Unmodified Cellulose Research Articles

Durability of cementitious materials reinforced with various Kraft pulp fibers

This study was completed to determine the strength, permeability, stability, and interfacial properties of cementitious materials reinforced with engineered Kraft pulp fibers namely, mechanically modified fiber and chemically treated fiber. These two engineered fibers, along with a commercially available unmodified fiber, were used in reinforcing cementitious materials. Test results showed an increase in the permeability characteristics for the reinforced concretes. Hence, these fibres reduced the compressive strength and durability of reinforced concretes as compare to the unreinforced concrete. However, the two engineered fibres performed better than the unmodified fibre in terms of compressive strength, chloride ion permeability and water sorptivity. Further, the drying shrinkage strain was reduced considerably when only 1% chemically treated fiber was added. The study concludes that these two engineered pulp fibers are better alternatives to commercially available unmodified cellulose fibers.

Efficient Adsorption on Benzoyl and Stearoyl Cellulose to Remove Phenanthrene and Pyrene from Aqueous Solution.

Benzoyl and stearoyl acid grafted cellulose were synthesized by a simple chemical grafting method. Using these as chemical adsorbents, polycyclic aromatic hydrocarbons (PAHs), like pyrene and phenanthrene, were effectively removed from aqueous solution. The structural and morphological properties of the synthesized adsorbents were determined through X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA), Fourier transform infrared (FT-IR), FE-SEM, and NMR analyses. Through this method, it was confirmed that benzoyl and stearoyl acid were successfully grafted onto the surface of cellulose. The 5 mg of stearoyl grafted cellulose (St–Cell) remove 96.94% pyrene and 97.61% phenanthrene as compared to unmodified cellulose, which adsorbed 1.46% pyrene and 2.99% phenanthrene from 0.08 ppm pyrene and 0.8 ppm phenanthrene aqueous solution, suggesting that those results show a very efficient adsorption performance as compared to the unmodified cellulose.

High-Strength, High-Toughness Aligned Polymer-Based Nanocomposite Reinforced with Ultralow Weight Fraction of Functionalized Nanocellulose.

Multifunctional lightweight, flexible, yet strong polymer-based nanocomposites are highly desired for specific applications. However, the control of orientation and dispersion of reinforcing nanoparticles and the optimization of the interfacial interaction still pose substantial challenges in nanocellulose-reinforced polymer composites. In this study, poly(ethylene glycol) (PEG)-grafted cellulose nanofibers have demonstrated much better dispersion in a poly(lactic acid) (PLA) matrix as compared to unmodified nanocellulose. Through a uniaxial drawing method, aligned PLA/nanocellulose nanocomposites with high strength, high toughness, and unique optical behavior can be obtained. With the incorporation of 0.1 wt % of the PEG-grafted cellulose nanofibers in PLA, the ultimate strength of the aligned nanocomposite reaches 343 MPa, which is significantly higher than that of other aligned PLA-based nanocomposites reported previously. Moreover, its ultimate strength and toughness are enhanced by 39% and 70%, respectively, as compared to the aligned nanocomposite reinforced with unmodified cellulose nanofibers. In addition, the aligned nanocomposite film is highly transparent and possesses an anisotropic light scattering effect, revealing its significant potential for optical applications.

Cellulose fabric with enhanced water absorbance and permeability using microwave radiation: modeling and optimization by RSM

Body temperature control is one of the most interesting fields in the smart sportswear. Increasing the available hydrophilic sites on the fabric surface is one of the proposed methods for better thermal regulation. In this article, the cellulose fabric’s moisture absorbance capacity was increased by introducing carboxylate groups on the cellulosic fabric using microwave radiation. Response surface methodology was used to optimize the process conditions. Stoichiometric ratio, microwave power, and duration were taken as independent variables; moisture regain and softness were selected as dependent variables. Results show that modification with 1:1 stoichiometric ratio of the reactant to anhydroglucose unit using 1049 W power for 6 min is the optimum condition for obtaining cellulose fabric with highest hydrophilicity and softness. Water vapor permeability as well as static and dynamic contact angle show that the modified fabric is more hydrophilic and transfers vapor better than unmodified cellulose fabric. Also, tensile test shows that this treatment does not affect the mechanical properties of fabrics. Fourier transform infrared spectroscopy and scanning electron microscope were used for fabric characterization.

