Submitted to: American Chemical Society National Meeting
Publication Type: Proceedings
Publication Acceptance Date: May 1, 2009
Publication Date: July 20, 2009
Citation: Liu, C., Latona, N.P. 2009. Effects of Milling on the Fibrous Structure and Mechanical Behaviors of a Collagen Material--Leather. In: Proceedings of the American Chemical Society National Meeting, Division of Polymeric Materials: Science and Engineering, August 15-20, 2009, Washington, D.C. PMSE Preprints. 101:775-776. Technical Abstract: Leather, a fibrous collagen material, is a high value coproduct of the meat industry. Milling is being practiced in the tannery to mechanically tumble and therefore soften leather for adequate stiffness and feel. However, there is no report regarding its effects on the structure change and physical properties of leather. This investigation is aimed to address these concerns by the leather industry. Our studies showed milling caused a significant decrease in the stiffness, but brought very little change in mechanical strength and toughness. Electron scanning microscopic observation showed that the milled leather has an opened fiber structure; the fibers are well separated from each other, whereas the non-milled samples show the fibers are stuck together. The opened fiber structure is the key for gaining softness. Moreover, leather products in service are constantly being stretched. To understand the mechanical behavior of leather products under cyclic stretching, we measured the energy loss (hysteresis) during the cyclic tensile tests using an advanced computing program. Data showed that hysteresis is the greatest for the first cycle; thereafter, the rest of hysteresis values are relatively unchanged. We also discovered that milling significantly decreases the hysteresis. This implies a structural change occurs during milling, resulting in a removal of the residual stress that was introduced during the leather making process.