Fastness of chrome tanned leather and chrome free leather

Importance of chrome free leather or vegetable tanned leather
Although chrome tanned leather because of its excellent heat and light fastness properties are being replaced by other means of tanning such vegetable or synthetic tanning agents.
Chrome-free leather has gradually gained commercial importance, particularly for automobile upholstery applications. In many respects, however, chrome-free leather is inferior to chrome-tanned leather. UV and heat are known to be more detrimental to chrome-free leather than to chrome-tanned leather, especially in regard to the colorfastness of dyestuff and mechanical properties. Temperature, UV radiation, and humidity are key environmental factors that affect leather properties. The role of humidity and its interaction with UV radiation and temperature on leather properties, however, are not clear to the leather industry, and this information is needed for formulation of antioxidants that will protect chrome-free leather from UV and heat damage. Therefore, a systematic study was performed to formulate the relationship between these three environmental variables and resultant colorfastness and mechanical properties. A second order regression equation was derived to plot response surfaces that clearly illustrate the relationship between the environmental variables and colorfastness, as well as the resultant physical properties. Observations showed an intriguing interaction between humidity and radiation dosage. Measurements revealed that an increase in humidity resulted in a decrease in colorfastness and mechanical strength. However, after the UV radiation dosage reaches a certain level, an increase in humidity may actually help maintain both properties. Observation showed the stiffness decreased steadily with humidity, whereas the toughness index slightly increased with humidity. This study also used differential scanning calorimetry (DSC) to determine the denaturation temperature as a function of various environmental conditions. We observed a correlation between colorfastness and the denaturation temperature.