Submitted to: International Union of Leather Technologists and Chemists Societies
Publication Type: Proceedings
Publication Acceptance Date: 6/15/2011
Publication Date: N/A
Technical Abstract: In prior research from this laboratory, the successful use of glutaraldehyde-modified gelatin as a filling agent was described, but because of environmental concerns, we considered looking into other more environmentally benign crosslinking agents. We examined whether the extensively reported enzymatic polymerization of gelatin using microbial transglutaminase would effectively produce filler products. Research was directed toward optimizing desirable functional properties (e.g., gel strength and thermal stability), to produce materials as components of filling or finishing agents in leather manufacturing or for other industrial applications. Additionally, biopolymers, formed by enzymatic crosslinking of dissimilar proteins, have the potential for generating novel products and were also prepared. We enzymatically reacted gelatin with casein or whey proteins and found that unique, highly polymerized products were obtained. These modified products, both gelatin alone and biopolymers, were applied to enzymatically-treated blue stock, and using fluorescent labels, we found that fillers were bound to the leather and were not removed during further processing. We applied the biopolymer treatments to lower quality hides such as those exhibiting “Spring Break”. Prior to treatment, when these hides were examined using SEM and X-ray microtomography (Micro-CT), the fiber structure in the “Spring Break” hides was considerably different than the normal hides, with the former showing a tighter, cement-like structure. Subsequently, when these hides were treated with biopolymers, retanned, colored and fatliquored (RCF), and mechanical properties determined, almost no significant differences in the mechanical properties were found between the treated and control samples. With respect to subjective evaluations, all parameters of the treated hides were superior to the untreated control samples. Stereo microscopic images of the treated belly areas showed a dramatic enhancement in grain surface characteristics. When biopolymer products were applied to non chrome-tanned hides (wet white), it was found that subjective evaluation of treated hides showed for the most part, fullness, color, and overall evaluation improved, but perhaps a more robust filler could be employed to facilitate a better break. As seen in previous studies, the mechanical properties of the treated wet white leather were not significantly different (other than in thickness) from controls. SEM images of the wet white have suggested a difference in fiber structure between controls and treated samples, with the latter having a more open structure. Applying these treatments to low quality “Spring Break” hides or chrome-free hides makes economic sense. Leathers are produced that have increased cutting area, and these renewable resources have the potential to replace petroleum feedstuffs that are increasingly becoming scarce as well as expensive.