X. J. Dai, J. S. Church, M. G. Huson

A new fabric with potential in medical textiles has been developed by application of a surface coating on wool using pulsed plasma polymerization of HMDSO. This coating enabled a controllable MVTR and surface adhesion. MVTR in the range recommended for optimum wound healing was obtained by varying frequency, monomer pressure and deposition time. Lower surface adhesion was achieved. Peeling tests, contact angle measurements, SPM force curves and ATR FT-IR were used to characterize the surfaces for both wool and a PE model substrate. All these results were consistent with a decrease in surface energy after PP-HMDSO treatment. ATR FT- IR results showed a siloxane film with less organic Si–(CH₃)ₙ groups and more Si–O–Si cross-links.

S. Weisman, H. E. Trueman, S. T. Mudie, J. S. Church, T. D. Sutherland, V. S. Haritos

Spiders routinely produce multiple types of silk; however, common wisdom has held that insect species produce one type of silk each. This work reports that the green lacewing (Mallada signata, Neuroptera) produces two distinct classes of silk. We identified and sequenced the gene that encodes the major protein component of the larval lacewing cocoon silk and demonstrated that it is unrelated to the adult lacewing egg-stalk silk. The cocoon silk protein is 49 kDa in size and is alanine rich (>40%), and it contains an R-helical secondary structure. The final instar lacewing larvae spin protein fibers of ∼2 μm diameter to construct a loosely woven cocoon. In a second stage of cocoon construction, the insects lay down an inner wall of lipids that uses the fibers as a scaffold. We propose that the silk protein fibers provide the mechanical strength of the composite lacewing cocoon whereas the lipid layer provides a barrier to water loss during pupation.

M. Huson, D. Evans, J. Church, S. Hutchinson, J. Maxwell, G. Corino

Wool fibres have been treated to remove the covalently bound lipid and characterised using lipid analysis, wettability and scanning probe microscopy. A model substrate consisting of alternating stripes of hydrophobic (predominantly CH₃ terminated molecules) and hydrophilic (COOH terminated molecules) surfaces, micro-printed onto a gold-coated mica surface was assessed using the SPM techniques of adhesion, friction and phase imaging and showed that SPM can easily distinguish these surfaces. When KOH/methanol treated wool fibres were examined, SPM showed an increase in coefficient of friction and a decrease in adhesion as the lipid is removed. The increased friction is consistent with studies on the model surface and confirms the hypothesis that the lipid layer decreases the surface friction of fibres. The decreased adhesion is consistent with results in the literature on hair, but is at odds with the results on the model surface. The strong contrast shown between the methyl and carboxylic acid surfaces in the friction image of the micro-patterned surface, and the complete absence of any such contrast developing with time of treatment of the wool fibres strongly suggests that the surface lipid is not present as a discrete outer layer on the fibre. A new model is proposed in which the lipid is intimately associated with the surface proteins and allows for changes in lipid concentration at the surface in response to changes in environmental conditions.

J. S. Church, D. J. Evans

A spectroscopic investigation into the reaction of sodium tetrathionate with cysteine at pH 5 both at the boil and at room temperature has been carried out. The Raman and infrared spectra of the model compounds cysteine, cysteine-S-sulfonate, cysteine-S-thiosulfonate, sodium thiosulfate and sodium sulfite were also obtained and vibrations involving the sulfur atoms were analyzed in detail. These results were utilized in the interpretation of the spectra obtained from tetrathionate–cysteine reaction mixtures. The reaction supernatants were analyzed by high performance thin layer chromatography while the precipitates were analyzed gravimetrically. It was found that during the reaction, the thiol groups of cysteine are oxidised to give predominantly cysteine-S-sulfonate. Cystine was also detected but was determined gravimetrically to be a minor reaction product. No significant amounts of cysteine-S-thiosulfonate were detected. The reaction is accompanied by the formation of elemental sulfur and a small amount of sulfite. Major Reaction pathways are put forth that are consistent with the experimental data.

