Natural Fiber Welding Research Articles

Fiber welded EDTA-modified cellulose for remediation of heavy metal ions

Ethylenediaminetetraacetic acid (EDTA) is a well-known metal chelator and an attractive ligand for covalently modifying adsorbents for bioremediation. Cellulose, a naturally occurring biopolymer, has immense potential as an inexpensive, earth abundant, biocompatible scaffold for EDTA-facilitated environmental remediation; however, pretreatment of the material is required to achieve sufficient degrees of chemical modification. In this study, Natural Fiber Welding (NFW) is used to prepare commercial cotton Aida cloth for EDTA functionalization. Following NFW, the cotton scaffold was covalently modified with up to 0.56 mmol of EDTA per gram of adsorbent, a nearly 2.5-fold increase over native material. The welded EDTA-modified substrates were tested qualitatively against cobalt and quantitatively against nickel, reaching equilibrium binding capacities (qe) of up to 46 mg metal per g of adsorbent, on par with capacities reported from past work on EDTA-modified cellulose. In addition, adsorbent material could be regenerated using mild acid treatment with no significant loss in qe. Unlike the controls, the fiber-welded EDTA-Aida did not fray even after 3 chelation cycles, indicating enhanced textile robustness afforded through NFW treatment. Overall, NFW offers a new approach to converting commercially available, sustainable biomaterials into robust adsorbents for environmental remediation.

Interrogating the Latent Porosity Within Natural Fiber Welded Composites.

Seemingly nonporous biopolymer composites prepared by natural fiber welding (NFW) possess latent pores that can be exfoliated by conscientious solvation. We present a seminal demonstration of this concept for cellulose and explore the impact of latent pores on the manufacture and commercialization of NFW products.

Tunable porosity of cotton xerogels via ionic liquid-based natural fiber welding

Tunable porosity of cotton xerogels via ionic liquid-based natural fiber welding

Incorporation of Functional Extraneous Cellulose in the Natural Fiber Welding Process

The efficient and non-derivatizing dissolution of natural biopolymers by ionic liquids (ILs) is poised to redefine the application of these ubiquitous and structurally robust materials on a grand industrial scale. In concert with this idea is Natural Fiber Welding (NFW), a technique which exploits the solvating properties of ionic liquids to partially dissociate the outer biopolymer layers in strands of fibrous thread, followed by solvent removal to collapse the structures in a reconfigured and entangled hydrogen bonding network. For cotton, this welding produces a layered motif of mesoporous cellulose atop a core of unmodified crystalline cellulose, creating a hierarchical structure which retains a semblance of the native biomaterial. Aggressive welding conditions increase the thickness and surface area of the mesoporous layer, though excessive welding leads to full dissolution of the crystalline core creating a tradeoff between an increase in surface area with loss of product integrity. In the present work, we seek to subvert aggressive welding conditions by supplementing dissolved cellulose as an additive in the welding solution. We will demonstrate how this extraneous cellulose can coat and weld to the underlying cotton substrate to increase the size of the amorphous shell around the crystalline core and, ultimately, bolster the mesoporous network and enhance the overall surface area. In addition, we will discuss how Raman-sensitive functionalization can be used to identify inclusion depth of the extraneous material and as a way to probe the potential for layer-by-layer deposition of functional cellulose during the NFW process.

Time-Dependent Development of Mesoporosity in Ionic Liquid Treated Cellulosic Materials

Natural Fiber Welding (NFW) is process that leverages the unique solvating power of ionic liquids (IL) to mobilize a natural fiber’s outermost polymer strands and enable these mobile polymers to reconfigure and interact with mobilized polymers of adjacent fibers. Upon removal of the ionic liquid via a solvent exchange and drying process, the biopolymer material is welded into a new matrix while still maintaining the vast majority of its native structural hierarchy. Recent work in our laboratory has shown relatively simple modifications to the NFW process can drastically impact the modified matrix morphology, particularly regarding surface structure. Changes in polarity during the solvent exchange process, for instance, can be used to very the surface area over a 1000-fold and produce high surface are materials with tunable mesoporosity. In the present work we investigate the impact of variable ionic liquid treatment time on the development of mesoporosity in fiber welded cotton substrates. Nitrogen gas adsorption/desorption measurements were employed to evaluate changes in surface area and pore size with ionic liquid treatment time. Raman spectroscopy was carried out on epoxy potted material cross sections to assess the impact of treatment time on cellulose decrystallization, and epoxy penetration measured by Raman spectroscopy was used to evaluate the continuity of the mesoporous regions and further asses material porosity.

