1a. Objectives (from AD-416)
1. Develop commercially viable hide preparation and leather processing methods that are environmentally friendly while maintaining and improving the quality and/or value of hide products. 1A: Develop computational and laboratory models for predicting the effectiveness of new chrome-free tanning agents. 1B: Develop improved environmentally friendly processes for hide preparation. 2. Create commercially viable hide-quality sensing technologies that are more rapid, accurate, precise, nondestructive, and cost-effective than current systems. 3. Develop technologies that enable new products from hides such as green composites (reinforced with hide fibers), nonwoven fabric filters, and new fillers and coatings for leather. 3A: Develop green composites and fibrous materials from hides. 3B: Develop new applications for tanning waste.
1b. Approach (from AD-416)
To develop a basis for designing or selecting effective chrome-free tanning agents, the results of studies of the interactions between collagen and current or proposed tanning processes will be integrated to give the best overall evaluation. The ERRC computational molecular model of collagen will be used to predict how the secondary or tertiary structure of collagen might be affected by a proposed modification. The model can predict if the modifier will fit into the structure, and how likely is the modifier to attach to telopeptide residues or form bonds with sidechains in the end-to-end gap between triple helices. Bench scale experimental model systems using collagen at different stages of molecular complexity (soluble collagen, milled collagen or powdered hide) will be used to evaluate by physical, chemical and biochemical methods the effect of these modifications on collagen. The development of effective and eco-friendly methods for removal of manure and other organic contaminants from animal hides will build on the incorporation of glycerol or biosurfactants or combination of both. Methods to enhance hide preservation using less salt or salt-free alternatives will also be developed. Environmental and economic concerns in terms of obtaining better quality hides and higher returns are the major criteria for developing and accepting new and alternative cleansing and preserving techniques. The goal is to not completely remove all of the manure prior to processing but to achieve a state where the manure/hair adhesion can be broken by a mechanical removal process without removing the hair at the root or tearing the grain. The advanced evaluation technology for the detection of hide defects and the evaluation of hide quality will be developed by incorporating airborne ultrasonic (AU) technology. Green composites will be designed and prepared with gelatin as the matrix reinforced with collagen fiber networks. Both components will be derived from hides. In addition, new fibrous products such as filters having a nonwoven fibrous structure will be prepared from fine diameter collagen fibers (fibrils). Collagen fiber networks will be obtained from split hides that have been processed to remove the noncollagenous materials. The use of chemical and biochemical techniques for enhancing the properties of tanning byproducts will proceed concurrently with the work on tanning. To demonstrate a potential role for protein recovered from leather waste, used alone or in conjunction with other renewable agricultural resources, model systems will be developed, in which these renewable resources will be treated with known chemoenzymatic crosslinking agents to determine functional properties. Effects then will be made to establish if these products would be appropriate to be used in leather processing, for example as potential fillers, coatings and encapsulating agents. Aqueous gelatin will also be combined with fibrous protein waste products, such as chrome shavings, buffing dust, feathers, and meat & bone meal, and then the mixture will be modified with enzyme to prepare products, such as films, with unique functional properties.
3. Progress Report
For the development of models to predict the effectiveness of chrome-free tannages (Objective 1a), powdered hide from hides that had been partially processed into leather by standard tannery methods and newly developed more ecofriendly methods was prepared and characterized. Computational methods were used in the development of a fundamental understanding of tanning mechanisms. Methods were developed for the inclusion of water, an essential component of leather, in molecular dynamics simulations of vegetable tanning. This progress as well as the progress for objectives 1b, and 3 addressed NP306 Action Plan Component 2 (Fibers) Problem 2A by developing technology to decrease the environmental impact and improve the processing and sustainability of hides and leather production. In the development of improved environmentally friendly processes for hide preparation (Objective 1b), new soaking solutions containing crude glycerol, biodegradable surfactant and sodium carbonate were formulated removal of hardened manure from bovine hides. Hides soaked in these new formulations produced leather with improved mechanical properties compared to hides soaked by current methods. In the laboratory, the new soaking process is more efficient, using ~25% of the traditional volume while also inhibiting bacterial growth. For the creation of commercially viable hide-quality sensing technologies (Objective 2), the airborne ultrasonic tester for nondestructive inspection of defects in leather and hides was installed and optimal test parameters established. Hides with defects were scanned and the correlation between transmitted ultrasound amplitude distribution and the size of defects determined. This research progress addressed NP306 Action Plan Component 2 (Fibers) Problem 2A by creating hide quality sensing and quantification methods and technologies that are nondestructive and more accurate than current systems. In the development of technologies for new products (Objective 3a, collagen fiber network from hides were prepared and the effects of preparation conditions on the physical properties of fiber network were characterized. Collagen fibrous networks were prepared from un-tanned hides (hides were processed through unhairing up to bating). Observation showed the dehydration methods play a key role in determining the mechanical properties and apparent density of resultant fibrous networks, which will be used as the starting materials for new product developments, such as air filters and green composites. In the development of new applications for tanning waste (Objective 3b), a chemical modification strategy, using vegetable tannins, to form a product from the proteinaceous byproducts of leather manufacturing (gelatin) and whey protein, another waste agricultural protein was developed. Polyphenolic acids, vegetable tannins, were evaluated to modify gelatin and form highly crosslinked compounds. These products have potential use as fillers or coatings for leather processing.
Taylor, M.M., Lee, J., Bumanlag, L.P., Hernandez Balada, E., Brown, E.M. 2011. Treatments to enhance properties of chrome-free (wet white) leather. Journal of American Leather Chemists Association. 106(2):35-43.