Lignocellulosic Micro- And Nanomaterials As Copper Frames For The Evaluation Of The Copper(I)-Catalyzed Azide-Alkyne Cycloaddition

Copper was immobilized onto carboxymethyl cellulose, nanofibrillated cellulose, TEMPO-nanofibrillated cellulose, and lignin. The lignocellulosic frames were used with the aim of providing an effective support for catalyst copper and allowing its further reutilization. Each organic support was successful and effective in the coupling of copper with the exception of lignin. These complexes were used as heterogeneous catalysts to produce 1-benzyl-4-phenyl-1H-1,2,3-triazole from the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) between benzyl azide and phenylacetylene. Each reaction was carried out in water and acetonitrile. Those performed in water were completed in 15 minutes while those done in acetonitrile were allowed to react overnight, reaching completion in less than 20 hours. The yields for Cu-CMC resulted in over 90% for those reactions performed in acetonitrile. All catalysts were easy to recover except Cu-lignin which could not be filtered or extracted from the reaction effluent

Nanofibrillated Cellulose from Appalachian Hardwoods Logging Residues as Template for Antimicrobial Copper

TEMPO nanofibrillated cellulose (TNFC) from two underutilized Appalachian hardwoods, Northern red oak (Quercus rubra) and yellow poplar (Liriodendron tulipifera), was prepared to determine its feasibility to be used as template for antimicrobial metallic copper particles. In addition, a comparison of the TNFC from the two species in terms of their morphological, chemical, thermal, and mechanical properties was also performed. The woody biomass was provided in the form of logging residue from Preston County, West Virginia. A traditional kraft process was used to produce the pulp followed by a five-stage bleaching. Bleached pulps were then subjected to a TEMPO oxidation process using the TEMPO/NaBr/NaClO system to facilitate the final mechanical fibrillation process and surface incorporation of metallic copper. The final TNFC diameters for red oak and yellow poplar presented similar dimensions, 3.8±0.74 nm and 3.6±0.85 nm, respectively. The TNFC films fabricated from both species exhibited no statistical differences in both Young’s modulus and the final strength properties. Likely, after the TEMPO oxidation process both species exhibited similar carboxyl group content, of approximately 0.8 mmol/g, and both species demonstrated excellent capability to incorporate antimicrobial copper on their surfaces

Characterizing the Mechanism of Improved Adhesion of Modified Wood Plastic Composite (WPC) Surfaces

The adhesion properties of the individual components of wood plastic composites (WPCs) are highly relevant to determining their compatibility, and in the case of wood plastic composite boards to determine their potential application as structural components. Preliminary results indicated that WPCs have low surface energy, mainly because of the migration of the lubricant added during processing to the extruded board. Different treatments were performed on the WPC surfaces to increase their wettability, and the treatments included chemical, mechanical and energetic modifications. As a result, the most promising surface treatment regime was a combination between energetic (forced atmospheric plasma treatment, FAPT) and mechanical treatment (sanding) which increased the WPC surface energy up to 40 mJ/m2 . The bondability and delamination properties of bonded WPCs and hybrid WPC-Fiber reinforced plastic (FRP) composites were studied using shear strength and fracture toughness analysis. Bonded WPCs displayed a critical strain energy release rate (Gc) for a crack at the interface 25% to 100% higher when the specimens were mechanically (sanded) and energetically (FAPT) treated. For the hybrid composite samples (WPC-FRP) after the FATP treatment, though was demonstrated than high loads were needed to produce the crack on the interface, no clear trend was found between the compliance (C) and the crack opening length and therefore it was not possible to determine their critical strain energy release rate. The reason for this behavior was most likely because of the high load rate used in the experiments. In terms of the surface analysis of WPC boards and its components, chemical analyses were performed using X-ray photoelectron spectroscopy (XPS), which demonstrated an increase of oxygen on the surfaces after the energetic treatment, and micro- and nano- analysis using atomic force microscopy (AFM). AFM analysis consisted of roughness determinations and adhesion force quantification between surfaces and silicon tips prior and post surface treatment. The AFM analyses were performed both in air and in water and it was demonstrated that interactions with the environment were dramatically avoided when the analysis was performed in water. The adhesion forces for WPC surfaces increased up to 100% after the energetic treatment. Finally, a vapor adsorption surface analysis technique using inverse gas chromatography analysis was used to determine acid-base properties of different components comprising the WPCsto evaluate a potential correlation between the work of adhesion/work of cohesion properties and the final mechanical properties of the composites. The results indicated that for the same kind of filler (assuming same shape and dimensions) mechanical properties of the composites increased when the ratio of work of adhesion/work of cohesion increased as well. For composites prepared with resins of low surface energy no clear trend was found

Nanofibrillated Cellulose and Copper Nanoparticles Embedded in Polyvinyl Alcohol Films for Antimicrobial Applications

Our long-term goal is to develop a hybrid cellulose-copper nanoparticle material as a functional nanofiller to be incorporated in thermoplastic resins for efficiently improving their antimicrobial properties. In this study, copper nanoparticles were first synthesized through chemical reduction of cupric ions on TEMPO nanofibrillated cellulose (TNFC) template using borohydride as a copper reducing agent. The resulting hybrid material was embedded into a polyvinyl alcohol (PVA) matrix using a solvent casting method. The morphology of TNFC-copper nanoparticles was analyzed by transmission electron microscopy (TEM); spherical copper nanoparticles with average size of 9.2 ± 2.0 nm were determined. Thermogravimetric analysis and antimicrobial performance of the films were evaluated. Slight variations in thermal properties between the nanocomposite films and PVA resin were observed. Antimicrobial analysis demonstrated that one-week exposure of nonpathogenic Escherichia coli DH5α to the nanocomposite films results in up to 5-log microbial reduction