Cellulose nanocrystals (CNCs) with different crystalline allomorph for oil in water Pickering emulsions

In recent years, nanocelluloses have attracted a lot of interests as promising stabilizers for Pickering emulsion particularly in food, cosmetics and pharmaceutics industries. In this work, two cellulose nanocrystals (named CNCs-I and CNCs-II) with different crystalline allomorph were investigated as stabilizers for oil-water Pickering emulsion. CNCs were prepared by sulfuric acid hydrolysis of unmodified and mercerized microcrystalline cellulose (MCC), respectively. CNCs-I was needle-like particles (length – 200 nm, width – 16.4 nm), while CNCs-II was individual granules (length – 18.8 nm, width – 10.9 nm) with ellipsoid shapes. Both CNCs had surface charge density higher than 0.1 e/nm2. Pickering emulsions stabilized by CNCs-I had larger emulsion ratio, two times smaller droplet size and superior performance of stability than CNCs-II. It is concluded that crystalline allomorph of CNCs played more dominating roles to the stabilization of Pickering emulsion than morphologies of CNCs themselves in this work, and CNCs-II is not the good candidates as stabilizer for Pickering emulsion compared to CNCs-I.

Modulating cell response on cellulose surfaces; tunable attachment and scaffold mechanics

Combining surface chemical modification of cellulose to introduce positively charged trimethylammonium groups by reaction with glycidyltrimethylammonium chloride (GTMAC) allowed for direct attachment of mammalian MG-63 cells, without addition of protein modifiers, or ligands. Very small increases in the surface charge resulted in significant increases in cell attachment: at a degree of substitution (DS) of only 1.4%, MG-63 cell attachment was > 90% compared to tissue culture plastic, whereas minimal attachment occurred on unmodified cellulose. Cell attachment plateaued above DS of ca. 1.85% reflecting a similar trend in surface charge, as determined from ζ-potential measurements and capacitance coupling (electric force microscopy). Cellulose film stiffness was modulated by cross linking with glyoxal (0.3–2.6% degree of crosslinking) to produce a range of materials with surface shear moduli from 76 to 448 kPa (measured using atomic force microscopy). Cell morphology on these materials could be regulated by tuning the stiffness of the scaffolds. Thus, we report tailored functionalised biomaterials based on cationic cellulose that can be tuned through surface reaction and glyoxal crosslinkin+g, to influence the attachment and morphology of cells. These scaffolds are the first steps towards materials designed to support cells and to regulate cell morphology on implanted biomaterials using only scaffold and cells, i.e. without added adhesion promoters.

Paper-based diagnostics in the antigen-depletion regime: High-density immobilization of rcSso7d-cellulose-binding domain fusion proteins for efficient target capture

In this work, we report the development of a general strategy for enhancing the efficiency of target capture in immunoassays, using a bifunctional fusion protein construct which incorporates a substrate-anchoring moiety for the high-abundance immobilization of an antigen-binding domain. This approach was informed by the development of a pseudo first-order rate constant model, and tested in a paper-based assay format using a fusion construct consisting of an rcSso7d binding module and a cellulose-binding domain. These rcSso7d-CBD fusion proteins were solubly expressed and purified from bacteria in high molar yields, and enable oriented, high-density adsorption of the rcSso7d binding species to unmodified cellulose within a 30-second incubation period. These findings were validated using two distinct, antigen-specific rcSso7d variants, which were isolated from a yeast surface display library via flow cytometry. Up to 1.6 micromoles of rcSso7d-CBD was found to adsorb per gram of cellulose, yielding a volume-averaged binder concentration of up to 760μM within the resulting active material. At this molar abundance, the target antigen is captured from solution with nearly 100% efficiency, maximizing the attainable sensitivity for any given diagnostic system.

Enhanced flame-retardant properties of cellulose fibers by incorporation of acid-resistant magnesium-oxide microcapsules

Magnesium oxide (MgO) microcapsules were synthesized via in-situ emulsion polymerization as confirmed by Fourier transform infrared spectroscopy and scanning electron microscopy. Pure MgO and the MgO microcapsules were separately incorporated into cellulose fibers by blend wet spinning. Inductively coupled plasma-emission spectroscopy results revealed that cellulose fibers modified with the MgO microcapsules contained more Mg2+ than those modified by pure MgO, indicating more acid resistance. The flammability and thermal degradation of modified cellulose fibers (cellulose-Mg fibers) were studied by calorimeter (CONE), thermogravimetry (TGA), and the determination of the limiting oxygen index (LOI). The minimal LOI value obtained for the cellulose-Mg fibers was 35, being much higher than that of the unmodified cellulose fiber (19). The heat release rate of the cellulose-Mg fibers was significantly lower than that of the non-doped ones. The TGA curves showed that the generated residues increased from 13.79% (cellulose fiber) to 30.26% (cellulose-Mg fiber).

