Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/17/2003
Publication Date: 5/1/2004
Citation: Liu, C., Latona, N.P., Lee, J. 2004. Effects of drying methods on chrome-tanned leather. Journal of American Leather Chemists Association. 99(5):205-210. Interpretive Summary: Drying is a key step in leather manufacturing. By drying, leather can acquire its final texture, consistency and flexibility. There are many drying methods currently being used in leather manufacturing. Information regarding their effects on physical properties is lacking. We therefore carried out a comparison study to determine how the physical properties are affected using current production drying methods. This new study showed the drying method significantly affects the physical properties of leather, particularly area retention and compliance. Toggle drying (the toggling of leather onto a screen during drying) produces higher area yield, but may result in stiffer leather with a poor break (wrinkle patterns on leather=s grain side). Our research results again showed that residual water content is a key factor for softness. Vacuum drying without toggling yields better toughness and softness. We also showed that a physical quantity, "toughness index," the ratio of strength to stiffness, appears to have a direct link to the resultant area retention of leather. The information derived from this investigation will be used by leather manufacturers to select the right drying methods to meet quality demands.
Technical Abstract: The drying operation is a critical leather making step to attain the required physical properties for leather products. To make quality leather, it is imperative to understand the effects of different drying methods on the physical characteristics of leather. Results from our new investigation on leather prepared with various drying methods showed the type of drying operation significantly affects the physical properties of leather, particularly area retention and compliance. Observations indicated that toggle drying produces higher area yield, but it may result in stiffer leather. One of the important findings from this study is that there is a direct link between grain break and stiffness of leather. Data indicated that stiffer leather often results in poor break. Our research again showed that residual water content is a key factor for softness. Vacuum drying without toggling yields better toughness and softness. We also presented a dimensionless quantity, toughness index, that showed a strong correlation with the resultant area retention and stiffness of leather. Toughness index is independent of the geometry of the leather samples. Therefore, even without knowing the thickness or shape of the samples, one can still make an effective comparison of properties.