Proposal and application of a new method to determine leather shrinkage temperature

Leather is a natural material made of collagen fibers that have been stabilized through a tanning process. One of the leather’s characteristics is that if it is gradually heated in an aqueous solution, it reaches a temperature at which the fibers deteriorate and a sudden and irreversible shrinkage occurs. This shrinkage is a consequence of the rupture of collagen fibers bonds. Depending on the level and quality of the tanning process it happens at different temperatures. The value of this temperature is an indicator of the degree of tanning of the leather. A higher value indicates more durable leather and higher quality.The most widely used method to determine leather shrinkage temperature is the standardized method ISO 3380:2016. This method measures the temperature of leather contraction using a device that involves an operator attention throughout the test. This makes it an inaccurate and subjective method.There are currently other methods to determine the temperature of shrinkage, mainly: scanning calorimetry, microscopic hot table, differential thermal analysis and thermomechanical analysis. All of them need expensive equipment and specialized personnel. The cost of using these methods as well as the accuracy required for practical purposes in the day-to-day operation of the tanning industry make it unfeasible to use them.This work presents a new method to obtain the shrinkage temperature by measuring the force that the leather exerts when it contracts. The results obtained in the different leather samples are similar to those obtained with the ISO method, furthermore with smaller error and lower dispersion values. The material used has a low cost and it is commonly used in any industry, which makes highly feasible the implementation of the proposed method to perform quick tests by the production line.