Rheological behavior of suspensions of modified and unmodified cellulose nanocrystals in dimethyl sulfoxide

The rheological behavior of cellulose nanocrystal (CNC) and modified CNC (mCNC) suspensions in dimethyl sulfoxide (DMSO) was investigated. The efficiency of the surface modification of CNCs by grafting an organic acid chloride to produce hydrophobic CNCs has been verified by X-ray photoelectron spectroscopy (XPS). The thermal degradation temperature of the mCNCs was found to be 165 versus 275 °C for CNCs. The CNC suspensions in DMSO at 70 °C underwent gelation at very low concentration (1 wt%) after 1 day. The network formation was temperature sensitive and did not occur at room temperature. For gels containing 3 wt% CNCs, the complex viscosity at 70 °C increased by almost four decades after 1 day. For the mCNCs in DMSO, a weak gel was formed from the first day and temperature did not affect the gelation. Finally, the effect of adding 10 wt% of polylactide (PLA) to the solvent on the rheological properties of CNC and mCNC suspensions was investigated. The properties of suspensions containing 1.9 wt% CNCs and mCNCs increased during the first and second days, and PLA did not prevent gel formation. However, the reduced viscosity and storage modulus of the CNC and mCNC gels with PLA were lower than those of samples without PLA.

Nanocelluloses obtained by ammonium persulfate (APS) oxidation of bleached kraft pulp (BKP) and bacterial cellulose (BC) and their application in biocomposite films together with chitosan

Abstract Bleached birch kraft pulp (BKP, Södra Cell AB, Sweden) and unmodified bacterial cellulose (BC) pellicles, biosynthesized by the bacterium Komagataeibacter rhaeticus, were converted to cellulose nanofibers via ammonium persulfate (APS) oxidation. Fiber dimensions were investigated in an atomic force microscope, and the crystallite size was calculated by Rietveld analysis. Saos-2 osteosarcoma cell line served to assess the in vitro cytocompatibility of the biocomposite films. Results showed that individual cellulose nanofibers with an average width of 80±15 nm and a length between 600 and 1200 nm are formed by APS oxidation. The obtained BC nanofibers can be promising constituents in nanocellulose films and in chitosan-matrix films with improved physical-mechanical and biological properties. Good cellular biocompatibility was found for chitosan/oxidized cellulose films; the viability of Saos-2 osteosarcoma cells was higher on chitosan/oxidized BC films compared to chitosan/oxidized BKP films.

Nanocoating cellulose paper based microextraction combined with nanospray mass spectrometry for rapid and facile quantitation of ribonucleosides in human urine

A rapid and facile analytical method for quantification of ribonucleosides in human urine was developed by the combination of nanocoating cellulose paper based microextraction and nanoelectrospray ionization-tandem mass spectrometry (nESI-MS/MS). Cellulose paper used for microextraction was modified by nano-precision deposition of uniform ultrathin zirconia gel film using a sol-gel process. Due to the large surface area of the cellulose paper and the strong affinity between zirconia and the cis-diol compounds, the target analytes were selectively extracted from the complex matrix. Thus, the detection sensitivity was greatly improved. Typically, the nanocoating cellulose paper was immersed into the diluted urine for selective extraction of target analytes, then the extracted analytes were subjected to nESI-MS/MS detection. The whole analytical procedure could be completed within 10min. The method was evaluated by the determination of ribonucleosides (adenosine, cytidine, uridine, guanosine) in urine sample. The signal intensities of the ribonuclesides extracted by the nanocoating cellulose paper were greatly enhanced by 136–459-folds compared with the one of the unmodified cellulose paper based microextraction. The limits of detection (LODs) and the limits of quantification (LOQs) of the four ribonucleosides were in the range of 0.0136–1.258μgL−1 and 0.0454–4.194μgL−1, respectively. The recoveries of the target nucleosides from spiked human urine were in the range of 75.64–103.49% with the relative standard deviations (RSDs) less than 9.36%. The results demonstrate the potential of the proposed method for rapid and facile determination of endogenous ribonucleosides in urine sample.

