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Title: Mechanical properties and area retention of leather dried with biaxial stretching under vacuum

Author
item Liu, Cheng Kung
item Latona, Nicholas - Nick
item Ramos, Mila
item Goldberg, Neil

Submitted to: Journal of Materials Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2009
Publication Date: 4/1/2010
Citation: Liu, C., Latona, N.P., Ramos, M., Goldberg, N.M. 2010. Mechanical properties and area retention of leather dried with biaxial stretching under vacuum. Journal of Materials Science. 45(7):1889-1896.

Interpretive Summary: There is an increasing pressure for the leather and hides industry to produce leather without using chrome salts, i.e. chrome-free leather. In recent years, chrome-free leather has gradually gained commercial importance, particularly for automobile upholstery applications and children’s footwear. This research is to investigate an improved drying method, merging stretching and vacuum drying together. This is because vacuum drying offers fast speed and low temperature drying, which is particularly advantageous to heat-vulnerable chrome-free leathers; because they often have a lower shrinkage temperature. On the other hand, adding stretching during vacuum drying can potentially increase the area yield. We have established optimal drying conditions to achieve a significant increase in area yield with good leather quality. The leather and hides industry may use this research result to improve the quality of chrome-free leather, increase area yield and therefore better profits.

Technical Abstract: The conversion of animal hides to leather involves many complicated chemical and mechanical operations. Drying is one of the mechanical operations, and plays a key role in determining the physical properties of leather. It is where leather acquires its final texture, consistency and flexibility. We have investigated a drying method using a combination of vacuum and biaxial stretching. Total area loss often accompanies drying of leather; however, by adding a stretching action during vacuum drying one may significantly increase the area retention and dimensional stability. Moreover, this method is particularly advantageous to heat-vulnerable organic tanned leathers because vacuum drying offers fast moisture removal at a low temperature. We investigated this dual functional drying method and observed how drying variables affected the mechanical properties and area retention of chrome-free leather. We used a Central Composite experimental design to formulate the relationship between drying variables and resultant leather properties into second order polynomial equations. Results showed that the stretching applied in a drying operation significantly affects mechanical properties, area retention and thickness of leather. Moreover, studies showed that biaxial stretching increased the tensile strength but had less effect on fracture energy. A significant area increase with good properties can be achieved under an optimal drying condition.