The glass transition temperature of leather and its implications to the leather industry

摘要

Leather shows both flow-like behaviour as found in a liquid, and elastic spring-like behaviour as found in a solid, and can be described as a non-linear viscoelastic material. Because of this behaviour, mechanical energy applied to a piece of leather will partially dissipate through liquid-like deformation, and be partially stored within the elastically deforming molecules. When the applied energy is released, the stored energy will be used to recover part of the original shape. Changes in viscoelastic properties with respect to time or temperature can be studied by a thermo-mechanical technique called Dynamic Mechanical Thermal Analysis (DMTA). For a non-crystalline polymer, as the temperature increases from cold additional chain movements can occur at specific temperatures, which is called a relaxation process. These are said to be softening/viscoelastic transitions. The major softening transition of an amorphous polymer is known as the glass transition (Tg). Sometimes the Tg can be viewed as the onset of greater molecular flexibility, giving liquid-like behaviour to the solid. Eventually, such liquid-like behaviour is constrained only by cross-links between the long molecular chains. However, the major thermal softening transition of a structured/crystalline polymer is melting. Due to the semi-crystalline nature, leather displays transitions that are characteristics of both materials.