Search

Aquazol [poly(2-ethyl-2-oxazoline)] is a widely used polymeric material for conservation because of its high reversibility and excellent compatibility with various types of material. However, it is hydrophilic and not recommended for use in weight-bearing applications. The objective of this study is to introduce cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) into Aquazol to evaluate the physicomechanical properties of the resultant composites. Several nanocellulose addition formulations involving two types of nanocellulose were designed at various addition levels. Water sorption investigations revealed that the addition of CNCs or CNFs reduced the maximum moisture content of the resultant composites when compared to the unfilled Aquazol. The tensile test results showed that the critical addition level of CNF (2 wt%) is lower than that of CNC (10 wt%) for the nanocellulose to start acting effectively as a mechanically reinforcing agent. Notably, compared with using a single type of nanocellulose for reinforcement, greater reinforcement was observed when both CNCs and CNFs were combinedly added. Field emission scanning electron microscopy indicated that these strong reinforcement outcomes were probably a result of branch-like structures forming among the mixed fillers. The addition of nanocellulose in general resulted in composites having marginally lower thermal stability and optical transparency. In this study, we demonstrated the increased retention of mechanical properties in variously filled composites exposed to anticipated service conditions (55% RH; 23 °C). Crucially, the discoveries in this study indicate that mixed CNC and CNF fillers could be a reasonable option for future applications where lower levels of nanocellulose are desired for optical transparency considerations.

The goal of this study was to examine the conversion of lignin-rich residues from (hard)wood cellulosic sugar production into films without adding binders. Enzymatic hydrolysis was conducted on alkaline pretreated aspen wood to attain saccharification (liberation of monomeric sugars). Non-converted lignin-rich residues in the solid waste stream were fibrillated and formed into films with the aid of micro/nanofibrillated wood (non-saccharified). The films were hotpressed to activate the adhesive characteristic of the lignin in situ. Results showed that hotpressing drastically improved water resistance and wet strength. These effects, not attributable to densification alone, are judged to have arisen from heat-induced hydrolytically stable bonding and hydrophobization. The fully biobased films, even at highly moist (98% RH) conditions, are comparable in strength and stiffness, and tested significantly more biodegradable compared to polystyrene polymer. Overall, this study offers a simple route for converting wood saccharification residues without pre-refining for lignin, thereby favoring cost efficiency of a coproduction strategy in the cellulosic sugar production.

We report herein the use of nanofibrillated cellulose (NFC) for development of enzyme assemblies in an oriented manner for biotransformation with in situ cofactor regeneration. This is achieved by developing fusion protein enzymes with cellulose-specific binding domains. Specifically, lactate dehydrogenase and NADH oxidase were fused with a cellulose binding domain, which enabled both enzyme recovery and assembling in essentially one single step by using NFC. Results showed that the binding capacity of the enzymes was as high as 0.9 μmol-enzyme/g-NFC. Compared to native parent free enzymes, NFC-enzyme assemblies improved the catalytic efficiency of the coupled reaction system by over 100%. The lifetime of enzymes was also improved by as high as 27 folds. The work demonstrates promising potential of using biocompatible and environmentally benign bio-based nanomaterials for construction of efficient catalysts for intensified bioprocessing and biotransformation applications.

In the original publication, the sentence "Similarly, CNFs resulted in a maximum improvement of 262% in the Young’s modulus value and 254% improvement in the σMax value (Table 2).

This research was aimed at fibrillating wood (Aspen) particles using ultra-fine friction grinding, facilitated by a sodium hydroxide pretreatment step. Its objective was to examine the effect of grinding on the extent of fibrillation and the rheological behaviors of the products. The morphology of the ground samples were characterized by optical (OM) and scanning electron microscopy. The extent of fibrillation was evaluated by measurements of particle size distribution (PS), specific surface area, and water retention value. The rheological behavior of the sample suspension was examined by oscillatory and rotational flow testing. Morphological results revealed a reduction in particle size with increasing mechanical fibrillation. The fibrillated samples contained micro- and nano-sized fibers of approximately 50–1000 nm in width, and lengths between hundreds of nanometers to micrometers. Rheological results revealed an increase in storage moduli (G′) and loss moduli (G″) of the fibrillated samples as the grinding was more severe. A shift in the cross-over point (G′ = G″) towards higher strains was also observed, indicating a more stable network structure with a higher extent of grinding. The fibrillated samples showed shear thinning (reduced viscosity) and a decreased thixotropic behavior when subjected to increasing shear rates. A higher extent of fibrillation led to aqueous suspensions of higher shear viscosity, which would also increase when increasing the solid content of the measured suspension. Overall, this study offers a low-cost and simple means for producing fibrillated particles from wood materials, and also benefits their downstream processing through the acquired understanding of their rheological behavior.

