Thermal stability and degradation kinetics of vegetable-tanned collagen fiber with in-situ precipitated calcium carbonate

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

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/13/2018
Publication Date: 10/14/2018
Citation: Liu, J., Brown, E.M., Uknalis, J., Liu, C., Luo, L., Tang, K. 2018. Thermal stability and degradation kinetics of vegetable-tanned collagen fiber with in-situ precipitated calcium carbonate. Journal of American Leather Chemists Association. 113(11):358-370.

Interpretive Summary: Leather making industry generates large amounts of collagen wastes during the transformation of hides and skins into leathers. In order to convert collagen wastes into valuable products, various leather fiber reinforced/filled polymer composites have been developed for a variety of applications. When thermoplastics are used as polymer matrices, processing temperatures are always higher than their melting temperatures. Thus, it is very important to have knowledge about the thermal behaviors before any attempts are made to enhance the thermal resistance of leather fibers, because collagen often undergoes thermal decomposition on heating, with deterioration of their physical properties as a result. In addition, to improve the thermal stability of collagen fiber by rational modification one should preferably have in-depth understanding of the thermal decomposition kinetics and mechanism. The present work covers the effect of in-situ precipitated calcium carbonate on thermal behaviors, thermal decomposition kinetics, as well as the decomposition mechanism of vegetable-tanned collagen fiber. Observations show that both the thermal stability and decomposition kinetics are greatly influenced by the incorporation of calcium carbonate. We anticipate that the present study will provide useful information for fabricating high-performance polymer composites based on leather fibers.

Technical Abstract: The effects of in-situ precipitated calcium carbonate (CaCO3) on the thermal stability and decomposition kinetics of vegetable-tanned collagen fiber (VCF) are evaluated by thermogravimetry. The kinetic and mechanism analysis of the decomposition stage use an integrated procedure involving model-free methods and master-plots method. Various methods are employed to calculate the activation energy of the fibers. It is shown that VCF/CaCO3 exhibits better thermal stability than VCF in the range 22-350 °C. However, thermogravimetric results also show that the presence of CaCO3 accelerates the decomposition process at higher temperatures. When the conversion values are below 0.4, the most probable decomposition mechanism for VCF and VCF/CaCO3 is random nucleation and nuclei growth (Avrami, equation A2). Above 0.4, the decomposition mechanisms of VCF and VCF/CaCO3 are most probably random degradation of nuclei as described by third (F3) and second (F2) order models, respectively. Morphological/elemental analysis showed calcium dispersed evenly over the VCF/CaCO3.