A small angle X-ray scattering study of the structure and development of looseness in bovine hides and leather.

Background: Some bovine hides produce poor quality leather, termed loose leather. The structural characteristics of hides and the intermediate processed stages that lead to loose leather are not well understood. In the present study, synchrotron-based small angle X-ray scattering (SAXS) is used to investigate collagen fibril orientation at the different stages of processing (i.e. from hide through to leather) that result in both tight and loose leathers.

Results: Tight leather of a relatively isotropic texture has a lower orientation index (OI) than loose leather of a more pronounced stratified texture; conversely, tight pickled hide and wet blue have a higher OI than loose pickled hide and wet blue. There is a greater increase in OI on processing from pickled hide to dry crust (leather) for loose material. This is largely the result of a greater increase in hide thickness prior to pickling for loose hide than tight hide, followed by a greater decrease at the dry crust stage. The collagen fibrils in loose leather and wet blue more readily orient under stress than do those in tight leather. Loose leather has a more pronounced layered structure than tight leather, although this difference is not apparent from SAXS measurements of hide prior to the dry crust stage; it develops during processing.

Conclusion: The greater swelling of the loose hide during processing disrupts the structure and leads to a more layered collagen arrangement on shrinking at the final dry crust stage. © 2016 Society of Chemical Industry.