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 collagenbased 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 0 ) 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 tand 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 tand magnitudes less than a unit.

Influence of UV aging on some rheological properties of footwear leather

“…Values obtained in this paper confirm the sensitivity of following parameters, like stress at break or elongation to the UV radiation. It corresponds to results obtained in papers [18,19].…”

A Review of Natural Plants as Sources of Substances for Cleaner Leather Tanning Technologies

“…It determines the structural resistance of leather, and beyond it the material goes from being elastic to being plastically deformed [3]. Since the strength of the leather is determined by the fibrous structure and any modification of the structure, then any bond formation that occurs in the leather matrix affects these properties [10,11]. The acceptable standard minimum of tensile strength for upper leather, lining, furniture and goods is 15, 15, 10 and 10 N/mm 2 , respectively [31].…”

“…These include the physical (mechanical), hydrothermal and chemical stability, fastness, and organoleptic (tactile or sensorial character) properties of the resulting leather [7][8][9]. These properties are easily achievable by using the chromium tanning agent which, among the tanning technologies, is the most outstanding due to its superior performance characteristics it confers to leather [10,11]. Nevertheless, chromium is a limited natural resource, which when subjected to accelerated ageing conditions, oxidizes to form toxic and carcinogenic species that have an adverse impact on the environment and human health [12].…”

Effect of Crusting Operations on the Physical Properties of Leather

“…Reference [56] termed the weakening as destabilizing the crust and reversing the crosslinking action of the chrome tanning. Reversing crosslinking action definitely reduces the tensile strength and shrinkage temperature [6,9,12]. This also explains why the fibre bundle allows the constituent fibres to straighten up and align themselves in the direction of the deforming force before the fibres actually get to be stretched and hence elongation at break, softness and pliability.…”

“…Physical properties in this case play an important role of determining the specific field of applications since they determine the required performance characteristics [1,4,5]. However, the transformational journey of bovine hide to leather involves a sequence of chemical and mechanical operations that greatly alter these properties [6]. The operations can be categorized into beam house (pretanning), tanning, post-tanning (crusting or wet-finishing) and dry-finishing operations [7].…”