The production of cellulosic biofuels often leaves behind solid residues, which can be converted to useful co-products via chemical modification and processing. The objective of this study was to examine the changes in hydroxyl accessibility of a hardwood after the extraction of fermentable sugars (saccharification). Saccharification was performed on milled and dilute-acid pretreated aspen wood and resulted in a glucan-to-glucose conversion of 91%. The unhydrolyzed (solid) fraction was then analyzed for hydroxyl availability using an acetylation method, and the data were related to information of accessible pore volume evaluated using nitrogen adsorption. Different pore volumes were also created by oven-, air-, or freeze-drying of the samples. The results showed that more hydroxyls are available if the physical accessibility (pore volume) of a given substrate is better preserved. Upon saccharification, the accessible hydroxyls were reduced by at least half of that in untreated wood, while the specific pore volume increased 10 times. This finding suggests that future strategies for utilizing saccharification residues for co-products should tap the increased porosity and lower polarity of the substrate.

The fabrication and evaluation of nanocomposites based on microbial cellulose and polyaniline (PANi) are described. Microbial cellulose, so called, bacterial cellulose (BC) was introduced to interfacial polymerization of aniline. Two different phases based on water and chloroform made it easy for nanosized PANi particles to be synthesized on BC. Without any help of a surfactant or templates, BC played a critical role of supporting the growth of PANi. As a function of aniline concentration, the corresponding PANi content and volume resistivity were checked. From morphological images observed by FE-SEM, PANi nanoparticles were densely arrayed along every fiber of BC. The conjugated backbone of PANi was thought to contribute to the improvements of thermal stability of PANi/BC composites. The stiffness and brittleness of PANi were compensated by more ductile BC, suggesting BC can be a promising substrate for it. By the simple and facile interfacial polymerization, the electrical conductivity of PANi/BC composites reached up to 3.8 × 10−1 S/cm when 0.32 M of aniline was used. This PANi/BC nanocomposite can be useful in applications requiring biocompatibility and electrical conductivity such as biological and chemical sensors.

Sheet molding compound is a material com- posed of a polyester thermosetting matrix with a thermo- plastic, an inorganic filler, a metal oxide, reinforcement fibers, and material performance enhancers embedded in the crosslinked matrix. To achieve the optimum mechanical properties required for the composite material, the surface free energy of the polyester composite needs to be under- stood. In this study, the composite matrix and glass rein- forcement fibers are compared with respect to their surface free energy and acid-base characteristics on the basis of inverse gas chromatography measurements. The inverse gas chromatography results for the matrix and glass are compared to previous results found for sized and unsized cellulosic fibers. The inverse gas chromatography data are used to assess chemical modifications performed on the bio- based fibers to predict improvements in the fiber/matrix interaction, and this provides inferences on the overall com- posite cohesion. Our results show first that any fiber rein- forcement system for the polyester composite material has to be acidic to promote good adhesion as the matrix system is very basic and second that the individual dispersive sur- face energies of the components of the matrix interact in a weighted average to determine the overall surface energy of the composite. Also, a commercial glass reinforcement sized for polyester has been found to have a lower interac- tion parameter than literature values for cellulosic fibers. This finding suggests that cellulosic fibers might have an advantage in competing with a conventional glass-fiber reinforcement system in fiber/matrix bonding for sheet molding compound composites. 2008 Wiley Periodicals

The objective of this study was to measure the mechanical properties of individual, native wood fibers using the continuous nanoindentation measurement technique. The indentation depth profile exhibited a small length-scale effect, which was confirmed using the size-effect index derived from the indentation loading curve. The hardness (Hu) or stiffness (Eu) values determined from indentation unloading were also examined for 10 different annual rings of a loblolly pine, with microfibril angles (MFA) between 14� and 36� .A predictable pattern of Eu values was found as a function of MFA, and hence Eu can at least be considered a relative measure of the longitudinal stiffness properties of wood cell walls. For Hu values, a dependence on orientation was observed, and there is a preliminary indication that the dependence could be affected by cell-wall extractives. It is thus desirable, for cell-wall modification studies, to minimize any unintended variations by using samples that are from the same growth ring, so that any treatment-induced changes in the cellwall hardness can be identified. � 2006 Elsevier Ltd. All rights reserved.

This paper attempted to use X-ray photoelectron spectroscopy (XPS) to determine the surface chemistry of wood treated with hydroxymethylated resorcinol (HMR), a coupling agent that enhances the durability of wood adhesive bonding. Wood veneers of hard maple were soaked in HMR solution for either 1, 15, or 30 min. XPS analyses showed that the treated surfaces exhibited an increase in the non-oxidized carbons (C1), a decrease in C–O bonds (C2), and an unaltered or decreased C O or O–C–O bonds (C3), when compared to the control (unsoaked) samples. Despite these findings, the oxygen-to-carbon (O/C) ratios increased with HMR treatments, and the attributes of carbonate species ( CO 3 2 - and HCO 3 - ) were identified. Further analyses revealed that these species were of sodium salts, which also formed in sodium hydroxide (0.08 N) treatment of wood. Overall, this study paves the way for relating the surface oxidation states of the treated wood to the adhesive bond strength, with an ultimate attempt to identify the possible roles of surface chemistry in adhesion durability of wood products.

