School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand 4442.
J Agric Food Chem. 2011 Sep 28;59(18):9972-9. doi: 10.1021/jf202579b. Epub 2011 Sep 2.
There is a large difference in strength between ovine and bovine leather. The structure and arrangement of fibrous collagen in leather and the relationship between collagen structure and leather strength has until now been poorly understood. Synchrotron based SAXS is used to characterize the fibrous collagen structure in a series of ovine and bovine leathers and to relate it to tear strength. SAXS gives quantitative information on the amount of fibrous collagen, the orientation (direction and spread) of the collagen microfibrils, and the d-spacing of the collagen. The amount of collagen varies through the thickness of the leather from the grain to the corium, with a greater concentration of crystalline collagen measured toward the corium side. The orientation index (OI) is correlated strongly with strength in ovine leather and between ovine and bovine leathers. Stronger leather has the fibrils arranged mostly parallel to the plane of the leather surface (high OI), while weaker leather has more out-of-plane fibrils (low OI). With the measurement taken parallel to the animal's backbone, weak (19.9 N/mm) ovine leather has an OI of 0.422 (0.033), stronger (39.5 N/mm) ovine leather has an OI of 0.452 (0.033), and bovine leather with a strength of (61.5 N/mm) has an OI of 0.493 (0.016). The d-spacing profile through leather thickness also varies according to leather strength, with little variation being detected in weak ovine leather (average=64.3 (0.5) nm), but with strong ovine leather and bovine leather (which is even stronger) exhibiting a dip in d-spacing (from 64.5 nm at the edges dropping to 62 nm in the center). This work provides a clear understanding of a nanostructural characteristic of ovine and bovine leather that leads to differences in strength.
绵羊皮和牛皮革的强度差异很大。皮革中纤维状胶原蛋白的结构和排列以及胶原蛋白结构与皮革强度之间的关系迄今为止仍了解甚少。基于同步加速器的小角 X 射线散射（SAXS）用于表征一系列绵羊皮和牛皮革中的纤维状胶原蛋白结构，并将其与撕裂强度相关联。SAXS 提供了有关胶原蛋白量、胶原微纤维的取向（方向和分布）以及胶原的 d 间距的定量信息。胶原蛋白的量从粒面到真皮层在皮革厚度上发生变化，在朝向真皮层的一侧测量到更多的结晶胶原蛋白。取向指数（OI）与绵羊皮的强度以及绵羊皮和牛皮革之间具有很强的相关性。强度较高的皮革具有与皮革表面平行排列的纤维（高 OI），而强度较低的皮革具有更多的非平面纤维（低 OI）。当测量与动物的脊柱平行时，弱（19.9 N/mm）绵羊皮的 OI 为 0.422（0.033），较强（39.5 N/mm）绵羊皮的 OI 为 0.452（0.033），而强度为（61.5 N/mm）的牛皮革的 OI 为 0.493（0.016）。皮革厚度的 d 间距分布也根据皮革强度而变化，在弱绵羊皮（平均值=64.3（0.5）nm）中检测到的变化很小，但在强绵羊皮和牛皮革（甚至更强）中，d 间距出现下降（从边缘的 64.5nm 下降到中心的 62nm）。这项工作清楚地了解了导致强度差异的绵羊皮和牛皮革的纳米结构特征。
