Luke M. Haverhals

Process variables that control natural fiber welding: time, temperature, and amount of ionic liquid

A systematic study of variables that affect the fiber welding process is presented. Cotton cloth samples are treated with controlled amounts of 1-ethyl-3-methylimidazolium acetate for a series of times and temperatures. Diluting the ionic liquid with a volatile molecular co-solvent allows temporal and spatial control of the welding process not possible with neat ionic liquids. Materials are characterized by scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and mechanical (tensile) testing. Results suggest careful management of process variables permits controlled, reproducible manipulation of chemical and physical properties.

Fluorescence monitoring of ionic liquid-facilitated biopolymer mobilization and reorganization.

Ionic liquid-facilitated mobilization and reorganization of biopolymers in natural fibrous materials is visualized by confocal fluorescent spectromicroscopy. Ionic liquid-based processes controllably fuse adjacent fibres while simultaneously leaving selected amounts of biopolymers in their native states. These processes generate congealed materials with extended intermolecular hydrogen bonding networks and enhanced properties.

Concurrent zero-dimensional and one-dimensional biomineralization of gold from a solution of Au3+ and bovine serum albumin

Abstract A technique was developed for preparing a novel material that consists of gold nanoparticles trapped within a fiber of unfolded proteins. These fibers are made in an aqueous solution that contains HAuCl4 and the protein, bovine serum albumin (BSA). By changing the ratio of gold to BSA in solution, two different types of outcomes are observed. At lower gold to BSA ratios (30–120), a purple solution results after heating the mixture at 80 °C for 4 h. At higher gold to BSA ratios (130–170), a clear solution containing purple fibers results after heating the mixture at 80 °C for 4 h. UV–Vis spectroscopy and light scattering techniques show growth in nanocolloid size as gold to BSA ratio rises above 100. Data indicate that, for the higher gold to BSA ratios, the gold is sequestered within the solid material. The material mass, visible by eye, appears to be an aggregation of smaller individual fibers. Scanning electron microscopy and transmission electron microscopy indicate that these fibers are primarily one-dimensional aggregates, which can display some branching, and can be as narrow as 400 nm in size. The likely mechanism for the synthesis of the novel material is discussed.

Characterization of Polymer Movement in Fiber Welded Cellulose Composites

Ionic liquids are effective solvents for the dissolution of biopolymers such as cellulose and silk. New materials can be created from these natural feedstocks by processes that involve the full dissolution of biomaterials. Many reports show that the dissolution and reconstitution processes eliminate the native polymer structure, often with deleterious consequences to the physical properties of the material. Recently, it has been shown that robust biopolymer based structures may be created without full dissolution of the material by a method we call “Natural Fiber Welding”. The welding process generates modified natural fiber structures while leaving much of the material in its native state. As a result, natural fiber welding enables tunable preservation of native microstructure while also affording manipulation of important material properties.

Lignocellulosic Composites Prepared Utilizing Aqueous Alkaline/Urea Solutions with Cold Temperatures

Lignocellulosic composites (LCs) were fabricated by partially dissolving cotton to create a matrix that was reinforced with osage orange wood (OOW) particles and/or blue agave fibers (AF). LCs were composed of 15–35% cotton matrix and 65–85% OWW/AF reinforcement. The matrix was produced by soaking cotton wool in a cold aqueous alkaline/urea solvent and was stirred for 15 minutes at 350 rpm to create a viscous gel. The gel was then reinforced with lignocellulosic components, mixed, and then pressed into a panel mold. LC panels were soaked in water to remove the aqueous solvent and then oven dried to obtain the final LC product. Several factors involved in the preparation of these LCs were examined including reaction temperatures (−5 to −15°C), matrix concentration (15–35% cotton), aqueous solvent volume (45–105 ml/panel), and the effectiveness of employing various aqueous solvent formulations. The mechanical properties of LCs were determined and reported. Conversion of the cotton into a suitable viscous gel was critical in order to obtain LCs that exhibited high mechanical properties. LCs with the highest mechanical properties were obtained when the cotton wools were subjected to a 4.6% LiOH/15% urea solvent at −12.5°C using an aqueous solvent volume of 60 ml/panel. Cotton wool subjected to excessive cold alkaline solvents volumes resulted in irreversible cellulose breakdown and a resultant LC that exhibited poor mechanical properties.

Ionic Liquid-Facilitated Preparation of Lignocellulosic Composites

Lignocellulosic composites (LCs) were prepared by partially dissolving cotton along with steam exploded Aspen wood and burlap fabric reinforcements utilizing an ionic liquid (IL) solvent. Two methods of preparation were employed. In the first method, a controlled amount of IL was added to preassembled dry matrix of cotton and Aspen wood with a burlap weave reinforcement. In the second method, IL solvent, cotton, and Aspen wood were mixed to produce a thick paste matrix that was subsequently pressed into the burlap weave reinforcement. The IL-based solvent was removed via water soaking, and the flexural and tensile properties of the LCs were examined. In this study, the matrix paste method produced a superior LC. Variables such as processing time (IL interaction time) and fabric weaves were found to influence the mechanical properties of the LCs. Although significant process optimization can still be realized, the mechanical properties of several of the LCs fabricated in this study were comparable to injection molded test specimens of neat high density polyethylene or neat polypropylene.