Abstract

Mechanical tensile and tear tests are used for qualitatively evaluating leather. The tests express the physical response of the tanned collagen fibre bundles subjected to stretching. Unlike mammals, the collagen fibre bundles in fishskins form overlapping layers, oblique to each other. This arrangement can influence the mechanical behaviour of the material and, therefore, must be taken into account when establishing the specimenʼs directions. Despite this peculiarity and due to the absence of specific technical norms for the position and preparation of specimens for testing, qualitative research with fish leather has used parameters established for mammals. Thus, this study aimed to verify the influence of the collagen fibre bundle arrangement as observed by scanning electron microscopy (SEM), on the qualitative aspects of Nile Tilapia (Oreochromis niloticus) leather. The skins were tanned with chrome, associated with oxazolidine. Tilapia leathers were analysed for their physical-mechanical properties, adopting cut directions of parallel, perpendicular, dorsal-ventral and ventral-dorsal, all with reference to the Tilapia cephalocaudal axis. Skin and leather evaluation through scanning electronic microscopy (SEM) revealed layers with continuous fibres bundles interspersed by layers of continuous fibres arranged in an oblique direction. The data revealed no statistical difference for the side (right and left) from which the specimens were taken. However, different behaviours of tensile strength, percentage elongation, and tear strength were observed. The tensile strength of the orange-brown leather was higher for the perpendicular direction and lower for cutting in the parallel direction. Regarding stretching, the parallel cut presented the highest value, lower for the dorsal-ventral and ventral-dorsal cuts. As for tear strength, higher values, were observed for the perpendicular and ventral-dorsal cuts. Results showed the influence of skin organisation on leather resistance and the need for method standardisation, elaborating specific norms for the qualitative evaluation of fish leather.