2+ , 101.0 mg g −1 for Cu 2+ , respectively. After eight desorption and re-adsorption loops, the lost adsorption capacities for Pb 2+ and Cu 2+ were less than 10 %. Because of the large specific area derived from the hollow fiber structure, kapok-DTPA exhibited much better adsorption capacity compared with many other reported adsorbents based on natural materials.

Description: Palladium nano-particles supported on ethylenediamine-functionalized cellulose as a novel bio-supported catalyst were synthesized and characterized. The synthesized catalyst was found to be a highly efficient heterogeneous catalyst for the Heck and Sonogashira couplings in H 2 O as a green solvent at 100 °C in very low loading of Pd. The catalyst could be easily recovered by simple filtration and reused for at least 4 cycles without losing its activity. Graphical Abstract

Description: The consecutive pre-treatment of cellulose with periodate and bisulfite was used as a new potential method to promote nanofibrillation of hardwood pulp and to obtain nanofibrils with sulfonated functionality. Nanofibrils having typical widths of 10–60 nm were obtained from sulfonated celluloses having low anionic charge densities (0.18–0.51 mmol/g) by direct high-pressure homogenization without the use of any mechanical pre-treatments. The aqueous nanofibrils existed as highly viscous and transparent gels and possessed cellulose I crystalline structures with crystallinity indexes of approximately 40 %. A transparent film was obtained from sulfonated nanofibrils having tensile strength of 164 ± 4 MPa and Young’s modulus of 13.5 ± 0.4 MPa. Oxidative sulfonation was shown to be a potential green method to promote nanofibrillation of cellulose, as it avoids the production of halogenated wastes, because the periodate used can be efficiently regenerated and recycled as shown in the preliminary experiments.

Description: Cotton cellulose fibers were modified in inert plasma. Surface morphology of the modified fibers was studied by SEM and changes in the surface composition by XPS and FTIR. Standard goniometry was used for determination of contact angle as a function of modified fiber aging. Absorptivity of modified fibers was determined by gravimetry and fiber width in physiological solution, simulating body liquids, by confocal microscopy. Antibacterial effect of pristine and plasma treated samples was examined by following growth of Escherichia coli . Plasma treatment led to surface ablation, changes in surface morphology and fiber width. Surface of the plasma modified fibers was oxidized and their water absorptivity was reduced. The plasma modification did not affect E. coli growth substantially.

Description: This paper describes an approach to manufacture hierarchical composites from environmentally friendly materials by grafting cellulose whiskers onto regenerated cellulose fibers (Cordenka 700). Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy and X-ray diffraction analysis were performed to verify the degree of modification. The mechanical properties of the unmodified and modified fibers were analyzed using fiber bundle tensile static and loading–unloading tests. To show the effect of cellulose whiskers grafting on the Cordenka fibers, epoxy based composites were manufactured and tensile tests done on transverse uni-directional specimens. The mechanical properties were significantly increased by fiber modification and addition of the nano-phase into composite reinforced with micro-sized fibers.