The objective of this research was to use inverse gas chromatography (IGC) to infer fiber–matrix interactions for predicting practical adhesion between cellulose fibers and polystyrene matrix polymer. IGC experiments were performed on polystyrene, untreated, alkyl- and amino-silanated cellulose (lyocell) fibers. The fiber–matrix acid–base interaction was quantified by (1) pairing the acidic parameter (K A) of one component with the basic parameter (K B) of another component and (2) observing the adsorption enthalpy of the polymer building blocks (ethylbenzene) onto the fibers. Results show that the cellulose/polystyrene acid–base interaction inferred from interaction parameters is closely correlated to that evaluated from the specific adsorption of ethylbenzene. This feature indicates that the acid–base interactions, which play an important role in the adhesion between fibers and polystyrene, can be conveniently predicted from their respective acid and base parameters (K Aand K B) prior to composites' man...

We have developed a two-step method using preadsorbed ethylenediamine (EDA) to catalyze the reaction of (3-aminopropyl)dimethylethoxysilane (APDMES) on silica surfaces. The amount of adsorbed APDMES is nearly twice the amount obtained when the same reaction is performed without the preadsorbed EDA or when monoamines such as propylamine or triethylamine are used instead of EDA. In addition, the use of preadsorbed EDA leads to an increase in the number of chemisorbed APDMES with free aminopropyl groups extending from the surface. Preadsorbed monoamines such as triethylamine, pyridine, or propylamine do not alter the adsorbed amount or change the number of free amine groups extending from the surface because they are easily displaced from the surface by APDMES. Infrared spectroscopy is used to follow the surface reactions on silica powder, and contact angle measurements show that this method also works on glass slides.

This study was aimed at enhancing the mechanical properties of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) using wood microfibers. Ultra-fine friction grinding was conducted on wood particles to reduce their size to the micron scale and to induce fibrillation. Oxidative polymerization was performed on 3,4-ethylenedioxythiophene (EDOT) monomer at seven dosages based on the content of microfibers in the formulation. The presence of PEDOT:PSS in the prepared films was verified by infra-red (IR) spectroscopy and scanning electron microscopy (SEM). The composite films became stronger and stiffer as the fiber content increased. An EDOT:microfibers ratio of 33 wt % was considered the best among the seven tested levels, judging from their low sheet resistivity (340 Ω/sq.) and favorable tensile properties (38 MPa strength and 4.8 GPa stiffness). The selected films were also tested for their resistance to solvents to obtain information about their potential use in different environments. Among the tested solvents, sodium hydroxide greatly decreased the film conductivity. It also had the harshest effect on reducing the weight of the film. Findings from this study demonstrate the successful use of wood microfibers alternative to synthetic substrates and cellulose nanofiber as a supportive and reinforcing material for electrically conductive polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45127.

The objective of this study was to use dynamic contact angle (DCA) analysis and inverse gas chromatography (IGC) to probe the surface-chemical changes in wood pulp fibers during recycling. A simpli...

Renewable biobased carbon fibers are promising materials for large-scale electrochemical applications including chemical processing, energy storage, and biofuel cells. Their performance is, however, often limited by low activity. Herein we report that branching carbon nanotubes can enhance the activity of carbonized cellulosic fibers, such that the oxidation potential of NAD(H) was reduced to 0.55 V from 0.9 V when applied for bioprocessing. Coordinating with enzyme catalysts, such hierarchical carbon materials effectively facilitated the biotransformation of glycerol, with the total turnover number of NAD(H) over 3500 within 5 h of reaction.

Carbon fiber electrodes are greatly promising for microelectronic applications including high performance biosensors, miniaturized transmitters, and energy storage and generation devices. For biosensor applications, one drawback of using carbon fiber microelectrodes, especially single fiber electrodes, is the weak electronic signals, a consequence of low surface area of fibers, which ultimately limit the sensitivity of the sensors. In this paper, we report a novel single fiber microelectrode with branched carbon nanotubes for enhanced sensing performance. The fiber microelectrode was prepared from carbonization of cellulose fibers. Upon introduction of carbon nanotubes, the carbon fibers exhibited a significant increase in the specific surface area from10 to 36.4 m(2)/g (determined by the BET method). A single fiber electrode with such a hierarchical structure was examined for redox reactions of coenzyme NAD(H) which is useful to mediate the assays and transformations of a broad range of biochemicals. Experimental results showed that carbon nanotubes enhanced the redox reactions on surfaces of the electrode by reducing the oxidation potential of NAD(H) from 0.8 to 0.55 V. The single carbon fiber with branched nanotubes was also examined for the detection of glycerol, and the results showed linear responding signals in a concentration range of 40-250 microM. These results are comparable to the properties of fossil-based carbon materials, and thus our cellulose-based carbon electrodes provide a potentially sustainable alternative in bioelectrochemical applications.