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Basil-Jones M.M.,The New School | Edmonds R.L.,Leather and Shoe Research Association | Allsop T.F.,Massey University | Cooper S.M.,Leather and Shoe Research Association | And 5 more authors.
Journal of Agricultural and Food Chemistry | Year: 2010

SAXS has been applied to structural determination in leather. The SAXS beamline at the Australian Synchrotron provides 6 orders of magnitude dynamic range, enabling a rich source of structural information from scattering patterns of leather sections. SAXS patterns were recorded for q from 0.004 to 0.223 Å-1. Collagen d spacing varied across ovine leather sections from 63.8 nm in parts of the corium up to 64.6 nm in parts of the grain. The intensity of the collagen peak at q = 0.06 Å-1 varied by 1 order of magnitude across ovine leather sections with the high-intensity region in the corium and the low intensity in the grain. The degree of fiber orientation and the dispersion of the orientation has been quantified in leather. It is shown how the technique provides a wealth of useful information that may be used to characterize and compare leathers, skin, and connective tissue. © 2010 American Chemical Society. Source

Wells H.C.,Massey University | Holmes G.,Leather and Shoe Research Association | Haverkamp R.G.,Massey University
Journal of the American Leather Chemists Association | Year: 2016

The processing of bovine hides to leather results in a significant proportion of defective leather known as loose leather. It has not previously been possible to recognize hides that may produce loose leather. Hides were processed through to leather with samples retained at the pickle, wet blue and crust leather stages with material that resulted in loose leather compared with that resulting in tight leather, using ultrasonic imaging. The loose precursor is characterized by a lower density of material in the mid grain layer. The looseness is quantified by amplitude differences in ultrasound line scans or cross-sectional area scans between loose leather and tight leather with 2-4 times the amount of low intensity area in loose leather at all three process stages. This enables detection of hides that will result in loose leather and may enable unsuitable hides to be diverted to other process streams to save substantial processing costs. Source

Basil-Jones M.M.,Massey University | Edmonds R.L.,Leather and Shoe Research Association | Norris G.E.,Massey University | Haverkamp R.G.,Massey University
Journal of Agricultural and Food Chemistry | Year: 2012

The distribution and effect of applied strain on the collagen fibrils that make up leather may have an important bearing on the ultimate strength and other physical properties of the material. While sections of ovine and bovine leather were being subjected to tensile strain up to rupture, synchrotron-based small-angle X-ray scattering (SAXS) spectra were recorded edge-on to the leather at points from the corium to the grain. Measurements of both fibril orientation and collagen d spacing showed that, initially, the fibers reorient under strain, becoming more aligned. As the strain increases (5-10% strain), further fibril reorientation diminishes until, at 37% strain, the d spacing increases by up to 0.56%, indicating that significant tensile forces are being transmitted to individual fibrils. These changes, however, are not uniform through the cross-section of leather and differ between leathers of different strengths. The stresses are taken up more evenly through the leather cross-section in stronger leathers in comparison to weaker leathers, where stresses tended to be concentrated during strain. These observations contribute to our understanding of the internal strains and structural changes that take place in leather under stress. © 2012 American Chemical Society. Source

Wells H.C.,Massey University | Edmonds R.L.,Leather and Shoe Research Association | Kirby N.,Australian Synchrotron | Hawley A.,Australian Synchrotron | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2013

The main structural component of leather and skin is type I collagen in the form of strong fibrils. Strength is an important property of leather, and the way in which collagen contributes to the strength is not fully understood. Synchrotron-based small angle X-ray scattering (SAXS) is used to measure the collagen fibril diameter of leather from a range of animals, including sheep and cattle, that had a range of tear strengths. SAXS data were fit to a cylinder model. The collagen fibril diameter and tear strength were found to be correlated in bovine leather (r2 = 0.59; P = 0.009), with stronger leather having thicker fibrils. There was no correlation between orientation index, i.e., fibril alignment, and fibril diameter for this data set. Ovine leather showed no correlation between tear strength and fibril diameter, nor was there a correlation across a selection of other animal leathers. The findings presented here suggest that there may be a different structural motif in skin compared with tendon, particularly ovine skin or leather, in which the diameter of the individual fibrils contributes less to strength than fibril alignment does. © 2013 American Chemical Society. Source

Edmonds R.L.,Leather and Shoe Research Association
XXXIII IULTCS Congress | Year: 2015

In this work, a mathematical model of leather fibre reorientation during strain was developed in order to improve understanding of the stress strain processes occurring at fibre level within the bulk of a fibrous sheet. The model consisted of parameters including, fibre density, fibre diameter, fibre angle, fibre arc length, fibre chord length, and D-spacing spring constant. A number of different mechanisms for the reorientation and strain of individual fibres were examined and compared to real data. After a number of refinements, a mechanistic model that fit the data was found as follows. In the model, the sheet of leather was assumed to be composed of discrete fibres fixed in space at each end with a defined initial angle between those ends and a corresponding chord length and separate arc length between the two ends. During strain, the fibres are stretched in a way that takes up slack in the fibre arc length until it equals the chord length then the taught-straight fibre reorients towards the direction of strain, and finally fibres stretch with an associated shift in the measured d-spacing. Model predictions were compared to real measured changes in fibre reorientation and strain during bulk strain and found to fit the data well. The mechanism for reorientation and fibre strain developed in this work can now assist in the development of statistical mechanistic models that describe bulk properties of leather, such as tear strength, based on the properties of the intrinsic fibres. Source

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