Tensile and viscoelastic characterization of Kenyan indigenous Boran cow hide dermis

Abstract

The wide range of applications, the industrial processing techniques and storage of collagenous materials expose them to a variety of environmental conditions such as temperature, humidity and solar ultraviolet (UV) radiations. In this study, a freshly flayed hide from a mature Boran bovine was prepared to pickling stage using conventional tanning processes. The hide was then cut into two halves along the backbone. One half was left at pickled stage while the other half was tanned using Chromium Sulphate. Suitably cut specimens from each pelt in parallel and perpendicular to the backline were then taken to determine their tensile properties using Instron Testing Machine, Model 1101. Effect of direction of sampling, pickling and chrome tanning on the tensile properties was determined. Other suitable samples were exposed to solar radiation for a duration of 0-24 hours and artificial Ultraviolet radiation for 0-30 hours to determine their effects on viscoelastic properties. The samples were conditioned in a standard atmosphere prior to Dynamic Mechanical Analysis. Effects of oscillation frequency and temperature were also determined. Results showed that chrome-tanning significantly increased tensile strength (p=0.0344), storage modulus (p=0.0344), storage modulus (E’) complex and dynamic viscosity (η), shear stress (σ) and thermal stability at all frequencies and temperatures. However, it decreased the percentage elongation, loss modulus, tan δ, and shear strain. Hence tanning makes molecular chains difficult to slide over each other when shearing forces are applied. Hence, tanning stabilizes leather structure. Bovine hide showed dispersion phenomenon with frequency of 30 Hz probably its natural frequency. Solar radiation decreased storage modulus but as the duration of irradiation increased, the modulus started to increase gradually. Both tan δ and thermal stability decreased progressively with both solar and artificial radiations. Hence sun-drying during tanning can be discouraged especially for strong and stiff leather. Tensile properties showed that Boran bovine hide meets the international UN standards for leather. The study recommends rearing of Boran bovine breed.