Q. Li, J. S. Church, A. Kafia, M. Naebe, B. L. Fox

The homogeneous and stable dispersion of carbon nanotubes (CNTs) in solvents is often a prerequisite for their use in advanced materials. Dispersion procedures, reagent concentration as well as the interactions among reagent, defective CNTs and near-perfect CNTs will affect the resulting CNT dispersion properties. This study, for the first time, presents a detailed comparison between two different approaches for dispersing CNTs. The results enhance our understanding of the interactions between surfactant, defective CNTs and near-perfect CNTs and thus provide insight into the mechanism of CNT dispersion. Dispersions of ‘‘as-produced’’ short multi-walled carbon nanotubes (MWCNTs) in N,N-imethylformamide were prepared by two different surfactant (Triton X-100) assisted methods: ultrasonication and ultrasonication followed by centrifugation, decanting the supernatant and redispersing the precipitate. Visual observation and UV–visible spectroscopy results showed that the latter method produce a more stable dispersion with higher MWCNT content compared to dispersions produced by ultrasonication alone. Transmission electron microscopy and Raman spectroscopic investigations revealed that the centrifugation/decanting step removed highly defective nanotubes, amorphous carbon and excess surfactant from the readily re-dispersible near-perfect CNT precipitate. This is contrary to other published findings where the dispersed MWCNTs were found in the supernatant. Thermogravimetric analysis showed that 95 % of Triton X-100 was removed by centrifugation/ decanting step, and the remainder of the Triton X-100 molecules is likely randomly adsorbed onto the MWCNT surface. Infrared spectral analysis suggests that the methylene groups of the polyoxyethylene (aliphatic ether) chains of the residual Triton X-100 molecules are interacting with the MWCNTs.

J. S. Church, A. L. Woodhead, A. A. Walker, T. D. Sutherland

Raspy crickets produce silk webs that are used to build shelters. These webs have been found to consist of both fiber and film components. Raman spectra obtained from both components were found to be very similar for a given species. The protein structure of the fibers and films produced by both species was predominately β-sheet with lesser amounts of β-turns, unordered and α-helical protein also detected. The orientation of the β-sheet backbone in the fiber was determined to be parallel to the fiber axis. Compared to cocoon and dragline silk the orientation distribution exhibits a significant randomly orientated protein component. Amino acid analysis confirmed the presence of glycine, serine, and alanine in both species, which are known to form antiparallel β-sheet structures. Both species, although at significantly different concentrations, where found to contain proline. This amino acid is uncommon in insect silks, and likely involved in increasing fiber elasticity.

J. Y. Cai, J. Min, M. Miao, J. S. Church, J. McDonnell, R. Knott, S. Hawkins, C. Huynh

Multiwall carbon nanotube (CNT) spun yarns were subjected to γ-irradiation in an oxygen rich environment, followed by the application of epoxy to form CNT/epoxy composite yarns with a high CNT fraction. The method for fabrication of the CNT/polymer composite yarns was presented, and the effect of γ-irradiation on the mechanical performance of the pure CNT spun yarns and their epoxy composite yarns were studied. The γ-irradiated CNT yarns were also characterized by X-ray Photoelectron Spectroscopy and Raman spectroscopy. The results of this study have demonstrated that the γ-irradiation is an effective micro-engineering tool to improve mechanical properties of the CNT spun yarn and its epoxy composite yarn.

J. Y. Cai, J. McDonnell, C. L. Francis, J. S. Church, J. Tsanaktsidis, J. Chiefari

This paper reports a facile method for protecting keratin fiber with water soluble N-substituted maleimides during high temperature processing in aqueous solutions. Three water soluble N-substituted maleimides, including aliphatic and aromatic maleimides, were synthesized and applied. Their treatment effects were characterized by Raman spectroscopy and evaluated on the fiber’s physical and mechanical properties. An aliphatic maleimide, 3-maleimidopropanoic acid, was demonstrated to be an excellent protective agent for keratin fiber, as evidenced by the significantly reduced permanent set and improved wet burst strength of the protected substrate.

