J. S. Church, D. J. Evans

Two contrasting infrared spectroscopic techniques, Attenuated Total Reflectance (ATR) and PhotoAcoustic Spectroscopy (PAS), have been investigated as means for the determination of fluorocarbon polymer finishes on wool fabric. Based on the experimental conditions used, the results of the PAS method are more characteristic of the bulk sample, while the ATR results are more surface specific. Linear calibrations between polymer add-on, as determined by total fluorine analysis, and the absorbance of the C-F stretching bands of the normalized spectral data were obtained for a typical commercial fluorocarbon polymer. The correlation obtained for the PAS method was found to be significantly better than that of the ATR method. The lower limit of detection of fluorocarbon polymers on wool using the PAS technique was 0.25% on the weight of the wool (oww). In contrast, fluorocarbon polymer add-ons as low as 0.125% oww (approximating monolayer coverage) could be analyzed using the ATR method. At high levels of add-on, the ATR calibration deviated from linearity. This can be attributed to the distribution of fluorocarbon polymer on the surface of the fiber, in particular, the build up of polymer on the cuticle cell edge regions. The quantitative methods developed are used to help access the effects of wear and the subsequent heating of fluorocarbon polymer-treated fabric samples.

J. S. Church, J. R. Durig, T. A. Mohamed, A. B. Mohamed

The IR spectra of gaseous and solid hexamethyldisilane between 4000 and 25 cm⁻¹ and the far-IR spectrum of the liquids from 450 to 25 cm⁻¹ have been recorded. The Raman spectra have been recorded from 3500 to 10 cm⁻¹ for all three physical phases. Assisted by ab initio calculations, the vibrational spectrum of hexamethyldisilane has been assigned under D_3d symmetry and the results of a normal coordinate analysis are discussed. No spectral features indicative of free internal rotation have been observed. Gradient ab initio calculations have been carried out for the disilane and hexamethyldisilane molecules using different types of basis sets. The structural parameters, rotational constants, unscaled and scaled frequencies and harmonic force constants have been reported for both disilane and hexamethyldisilane.

J. S. Church, A. S. Davie, D. W. James, W. H. Leong, D. J. Tucker

A new cell has been developed for the measurement of fiber and textile samples using FT-Raman spectroscopy. It improves the strength of the signal over that of conventional solid cells by the compression of the samples to be analyzed and the use of a mirror to reflect scattered radiation back out of the cell and into the collection lens of the spectrometer. The new cell also eliminates the problem of cell window material interfering with the sample spectrum, since the laser passes through a windowless aperture to reach the sample. This consideration is particularly important when spectra are being obtained from weakly scattering samples. The design, optimization, and use of the new cell are presented. The performance of the new cell in terms of improvements in signal-to-noise ratio and elimination of spectral artifacts is compared to that of other conventional sampling techniques. Significant improvements in spectral quality were obtained from both natural and synthetic fiber and textile samples.

J. S. Church, A. S. Davie, D. W. James, W. H. Leong, D. J. Tucker

A Raman spectroscopic method for the determination of wool wax content in raw wool has been developed. The analyses were performed on 250-mg wool samples by using a spectral component band resolution method. The method has a moderate sample throughput rate, is non-destructive and does not require the use of solvents. Samples ranging between 0.5 and 31% (w/w) wool wax were analyzed. The results obtained were compared with those obtained by a solvent extraction method. If the nonextractable lipid content of the wool is considered, the results of the Raman spectral and extraction methods were in excellent agreement. From a practical standpoint, the minimum detection limit of the method is 3% wax. In general, the precision of the Raman spectroscopic method was better than that obtained for the extraction method.

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.

E. A. Carter, P. M. Fredericks, J. S. Church, R. J. Denning

The FT-Raman spectrum of wool has been obtained using near-IR excitation. No significant fluorescence was observed and the spectra could be obtained routinely. No sample damage was observed for laser powers up to 400 mW. Several methods of sample presentation for both wet and dry wool were investigated and the optimum data collection conditions were determined for each. Dry dense plugs of wool fibers (∼0.16 g cm⁻³) were found to provide the best spectra. Due to improvements in band resolution and signal-to-noise ratio, several previously unobserved spectral features in the wool spectrum have become apparent. The assignment of the Raman-active vibrational modes of wool are reviewed and updated to include these features. Raman spectra obtained from chlorinated and untreated wool samples did not exhibit any significant differences. In contrast, the ATR spectra obtained from these samples exhibited significant differences in the S-O stretching region.

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.

J. R. Durig, J. S. Church, C. M. Whang, R. D. Johnson, B. J. Streusand

The infrared (3500 to 20 cm^-1) and Raman (3500 to 10 cm^-1) spectra have been recorded for both the gaseous and solid phases of CH₃CH₂PF₂ and CD₃CD₂PF₂. Additionally, the Raman spectra of the liquids were recorded and qualitative depolarization values were obtained. All of the normal modes of the trans conformer except the CH₃ torsion have been assigned based on band contours, depolarization values, and group frequencies. In the spectra of the fluid phases, several of the PF₂ modes as well as the CH₃ torsion have been observed for the gauche conformer, but only the trans conformer exists in the solid state. A normal coordinate calculation has been carried out by utilizing a modified valence force field to calculate the frequencies and the potential energy distribution. The barriers to methyl rotation of the gauche conformer for the -d₅ molecule and for the -d₃ molecule were determined to be 885 cm^-1 (2.53 kcal/mol) and 902 cm^-1 (2.58 kcal/mol), respectively. From a temperature study of the Raman spectrum of the gas, an enthalpy difference of 56 ± 22 cm^-1 (160 ± 62 cal/mol) was obtained with the trans conformer being more stable. Similar studies of the liquid gave an enthalpy difference of 96 ± 12 cm^-1 (275 ± 33 cal/mol) also with the trans conformer more stable. From the observed difluorophosphino torsional data, a potential function for the trans to gauche interconversion of CH₃CH₂PF₂ is suggested. Most of the fundamentals appear as doublets in the spectrum of the solid which indicates that there are at least two molecules per primitive cell. All these results are compared to similar quantities for some corresponding molecules.