Antimicrobial Biocomposites Fiber‐Welded with Lignocellulose Containing Silver Nanoparticles

Natural Fiber Welding The anchor is printed on cellulose paper using ionic liquid ink containing silver nanoparticle laden lignocellulose. The study in article number 2100872 by David P. Durkin and co-workers shows how natural fiber welding can transform functional powders into anti-microbial and anti-biofilm textiles, which may be considered for personal protective equipment.

Natural Fiber Welding raises $85 million for biobased fabrics

Natural Fiber Welding raises $85 million for biobased fabrics

Fiber-welded polyionic biocomposites using 1-alkyl-3-vinylimidazolium alkylphosphonate ionic liquids

In this study, imidazolium-based polymerizable ionic liquids (Poly-ILs) were used to prepare novel polyionic biocomposites through Natural Fiber Welding. Two new Poly-ILs containing a 1-alkyl-3-vinylimidazolium cation and an alkylphosphonate anion were synthesized and evaluated for their ability to (i) solubilize a biopolymer (cellulose) matrix and (ii) polymerize with and without dissolved cellulose. Raman spectroscopy and scanning electron microscopy (SEM) were used to characterize the fiber-welded composites. Optimized fiber-welding parameters yielded polyionic biocomposite materials whose physicochemical properties were evaluated using SEM, energy dispersive X-ray spectroscopy (EDS) and water sorption testing in a controlled relative humidity chamber. SEM/EDS revealed polymerized Poly-IL integrated throughout a fiber-welded, polyionic biocomposite matrix; the materials absorbed ca. 38-40 % of their mass in water when exposed to a controlled (70%) relative humidity environment. To reduce the hygroscopic nature of the fiber-welded composites, the methylphosphonate anion was partially exchanged for a more hydrophobic anion (bis-trifluorosufonylimide, TFSI) through a single-pass anion exchange. SEM/EDS of sample cross sections before and after treatment show that this simple anion exchange and rinse procedure delivers up to ca. 5% exchange from methylphosphonate to TFSI. In spite of this low exchange, the water sorption properties of the exchanged polyionic biocomposites were successfully reduced by 14% and could be easily returned to their original dry state at low temperature under vacuum.

Antimicrobial Biocomposites Fiber‐Welded with Lignocellulose Containing Silver Nanoparticles

AbstractBiopolymer materials that use silver to imbue antimicrobial properties are finding broad application in areas such as packaging, textiles, and building materials. Conventional methods to incorporate silver can damage the supporting biopolymer matrix and/or result in large‐sized silver nanoparticles (Ag NPs) with poor antimicrobial efficacy. To mitigate these concerns, in this study, uniformly distributed, small (≈5–10 nm) Ag NPs are grown into a well‐preserved lignocellulose powder matrix by using a gas‐phase reducing agent at low temperature. The Ag NP‐ lignocellulose powders are fully characterized and their antimicrobial performance is investigated by inactivating planktonic bacteria and inhibiting biofilms. The most potent antimicrobial product, L_10Ag, achieves more than 4‐log reduction in planktonic bacterial viability within 3 h and a biofilm inhibition rate of 97.9%. Furthermore, the Ag NP impregnated powders are post‐processed through natural fiber welding (NFW), an emergent, innovative, ionic liquid (IL)‐based method that can be used to engineer biopolymer materials into new functional biocomposites. NFW transforms the powders into higher‐order structures, imparting anti‐microbial capacity without degrading the material properties of the biopolymer support.

10 Start-Ups to Watch 2021: Natural Fiber Welding

10 Start-Ups to Watch 2021: Natural Fiber Welding

Natural Fiber Welding raises $15 million

The plant-based textile firm Natural Fiber Welding (NFW) has raised $15 million from firms including the venture capital arm of BMW. NFW says it will use the money to further scale up production of its leather-like Mirum material and its cotton-like Clarus. Earlier this year, NFW added more than 10,000 m 2 of manufacturing space. With the expanded output, the firm plans to offer its textiles to automakers. NFW’s technology combines plant fibers to make longer strands, enabling better materials properties and eliminating the degradation that normally limits fiber recycling.

