Influence of UV radiation on the viscoelastic properties and dynamic viscosity of bovine hide using dynamic mechanical analysis

Abstract

The wide range of applications of collagen-based materials has triggered research interest especially on the effect of environmental factors in that these materials are exposed to during processing and application. As the applications of these collagenous materials continue to increase such as in the field of medicine, more studies are required to gain more insight into their properties. Collagen is a natural biopolymer whose structure is sensitive to ultraviolet (UV) radiations, which alters its mechanical properties. In this study, the influence of artificial UV irradiations, wavelength 254 nm, on the viscoelastic properties and dynamic viscosity of both pickled and tanned hide was investigated by dynamic mechanical analysis. The influence of tanning on the viscoelastic properties and dynamic viscosity was also investigated. Freshly flayed bovine hide was conventionally prepared to pickling stage and split into two identical halves along the backline. One half was tanned using chromium sulfate, while the other half was left at the pickled stage. Samples of appropriate dimensions from both the pickled and tanned hides were cut and irradiated with artificial UV light for different time duration of 6–30 h. The irradiated samples were then analyzed using the DMA in the multi-frequency mode. It was found that irradiation caused an increase in the storage modulus (E′) of pickled hide over the entire irradiation of 6 h followed by consistent decrease up to a duration of 30 h. Tanning caused an increase in tanδ that consistently decreased with the increase in the duration of irradiation. In addition, UV irradiation caused an increase in dynamic viscosity of pickled hide, but a decrease in tanned hide. The results show the predominant elastic nature of bovine hides as indicated by tanδ magnitudes less than a unit.