J. Y. Cai, D. J. Evans, J. S. Church

This paper reports a new application for amineboranes in the bleaching of wool, a typical example of keratin fibre. It has been found in this investigation that amineboranes are unique reductive bleaching agents that do not attack cystine disulphide bonds in wool keratin and do not impart permanent set to the fibre during bleaching. Selected amineborane compounds can be used in conjunction with oxidative agents such as hydrogen peroxide in aqueous media to further enhance the whitening effect and prevent disulphide bond disruption in keratins. The results of this study have suggested that the researched technology outperforms existing bleaching methods on a number of levels and may be an important step towards a new commercial bleaching technology.

B. X. Huang, K. Wang, J. S. Church, Y. S. Li

The combination of electrochemical methods, laser Raman spectroscopy (LRS), surface-enhanced Raman scattering (SERS) and infrared reflection absorption spectroscopy (IRRAS) have been used to demonstrate that a stable passivated film can easily be formed on Nb in 0.15 M NaCl. The composition of the film has been identified to be NbO₂ and different forms of Nb₂O₅. From LRS, the film formed in 0.10 M NaOH has similar composition. A longer exposure of the Nb electrode to air favors the conversion of NbO₂ to the more stable Nb₂O₅ and the transformation of B-Nb₂O₅ to H-Nb₂O₅. In situ analysis of the passivated film in 0.15 M NaCl was carried out by coupling the electrochemical technique with LRS and SERS. The results indicated the presence of different forms of Nb₂O₅ at the metal/solution interfaces.

J. S. Church N. W. Cant D. L. Trimm

The properties of a novel alumina prepared by decomposition of aluminium sulfate at 1000 °C have been investigated. The surface area following heat treatment at 1200 °C is more than a factor of two greater than that of conventional aluminas. Diffuse reflectance infrared spectroscopy measurements show that the types of hydroxyl groups present on the surface of the novel alumina differ from those of a conventional γ-alumina. It appears that the surface of the former may be predominantly of a type which contains aluminium ions in octahedral sites alone. This may be a factor in the enhanced sintering resistance. Inclusion of some rare earth and alkaline earth oxides enhances sintering resistance in the usual way. The extent of improvement correlates with cation size, with La³⁺ and Ba²⁺ showing the greatest effect. Barium loadings of ca. 5 mol-% are required to maximise retained area but X-ray photo-electron spectroscopy measurements show that the near surface Ba/Al ratio does not exceed 0.02. X-ray diffraction patterns of highly loaded samples show the presence of two types of barium aluminate. A barium carbonate-like surface layer is formed on equilibration with air.

J. S. Church, N. W. Cant, D. L. Trimm

The effect of added rare earth and alkaline earth oxides on the resistance of two aluminas to loss of surface area at high temperature has been investigated. In tests of short duration (⩽ 4 h) at 1100 °C, La³⁺ and Ce⁴⁺ are equally effective in reducing loss of area for a commercial γ-alumina. However, in extended tests (24 h) La³⁺ is much more effective than Ce⁴⁺. X-ray diffraction shows that the latter has segregated as CeO₂ and the alumina is largely α-phase. No separate rare earth oxide phase can be observed with La2O3 and θ-alumina is dominant. The same effects are discernable at higher temperature and with a washcoat alumina. Tests with other rare earth oxides and alkaline earth oxides show that an ion size effect is operative. Under severe conditions Ca²⁺, Yb³⁺ and Sm³⁺ are ineffective, Pr³⁺ and Sr²⁺ are moderately effective while La³⁺ and Ba²⁺ are the most effective. Samples containing the latter both exhibit the presence of a hexaaluminate-type phase after tests at 1200 °C. Diffuse reflectance infrared spectroscopy has been used to investigate surface hydroxyl groups formed after reequilibration of samples with ambient air. The groups present on sintered alumina differ only slightly from those on unsintered material. There is a good correlation between hydroxyl group band area, in Kubelka-Munk units, and surface area. Samples with added La₂O₃ and CeO₂ show only AlOH groups which also closely resemble those present on alumina alone. However the band area for oxide stabilised samples appears to be slightly below that for pure alumina of equivalent area. At most 30% of the surface is made up of a capping layer of the added oxide. X-ray photoelectron spectroscopy (XPS ) binding energies, and La/Al and Ce/Al atom ratios determined by XPS, are consistent with the above picture.