Natural Fiber Welding raises $15 million

Natural Fiber Welding raises $15 million

Developing Polyionic Biocomposite Materials through Natural Fiber Welding

Biomaterials such as cotton and silk are abundant natural resources that have demonstrated material properties equal or superior to many synthetic polymers. Using ionic liquids (ILs) and the Natural Fiber Welding (NFW) process, these biomaterials can be chemically and physically enhanced. Here we present our progress on using imidazolium-based polymerizable ionic liquids (Poly-ILs) in the NFW process to prepare polyionic biocomposites. A variety of Poly-ILs with different cation and anion structures were synthesized and subsequently characterized using 1H and 13C NMR. Each Poly-IL was evaluated for its ability to (i) polymerize and (ii) solubilize a biopolymer (cellulose) matrix, revealing anion structural motifs that either limit or enhance a Poly-IL’s ability to polymerize and weld. Optimized parameters yielded polyionic biocomposite materials whose physicochemical properties were evaluated using ATR, SEM and EIS. Figure 1

Developing Polyionic Biocomposite Materials through Natural Fiber Welding

This study presents our progress on using imidazolium-based polymerizable ionic liquids (Poly-ILs) in the NFW process to prepare polyionic biocomposites. Two novel Poly-ILs containing the 1-alkyl-3-vinylimidazolium cation and an alkylphosphonate anion were synthesized and subsequently characterized using NMR. Each Poly-IL was evaluated for its ability to (i) polymerize and (ii) solubilize a biopolymer (cellulose) matrix, and optimized parameters yielded polyionic biocomposite materials whose physicochemical properties were evaluated using ATR-FTIR, RAMAN, and SEM.

Preferential leaching of indium metal during room temperature ionic liquid processing of Pd–In nanoparticle-biopolymer composites

Natural Fiber Welding (NFW) is a green engineering process that uses Ionic Liquids (IL) to prepare functional biocomposites for applications including water purification, energy storage, sensing, and thermal enhancement. The composition of the welding solution can significantly impact welding efficiency as well as the structure and composition of fiber-welded biocomposites. This study evaluates how NFW solvent composition influences metal leaching from lignocellulose fiber-supported Pd–In nanoparticles. Solutions were prepared from pure, dry 1-ethyl-3-methylimidazolium acetate, and controlled amounts of IL contaminants (water, acetic acid), and one molecular co-solvent (acetonitrile). Lignocellulose fibers with embedded Pd–In nanoparticles were welded in each solution and reconstituted in water; the recovered precipitates/filtrates were evaluated using ICP-MS to determine how much palladium and indium leached from each catalyst into the welding solvent. Our data show how excess acetic acid in the NFW solvent causes indium metal to dealloy from Pd–In nanoparticles. Because Pd–In nanoparticles are proven hydrogenation catalysts for water purification, nitrate reduction tests were performed with each fiber-welded product and compared to unwelded control samples. These data show how preferential leaching of indium directly impacted the catalysts nitrate reduction reactivity, and provide insight into how one might control this phenomenon to optimize development of fiber-welded catalyst systems.

Engineering Lignocellulose Fibers with Higher Thermal Stability through Natural Fiber Welding

AbstractThis study reveals how natural fiber welding (NFW) can be used to engineer biopolymer materials with improved thermal stability. First, it is shown how NFW without binders improves lignocellulose yarn thermal stability by ≈17 °C, primarily by condensing microfibril structure. Next, silanized‐cellulose nanofibrils (Si‐CNFs) are developed as NFW binders; this silanization process alters CNF physical and thermal properties. During pyrolysis, Six Oy networks form, which delay CNF decomposition (up to 37 °C), slow cellulose mass loss rates (up to 89%), and can enhance char yield more than twofold. When used as NFW binders, Si‐CNFs increase lignocellulose yarn thermal stability (up to 17 °C) proportional to siloxane amount, and can reduce cellulose mass loss rates (≈25% compared to welding without binder). These exciting results highlight the potential of NFW as a green‐engineering process to transform natural fibers into more thermally stable, biocomposite textile yarns.

Natural Fiber Welding with Novel Ionic Liquids

Natural Fiber Welding (NFW) is a versatile biopolymer manipulation process that uses ionic liquids (ILs) to disrupt the intermolecular interactions between polymer strands. NFW enables the reconfiguration of biopolymer material structure as well as the integration of functional materials within the biopolymer matrix. This process is thought to require ILs that have both chaotropic anions and hydrogen bond donating cations, with past work focusing on ILs that have been shown to be solvents capable of the full dissolution of biopolymer materials (e.g. cotton, silk, linen, and keratin). In the present work, we looked to expand the suite of ILs that could be used for NFW by investigating the impact of IL structure and composition on the NFW process with emphasis placed on studying the impact of cation structure. Fluorescently labeled cotton yarns were exposed to selected ILs under controlled time, temperature, and atmospheric conditions. Confocal fluorescence microscopy and scanning electron microscopy were used to evaluate the level of welding in the IL-treated cotton yarns, and atomic force microscopy and tensile strength testing were used to evaluate changes in the physical properties of the welded yarns. Initial results indicate that NFW may not require the use of an IL with a hydrogen bond donating cation as long as a chaotropic anion is present.

