Fibrillar collagen structure in ovine leather and related materials and its relationship to strength : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand
Leather is used for a number of products including those of the garment, automotive and
footwear industries. The footwear industry provides a consistent demand for leather.
However, due to strength properties of leather produced from ovine skins, ovine leather is
not currently used in significant quantities in this industry. A greater understanding of the
structure of ovine leather could assist in designing processing steps to increase ovine
leather strength. Fibrillar collagen is a major structural component of a number of tissues
including skin and is the main component of leather. Small angle X-ray scattering (SAXS) is
an X-ray diffraction technique that can be used to investigate fibrillar collagen structure and
A relationship is found between the orientation of collagen fibrils in ovine leather and tear
strength. Stronger leather has a greater alignment of collagen fibrils parallel to the leather
surface while weaker leather has more fibrils out of this plane. The fibrillar collagen
structure is fairly consistent across the entire ovine leather skin, with the relationship
between orientation index and tear strength maintained at all positions investigated. The
fibrillar collagen structure of ovine skins changes during leather processing with the
alignment of collagen fibrils, in the direction parallel to the skin surface, consistently
increasing after the pickling stage.
Significant changes occur to the fibrillar collagen structure of ovine leather during uni-axial
stretching. Initial strain results in reorientation of collagen fibrils followed by stretching of
individual fibrils. The response to strain varies, with stretching of fibrils occurring more
evenly across cross-sections in stronger samples than in weaker samples. The response of a
different collagen rich material, a decellularized extracellular matrix biomaterial, to uni-axial
strain is similar to that of leather.
The findings of this work greatly increase the knowledge of the fibrillar collagen structure
of ovine leather. Through this work a fundamental relationship between fibrillar collagen
orientation and tear strength has been identified. The results of this work can be used to
develop appropriate processing techniques to create leather with desired characteristics.
The knowledge gained in this work is applicable to leathers produced from different
species and may extend to other processed collagen rich tissues and tissue products.