Micro DSC and NMR MOUSE studies of collagen–vegetable tannin interaction mechanism during leather making

Abstract

In this study NMR MOUSE and micro DSC techniques were used to investigate the interaction between collagen and various vegetable tannins during leather making process with the aim of gaining a deeper understanding of different water environment in relation to tannin type. We have previously showed that relaxation times may provide useful information on collagen matrix properties. The vegetable tanned leathers were obtained by patented techniques inspired from ancient recipes at the National R&D Institute for Textile and Leather, ICPI Division, Bucharest using various vegetable extracts such as myrobalan, gambier and chestnut. Longitudinal and transversal relaxation times T1 and T2eff were measured using a PM2 portable NMR-MOUSE with 20.05 MHz frequency. Micro DSC measurements were carried out with a high-sensitivity SETARAM Micro-DSC III in the temperature range (5 to 95) °C at 0.5 K min-1 heating rate. The investigated leathers showed significant differences in the values of spin-spin (T2eff) and spin-lattice (T1) relaxation times depending on tannin type that well corelates with the variation of the calorimetric parameters (denaturation temperature and enthalpy, peak shape). These results highlight the complementarity of the information obtained by the two techniques and open new ways for both designing new leather assortments and analyses of historical and archaeological leather.

Cleaner Leather Tanning and Post-Tanning Processes Using Oxidized Alginate as Biodegradable Tanning Agent and Nano-Hydroxyapatite as Potential Flame Retardant

“…Van Stiphout claimed that the short and long components of T 2 are connected to more or less rigid collagen matrix structures, i.e., short relaxation times correspond to rigid (tightly bound) structures, while long relaxation times correspond to more loosely bonded structures [ 73 ]. Accordingly, the increase of the percentage of W B corresponding to the looser bonded structures ( Table 2 and Figure 2 ) in S-OSA3 (32%) compared to S-OSA2 (14%) and S-GA1 (12%) can be interpreted in terms of an increased chain mobility and reduction of tightly bonded structures [ 74 ]. This suggest a less densely packed collagen matrix and could be explained by the higher molecular mass distribution and lower amount of aldehyde groups of low OD OSA [ 55 ].…”

Oxidized Alginate and Nano-Hydroxyapatite as Biodegradable Tanning Agent and Non-Toxic Flame Retardant for cleaner leather tanning and post-tanning processes

“…Van Stiphout claimed that the short and long components of T 2 are connected to more or less rigid collagen matrix structures, i.e., short relaxation times correspond to rigid (tightly bound) structures, while long relaxation times correspond to more loosely bonded structures [73]. Accordingly, the increase of the percentage of W B corresponding to the looser bonded structures (Table 2 and Figure 2) in S-OSA3 (32%) compared to S-OSA2 (14%) and S-GA1 (12%) can be interpreted in terms of an increased chain mobility and reduction of tightly bonded structures [74]. This suggest a less densely packed collagen matrix and could be explained by the higher molecular mass distribution and lower amount of aldehyde groups of low OD OSA [55].…”