Ionic Liquid Property Effects on the Natural Fiber Welding Process

Natural Fiber Welding (NFW) is a versatile biopolymer manipulation process that uses ionic liquids (ILs) to disrupt the intermolecular interactions between polymer strands, enabling structural reconfiguration. This process is thought to require ILs that have both chaotropic anions and hydrogen bond donating cations, with past work focusing on ILs that have been shown to be solvents capable of the full dissolution of biopolymer materials (e.g. cotton, silk, linen, and keratin). In the present work, we looked to expand the suite of ILs that could be used for NFW by investigating ILs that are not known to be good biopolymer solvents. We looked at how replacing the cation of 1-ethyl-3-methylimidazolium acetate (EMIAc), an IL capable of NFW, with the 1-ethyl-1-methylpyrolidinium cation would impact the welding process. Confocal fluorescence microscopy (CFM) and scanning electron microscopy (SEM) were used to evaluate the level of welding in the IL-treated cotton yarns. We show that NFW may not require the use of an IL with a hydrogen bond donating cation as long as a chaotropic anion is present.

Improving the Thermal Stability of Textile Fibers By Natural Fiber Welding

Natural Fiber Welding (NFW) is an Ionic Liquids (IL) based engineering process that can manipulate biopolymer matrices without destroying their underlying structure. It can be used to incorporate functional materials into the biopolymer matrix. In this study, we evaluate how NFW can be used to improve the thermal stability of natural textile fibers. First, a variety of synthesized and/or commercially available flame-retardant micro/nanomaterials are welded onto the surface of the fibers. Then, using thermogravimetric (TG) analysis, we demonstrate how each coating can enhance the thermal stability of the textile yarn. In some cases, thermal stability improves by as much as 25 °C, primarily through delays in the onset of thermal decomposition and increased char yield. Our data reveal strong potential for NFW to be used to deliver fiber-welded textile yarns with improved thermal stability.

The Impact of Carbohydrate Solutes on the Ionicity of 1-Ethyl-3-Methylimidazolium Acetate Ionic Liquid Solutions

Selected ionic liquids have been shown to be effective solvents for biopolymers. This aspect of ILs has been leveraged in a process called Natural Fiber Welding (NFW) which enables the reconfiguration of biopolymer materials while retaining much of their native structure. Biopolymer dissolution in ionic liquids is largely driven by the interaction of a chaotropic anion and the hydrogen bonds present in biopolymers. This suggests that increasing the concentration of an IL should lead to a greater degree of biopolymer mobilization. However, previous work in our lab has shown that the addition of large mole fractions of polar, aprotic solvents, up to 75 mole-%, can actually increase the degree to which NFW modifies a biopolymer substrate. We have speculated this improvement in the NFW ability of an IL solvent could be the result of the impact of the solvent and/or biopolymer on the anion availability. Ions present in an ionic liquid usually have a high degree of ion aggregation between cations and anions, with 20 to 50% of ions being aggregated. Any anions that are present in such aggregates are less available to interact with biopolymer chains and thus will contribute less to biopolymer mobilization. Ion aggregation can be adjusted through a number of approaches, including changing temperature or introducing a co-solvent to solvate ions. Therefore, the addition of aprotic solvents may, in reality, result in an increase in the availability of anions to disrupt hydrogen bonding, even if the overall concentration of anions actually decreases. The ionic character of a solvent mixture can be characterized by determination of its ionicity. Ionicity is the ratio of diffusion-based estimated ion conductivity to measured ion conductivity, where ionicity values less than unity indicate the presence of ion-aggregation. For highly aggregated ionic liquids, ionicity values less than 0.5 are typical. By monitoring changes in ionicity, the impact of co-solvents and solution on the ionic character of an ionic liquid can be assessed. Changes in ionicity were evaluated for dissolved cellulose, cellobiose, and glucose in 1-ethyl-3-methylimidazolium acetate (EMIAc) and 1:1-mole-ratio mixtures of EMIAc with acetonitrile (1:1 EMIAc:AN) and water (1:1 EMIAc:H2O). Test solutions were made with these three solvent types by dissolving 0.1, 0.5, 1.0, and 3.0 wt.-% of either cotton, microcrystalline cellulose (MCC), cellobiose, or glucose. EMIAc’s ionicity decreased with the 1:1 addition of AN by 27 and 19 % at 20 and 60°C, respectively, and EMIAc’s ionicity increased with the 1:1 addition of H2O by 13 and 22 % at 20 and 60°C, respectively. No significant changes in ionicity were observed with the addition of the carbohydrate solutes. Solutes’ negligible changes to ionicity are consistent with how these solutes produce almost indistinguishable decreases in molar conductivity at given solute content for a given solvent type, suggesting the ion aggregation and conductivity behavior remain unchanged with solute up to 3.0 wt.-%.