Why will the white shoes become yellow after wearing for a long time?

31 \ Aug

Beautiful white shoes are easy to get dirty after a few wears, cleaning up is laborious, after washing and drying the upper will also be yellow ...These problems are probably the most "pain" brought to us by the small white shoes. So, why do shoes turn yellow? What are the standards and testing methods for yellowing resistance testing?

The reason for yellowing is that leather and rubber products in the long-term use of the process will appear in varying degrees of an aging phenomenon, yellowing is a kind of aging indicator. Footwear materials such as polyurethane (PU) materials, thermoplastic rubber (TPR) materials without UV antioxidants and coated polymer materials such as leather are susceptible to yellowing under the radiation of sunlight. In addition, fabric as an indispensable part of the upper material, in the long-term storage, transportation and wearing process is also prone to yellowing.

Unlike the many test methods for apparel yellowing resistance, the test methods for footwear yellowing resistance in China are currently only "Test Methods for Footwear Yellowing Resistance" and "Test Methods for Synthetic Leather Yellowing Resistance Determination". The two test methods are basically the same in principle, and both provide the test method for the degree of yellowing resistance of footwear gang materials, soles and other products to approximate sunlight and ultraviolet light exposure. The Light Gun Type Yellowing Resistance Testing Machine ASTM D1148 Light Gun Type Yellowing Resistance Testing Machine (labtesting-equipment.com) is a testing machine used to simulate the environment of a shipping container exposed to sunlight to test the resistance of its contents. It conforms to ASTM D1148 standard.