Evaluation of Acetaminophen Release from Biodegradable Poly (Vinyl Alcohol) (PVA) and Nanocellulose Films Using a Multiphase Release Mechanism

Biodegradable polymers hold great therapeutic value, especially through the addition of additives for controlled drug release. Nanocellulose has shown promise in drug delivery, yet usually requires chemical crosslinking with harsh acids and solvents. Nanocellulose fibrils (NFCs) and 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)-mediated oxidized nanocellulose fibrils (TNFCs) with poly (vinyl alcohol) (PVA) could be aqueously formulated to control the release of model drug acetaminophen over 144 h. The release was evaluated with a multiphase release mechanism to determine which mechanism(s) contribute to the overall release and to what degree. Doing so indicated that the TNFCs in PVA control the release of acetaminophen more than NFCs in PVA. Modeling showed that this release was mostly due to burst release—drug coming off the immediate surface, rather than diffusing out of the matrix

Observed Kinetic Parameters during the Torrefaction of Red Oak (Quercus rubra) in a Pilot Rotary Kiln Reactor

The torrefaction of red oak (Quercus rubra) was performed in a pilot rotary kiln reactor, and the apparent kinetic results were compared with the results of torrefaction performed in a bench-scale fluidized reactor. Mass loss, gross calorific analyses, ultimate analyses, and proximate analyses were applied to the final torrefied material. The experimental torrefaction temperatures were 250, 275, 300, and 325 °C, and the experimental total torrefaction times were 20, 35, 50, and 80 min. A significant variation of the energy content occurred in the range of temperature between 275 and 300 °C, with the energy yield changing from 97.5% to 83.6%, respectively. The molar ratios H:C:O for the torrefied red oak presented a behavior independent of the experimental equipment when the temperature ranged between 250 and 325 °C. For the torrefaction process of red oak in the pilot rotary kiln reactor, a first-order reaction and one-step kinetic model were fitted with a maximum error of about 7.5% at 325 °C. The observed reaction rate constant (k) for the rotary reactor was 0.072 min−1 at 300 °C, which was 71% lower than the reaction rate constant for torrefied red oak in a bench-scale fluidized reactor. Arrhenius analysis determined an activation energy of 20.4 kJ/mol and a frequency factor of 5.22 min−1. The results suggest significant external heat and mass-transfer resistances in the rotary system

Antimicrobial Properties of the Hybrid Copper Nanoparticles-Carboxymethyl Cellulose

In this study, a simple method to produce a cellulose-based material with antimicrobial properties was developed by introducing copper nanoparticles on carboxymethyl cellulose (CMC) using sodium borohydride as a copper reducing agent. The hybrid material was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). SEM and EDX analysis confirmed the formation of copper nanoparticles within the CMC matrix. TEM indicated a 10- to 20-nm diameter of copper nanoparticles. Antimicrobial properties of the hybrid material were effectively evaluated against the nonpathogenic surrogate of foodborne pathogen Escherichia coli

Lignocellulosic Micro- and Nanomaterials as Copper Frames for the Evaluation of the Copper(I)-Catalyzed Azide-Alkyne Cycloaddition

Copper was immobilized onto carboxymethyl cellulose, nanofibrillated cellulose, TEMPO-nanofibrillated cellulose, and lignin. The lignocellulosic frames were used with the aim of providing an effective support for catalyst copper and allowing its further reutilization. Each organic support was successful and effective in the coupling of copper with the exception of lignin. These complexes were used as heterogeneous catalysts to produce 1-benzyl-4-phenyl-1H-[1,2,3]-triazole from the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) between benzyl azide and phenylacetylene. Each reaction was carried out in water and acetonitrile. Those performed in water were completed in 15 minutes while those done in acetonitrile were allowed to react overnight, reaching completion in less than 20 hours. The yields for Cu-CMC resulted in over 90% for those reactions performed in acetonitrile. All catalysts were easy to recover except Cu-lignin which could not be filtered or extracted from the reaction effluent

Understanding the Affinity between Components of Wood-Plastic Composites from a Surface Energy Perspective

To evaluate surface compatibility in wood-plastic composites (WPCs), the dispersion and acid-base components of surface energy of various thermoplastic resins (matrices) and several wood-based reinforcing materials were determined using inverse gas chromatography (IGC). Polypropylene (PP), nylon 6, poly(ethylene terephthalate) (PET), poly(trimethyl terephthalate) (PTT), high impact polystyrene (HIPS), and styrene maleic anhydride (SMA) were used as thermoplastic resins, while wood flour (hot water extracted and un-extracted), microcrystalline cellulose (MCC) (50 mu m and 90 mu m), alpha-cellulose (60 mu m), and silicified microcrystalline cellulose (SMCC) (60 mu m) were used as reinforcing materials. All matrices and reinforcing components were exposed to low vapor concentrations of apolar (decane, heptane, nonane, octane) and polar (chloroform, ethyl acetate, dichloromethane, acetone, and tetrahydrofuran) probes. Methane and helium were employed as reference and carrier gases, respectively. IGC retention times were used to determine the acid-base component of surface energy of the analyzed materials. The corresponding surface energy, work of adhesion, and work of cohesionwere calculated based on the van Oss-Chaudhury-Good approach (acid-base and Lifshitz-van der Waals interactions). Composite performance was analyzed by measuring tensile and flexural strengths according to ASTM standards. The results indicated that for the same type of filler (assuming similar shape and dimensions), the mechanical properties of the composites increased when the ratio of the work of adhesion to the work of cohesion increased. A similar trend was observed when the thermoplastic resin employed to create the composite possessed an acid-base component of surface energy greater than zero. (c) Koninklijke Brill NV, Leiden, 201