Thermal Stability of Modified Insulation Paper Cellulose Based on Molecular Dynamics Simulation

In this paper, polysiloxane is used to modify insulation paper cellulose, and molecular dynamics methods are used to evaluate the glass transition temperature and mechanical properties of the paper before and after the modification. Analysis of the static mechanical performance of the model shows that, with increasing temperature, the elastic modulus of both the modified and unmodified cellulose models decreases gradually. However, the elastic modulus of the modified model is greater than that of the unmodified model. Using the specific volume method and calculation of the mean square displacement of the models, the glass transition temperature of the modified cellulose model is found to be 48 K higher than that of the unmodified model. Finally, the changes in the mechanical properties and glass transition temperature of the model are analyzed by energy and free volume theory. The glass transition temperatures of the unmodified and modified cellulose models are approximately 400 K and 450 K, respectively. These results are consistent with the conclusions obtained from the specific volume method and the calculation of the mean square displacement. It can be concluded that the modification of insulation paper cellulose with polysiloxane will effectively improve its thermal stability.

Meldrum’s Acid Modified Cellulose Nanofiber-Based Polyvinylidene Fluoride Microfiltration Membrane for Dye Water Treatment and Nanoparticle Removal

The work presented here aims to study and compare the performance of a polyvinylidene fluoride (PVDF) electrospun membrane, unmodified cellulose nanofiber (CNF) based PVDF membrane, and Meldrum’s acid (2,2-dimethyl-1,3-dioxane-4,6-dione) modified CNF-based PVDF membranes against the Fe2O3 nanoparticle filtration and crystal violet (CV) dye adsorption. Herein, we introduced a facile method to produce a unique green adsorbent material from cellulose nanofibers (CNFs) via a nonsolvent assisted procedure using Meldrum’s acid as an esterification agent to enhance the adsorption toward positively charged crystal violet dyes. Most of the surface modifications of cellulose nanofibers have been done using toxic organic solvents like pyridine, dimethyl acetate, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), etc. So far, this is the first report on the surface modification of cellulose nanofibers via a nonsolvent assisted procedure. Both CNF-based PVDF membranes were prepared by successive coating of modified and ...

Photoantimicrobial Biohybrids by Supramolecular Immobilization of Cationic Phthalocyanines onto Cellulose Nanocrystals.

The development of photoactive and biocompatible nanostructures is a highly desirable goal to address the current threat of antibiotic resistance. Here, we describe a novel supramolecular biohybrid nanostructure based on the non-covalent immobilization of cationic zinc phthalocyanine (ZnPc) derivatives onto unmodified cellulose nanocrystals (CNC), following an easy and straightforward protocol, in which binding is driven by electrostatic interactions. These non-covalent biohybrids show strong photodynamic activity against S. aureus and E. coli, representative examples of Gram-positive and Gram-negative bacteria, respectively, and C. albicans, a representative opportunistic fungal pathogen, outperforming the free ZnPc counterparts and related nanosystems in which the photosensitizer is covalently linked to the CNC surface.

High Flux Versus Low Flux Membranes: Adequacy of Hemodialysis

Hemodialysis is the most widely used renal replacement therapy globally1. The dialyzer used in hemodialysis treatment is one of the important determinants of the effectiveness of dialysis 2. Three general types of dialysis membranes are available for hemodialysis procedure: unmodified cellulose (low flux; namely “bio incompatible” membranes), modified/regenerated cellulose (low flux or high flux; namely, “relatively biocompatible”), and synthetic membrane (low flux or high flux; namely “relatively biocompatible”). This study investigates the high flux versus low flux membranes for adequacy of hemodialysis. A total of 40 patients were included in the study of which 28 were males (60%). The mean age of the patients was 42 years. The mean Kt/V was 1.3 ± 0.3 in high flux membrane and 1.2 ± 0.2 in low flux membrane hemodialysis whose differences were statistically significant (P=0.05). The mean of URR was 64.2 ± 10.3 in high flux membrane and 61.1 ± 9.8 in low flux membrane HD whose differences were also statistically significant (P=0.05).

Enhancement of mechanical and electrical performances of insulating presspaper by introduction of nanocellulose

To enhance the insulating performance of presspaper used in power transformers, unmodified nanofibrillated cellulose (UNFC), cationic nanofibrillated cellulose (CNFC), anionic nanofibrillated cellulose (ANFC) and cellulose nanocrystals (CNC) were investigated as the potential nano-additives. Concentration of the nano-additives was 10 wt%. Functional groups and crystallinities of the obtained samples were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Tensile strength, DC volume resistivity, dielectric response and breakdown behavior of the nanomodified and conventional presspaper were analyzed. Results show that nanofibrillated cellulose (NFC) can remarkably enhance tensile strength of insulating presspaper. Compared to ANFC, CNFC has a greater improvement which is mainly ascribed to the electrostatic attraction between the positively charged NFC and negatively charged softwood fiber. In addition to mechanical strength, introduction of nanocellulose can also obviously improve both AC and DC breakdown performances. The reason can be attributed to the reduction of partial discharges inside the composites due to the presence of nanocellulose in the original air voids. Moreover, and importantly, the negative effect of nanocellulose on DC volume resistivity and dielectric response can be neglected. On the basis of the overall performance, we conclude that NFCs are promising nano-additives for insulating presspaper, especially for CNFC.