A. Walker, J. S. Church, A. L. Woodhead, T. D. Sutherland

Silks are semi-crystalline solids in which protein chains are associated by intermolecular hydroge bonding within ordered crystallites, and by entanglement within unordered regions. By varying the type of protein secondary structure within crystallites and the overall degree of molecular order within fibers, arthropods produce fibers with a variety of physical properties suited to many purposes. We characterized silk produced as a tactile stimulus during mating by the grey silverfish (Ctenolepisma longicaudata) using Fourier transform infrared spectroscopy, polarized Raman spectroscopy, gel electrophoresis and amino acid analysis. Fibers were proteinaceous- the main component being a 220 kDa protein- and were rich in Gln/Glu, Leu, and Lys. The protein structure present was predominantly random coil, with a lesser amount of beta-structure. Silk fibers could readily be solubilized in aqueous solutions of a mild chaotrope, sodium dodecyl sulfate, indicating protein chains were not crosslinked by disulfide or other covalent bonds. We conclude that entanglement is the major mechanism by which these silk proteins cohere into a solid material. We propose silks used as short-term tactile cues are subject to less stringent requirements for molecular order relative to other silks, allowing the random coil structure to be favored as an adaptation promoting maximal entanglement and adhesion.

M. H. J. van der Sluijs, J. S. Church

Quarantine treatments of raw cotton fiber with gamma irradiation are known to have an adverse effect on fiber properties and thus could have an effect on processing into textile products. In this study, the effects of such irradiation treatments on two different cottons, cultivars of Upland and Extra Long Staple, were studied. Even at low dosages, gamma irradiation affects the physical properties of the fiber, with these effects becoming more apparent and significant as the dosage increased. While the affect on moisture regain was marginal, dye affinity was adversely affected. From a textile processing performance and quality point of view, the irradiation dosages did not have a significant impact on the yarn evenness and imperfection values, but did have a significant effect on yarn strength and elongation, as well as fabric strength and abrasion resistance. The degradation of these properties could have a significant to catastrophic effect on product durability.

J. Poole, J. S. Church, A. L. Woodhead, M. Huson, A. Sriskantha, I. L. Kyratzis, T. D. Sutherland

Flexible and solvent stable fibers are produced after concentrated recombinant honeybee protein solutions are extruded into a methanol bath, dried, drawn in aqueous methanol, then covalently cross-linked using dry heat. Proteins in solution are predominantly coiled coil. Significant levels of non-orientated β-sheets form during drying or after coagulation in aqueous methanol. Drawing generally aligns the coiled coil component parallel with the fibre axis and β-sheet component perpendicular to the fiber axis. The fibres are readily handled, stable in the strong protein denaturants, urea and guanidinium, and suitable for a range of applications such as weaving and knitting.

R. L. Long, M. P. Bange, C. D. Delhom, J. S. Church, G. A. Constable

Knowing the yarn-strength performance potential of cotton fibre is advantageous to spinners during mill preparation, and to researchers developing new genotypes and management strategies to produce better fibre. Standard High Volume Instrument (HVI) fibre quality attributes include micronaire (a combined measure of fibre linear density and maturity) and bundle tensile properties. While these attributes relate well to yarn strength, alternative fibre quality attributes may better explain the variation in yarn strength. Two field experiments over two seasons were conducted to assess the fibre and yarn performance of some Australian cotton genotypes. The aim was to assess and compare alternative measures for micronaire, and to compare bundle and single-fibre tensile measurements, and assess the relative yarn-strength predictive performance of these attributes. Specific fibre measurement comparisons were for linear density (double-compression Fineness Maturity Tester (FMT) and gravimetric), maturity ratio (FMT, polarised light, calculated, and cross-sectional), and tensile properties (HVI bundle and Favimat Robot single fibre). Multiple linear regression models for yarn strength that included yarn manufacturing variables and standard HVI fibre quality parameters performed well (standard error of prediction (SEP) 2.40 cN tex^–1). Multiple linear regression models performed better when alternatives to micronaire were used, e.g. using gravimetric linear density (SEP, 2.15 cN tex^–1) or laser photometric determined ribbon width (SEP 1.71 cN tex^–1). Yarn strength models were also better when single fibre tensile properties were substituted for bundle tensile properties (SEP 1.07 cN tex^–1). The substitution of alternative fineness variables for micronaire or single-fibre strength for bundle strength in a simple fibre quality index also improved the prediction of yarn strength.