Characterization and thermal properties of polygenipin-crosslinked hide powders

Authors: LIU, JIE - Zhengzhou University; Liu, Cheng Kung; Brown, Eleanor - Ellie; KEYONG, TANG - Zhengzhou University

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2018
Publication Date: 4/1/2018
Citation: Liu, J., Liu, C., Brown, E.M., Keyong, T. 2018. Characterization and thermal properties of polygenipin-crosslinked hide powders. Journal of American Leather Chemists Association. 113(4):96-104.

Interpretive Summary: The development of high quality chrome-free leather and the utilization of proteinaceous byproducts of tanning have long been challenges for the leather industry. ARS scientists in Wyndmoor, Pennsylvania have developed the technology to produce green composites from solid fibrous collagen wastes generated in tannery. Recently they have demonstrated that genipin, a non-toxic and naturally occurring crosslinker, can add stability to these composites. Genipin is known to polymerize, forming polygenipin, under mildly alkaline conditions. The results of current research demonstrate that polygenipin can crosslink collagen, in powdered hide, and that by varying the polymerizing conditions, both the thermal stability of the crosslinked product can be varied. In addition, different degrees of genipin polymerization imparted blue or brown colors to the crosslinked product without the need for dyes. Thus, polygenipin crosslinked collagen may potentially have a role in the development of chrome-free tannages as well as biomedical and packaging applications.

Technical Abstract: Genipin is a naturally occurring iridoid compound, it is widely used as an ideal biological protein crosslinking agent due to its low toxicity compared to glutaraldehyde and formaldehyde. Under alkaline condition, genipin could undergo ring-opening polymerization via nucleophilic attack of hydroxyl ions followed by an aldol condensation. Because of the fact that polygenipin could create long-range intermolecular crosslinking between protein chains, preliminary investigations have been carried out to study effect of polygenipin crosslinking on color and thermal stability of hide powder by using colorimetry, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results show that the peak denaturation temperature (Tp) for hide powders obtained from DSC increased to a maximum and then decreased with increasing of the molecular weight of polygenipin. Degree of crosslinking was evaluated and the results suggest that thermal stability of hide powder is influenced not only by degree of crosslinking, but also by the type of crosslinking. Thermogravimetric analysis also confirms that long-range intermolecular crosslink bridges formed between collagen molecules results in more thermally stable hide powders. This study suggests that polygenipin can be potentially useful in producing eco-friendly leather.