Surface modified cellulose scaffolds for tissue engineering

We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials. Sheets of bacterial cellulose, grown from a culture medium containing Acetobacter organism were chemically modified with glycidyltrimethylammonium chloride or by oxidation with sodium hypochlorite in the presence of sodium bromide and 2,2,6,6-tetramethylpipiridine 1-oxyl radical to introduce a positive, or negative, charge, respectively. This modification process did not degrade the mechanical properties of the bulk material, but grafting of a positively charged moiety to the cellulose surface (cationic cellulose) increased cell attachment by 70% compared to unmodified cellulose, while negatively charged, oxidised cellulose films (anionic cellulose), showed low levels of cell attachment comparable to those seen for unmodified cellulose. Only a minimal level of cationic surface derivitisation (ca 3% degree of substitution) was required for increased cell attachment and no mediating proteins were required. Cell adhesion studies exhibited the same trends as the attachment studies, while the mean cell area and aspect ratio was highest on the cationic surfaces. Overall, we demonstrated the utility of positively charged bacterial cellulose in tissue engineering in the absence of proteins for cell attachment.

Improvement of thermal stability of insulation paper cellulose by modified polysiloxane grafting

We present a method for improving the thermal stability of insulation paper cellulose. A polysiloxane was grafted to the hydroxyl group connected to the C6 atom in the cellulose chain. The effects of the mass fraction of polysiloxane on the mechanical properties and glass-transition temperatures of model cellulose samples modified by polysiloxane grafting were investigated using molecular dynamics simulations. The results show that for four models, with polysiloxane mass fractions of 0%, 3.3%, 6.5%, and 12.2%, the best chain performance was achieved using a mass fraction of 6.5%. The glass-transition temperature of the modified cellulose with a 6.5% mass fraction of polysiloxane was 48 K higher than that of unmodified cellulose, which shows that modification improved the thermal stability of the cellulose.

Polylactic Acid Bionanocomposites Filled with Nanocrystalline Cellulose from TEMPO-Oxidized Oil Palm Lignocellulosic Biomass

Bionanocomposites from polylactic acid (PLA) filled with unmodified nanocrystalline cellulose from TEMPO-oxidized oil palm empty fruit bunch (OPEFB-NCC) at various loading levels were fabricated using the solvent casting technique. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), attenuated total reflectance Fourier transform infrared spectroscopy (ATF-FTIR), differential scanning calorimetry (DSC), and mechanical analyses were used to characterize the bionanocomposite films. FTIR suggested that the incorporation of the OPEFB-NCC was based on physical interaction. The melting temperature did not change markedly except at higher OPEFB-NCC additions, while the crystallization temperature shifted to lower temperatures and crystallinity increased with increasing OPEFB-NCC content.The SEM of cryo-fractured films indicated a rather weak compatibility between the OPEFB-NCC and PLA, resulting in the decrease of both the modulus and the tensile strength of the bionanocomposite.

Nanostructured and Electroactive Hybrid Films Containing Microcrystalline Cellulose Modified with the Phosphate Group: Synthesis and Characterization

Nanostructured and electroactive hybrid films containing Microcrystalline Cellulose (MC) modified with the phosphate group (MCPO4) and polyaniline (PANI) were prepared using the Layer-by-Layer (LbL) self-assembly technique. In the preparation process of the films cellulose was dispersed in the solution of PANI and the film with PVS/PANI(MCPO4) structure was immobilized on ITO substrate. In order to investigate the influence of the phosphate group on the electrochemical behavior of the film, films were also prepared replacing the modified cellulose (MCPO4) by unmodified cellulose (MC), forming the PVS/PANI(MC) films. Subsequently, all films were characterized by cyclic voltammetry (CV), and the results showed the redox processes characteristic of PANI, but the presence of CMPO4 promotes an increase in the values of current density observed for the PVS/PANI(MCPO4) film when compared to the PVS/PANI(MC) film. This is probably due to a self-doping process of the polymer in the presence of phosphate groups.