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United States Department of Agriculture

Agricultural Research Service

Research Project: NEW AND EFFICIENT PROCESSES FOR MAKING QUALITY LEATHER
2010 Annual Report


1a.Objectives (from AD-416)
Develop new technology for preparing hides for tanning. Establish drying and finishing processes and develop in-line nondestructive tests for improving the quality and durability of leather. Hide Preparation: The additional funding will be used to expand the scope of hide preparation research by investigating ways to impart efficiencies to short-term hide preservation (brine-curing).


1b.Approach (from AD-416)
Oxidative chemicals will be evaluated for dehairing activity. Following dehairing, fleshing and splitting, the grain split will be further dehaired if necessary to remove remaining hair stubble. Further processing would complete the conversion of hide to crust leather. Enzymes (keratinases, dispase, acidic or alkaline proteases, and type IV collagenases will be evaluated as alternatives to chemical dehairing. Processes will be developed for partial or total removal, from limed hides, of proteoglycans (such as decorin) and glycans (such as dermatan sulfate) by first 'opening-up' the hides thoroughly to the entrance of chemicals and then treating the hides in the presence of concentrated salts with chymotrypsin, trypsin, pancreatic bate, halophile protease and/or glycanases (during bating). Both the decorin coreprotein and the sulfated glycan content will be measured before and after application of the novel treatment, and mechanical and physical changes in the resultant leather will be evaluated. The effect of treatments on the physical and mechanical properties of leather ultimately made from the treated hides will be assessed. A mathematical, predictive drying model for chrome-free leather will be established and compared to the earlier one developed for chrome-tanned leather. Based on the new model, the optimal drying conditions for chrome-free leather will be identified. A finishing process will be developed that will improve the UV- and heat resistance of automobile upholstery leather. Alpha-tocopherol (Vitamin E) will be added during wet processing or added to the finishes and applied to the grain layer of the leather during the finishing process. In-line nondestructive testing technology by acoustic emission (AE) will be developed to assess the mechanical properties of leather following drying, staking, buffing, drum milling, and finishing. The additional funding will be used to evaluate processes for expediting the diffusion of salt into the hide. The ability of acoustic/mechanical energy or alternative salt formulations to shorten the time of brining and possibly decrease the salt requirement will be assessed.


3.Progress Report
The original project 1935-41440-013-00D expired on June 24, 2009. There was a bridge project 1935-41440-016-00D that continued the research efforts until June 14, 2010. Under project 1935-41440-013-00D (June 2004 to June 2009), we developed new technology for preparing hides for tanning, established drying and finishing processes, and developed nondestructive tests for improving the quality and durability of leather. This past year, our research mainly aimed to enhance the effectiveness of our previously developed technology under project 1935-41440-013-00D. In an extended CRADA, we collaborated with industry to optimize the dehairing process using relative mild oxidative chemicals, which had showed great potential to replace the commonly used and toxic sulfide dehairing process. Moreover, our research showed additional removal of decorin could be achieved when specific proteolytic enzymes were added during the pretanning stage of tanning hides into leather. More pronounced improvement in leather quality was observed in oxidatively dehaired hides than those dehaired traditionally with sodium sulfide. Our results showed that in general, the lower the residual decorin content the better the quality of leather. As the decorin content decreased, the leather product became softer, more stretchable than, and as tough as the control leather tanned without co-treatment with proteolytic enzymes. In 2010, we also developed an AE method that captured acoustic signals from both the grain and corium sides simultaneously, thereby giving a more accurate assessment of the leather quality. The method can measure the quality of leather without wasting the leather as in traditional destructive testing.


4.Accomplishments
1. Developed a novel system for removing decorin to improve the quality of leather: ARS researchers at Wyndmoor, PA have developed ways to improve the quality of leather by further removal of a glue-like minor component--decorin, which is a proteoglycan (part protein and part carbohydrate). Significant removal of decorin was observed when specific proteolytic enzymes were added during the pretanning stage of converting hides into leather. More pronounced improvement in leather quality was observed in oxidatively dehaired hides than those dehaired traditionally with sodium sulfide. Our results showed that as the decorin content decreased, the leather product became softer, more stretchable, and as tough as and sometimes even tougher than the control leather tanned without co-treatment with proteolytic enzymes. This research has provided a new technology to significantly improve the quality of leather.

2. Vitamin E improves the UV and heat resistance of leather: Ultraviolet light (UV) and heat can have a detrimental effect on the color and mechanical properties of leather. This research aims to develop a process treatment that is environmentally friendly and yet significantly increases the UV and heat resistance of leather. ARS researchers at Wyndmoor, PA added alpha-tocopherol (Vitamin E), a natural antioxidant, to the coatings of leather that had been tanned with an organic tannage without using chromium salts. Observation showed that leather treated with alpha-tocopherol resulted in significant improvement in strength retention and color fading resistance against UV radiation and heat. The results of this research could lead to an increase in demand for domestic production of high quality, durable leather, thereby contributing to the viability of the domestic tanning industry.

3. New nondestructive methods to test Leather quality: ARS researchers at Wyndmoor, PA have developed a nondestructive acoustic emission (AE) testing method to replace the traditional destructive testing methods for leather, thereby reducing the waste in the tanneries. This novel testing method measures ultrasonic sound waves emitted by the leather when it is slightly deformed. Researchers developed AE methods using dual sensors that capture AE signals from both the grain and corium sides simultaneously, thereby giving a more accurate assessment of the leather quality. This research has provided the industry with a nondestructive way in which to evaluate the quality of product without damaging the leather.


Review Publications
Liu, C., Liu, L.S., Latona, N.P., Ramos, M., Latona, R.J. 2010. The Use of Mixed Tocopherols to Improve UV and Heat Resistance of Leather. Journal of American Leather Chemists Association. 105(1):9-15.

Liu, C., Latona, N.P., Lee, J. 2010. Acoustic emission studies for leather using dual sensors. Journal of American Leather Chemists Association. 105(4):109-115.

Liu, C., Latona, N.P., Lee, J., Cooke, P.H. 2009. Microscopic observations of the leather looseness and its effects on mechanical properties. Journal of American Leather Chemists Association. 104(7):230-236.

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.

Ramos, M., Liu, C. 2010. A novel system of removing decorin, a minor proteoglycan of bovine hides, to improve the quality of leather. Journal of American Leather Chemists Association. 105(7):222-228.

Last Modified: 12/22/2014
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