Abstract:
Using mimosa tannin as vegetable tanning agent and oxazolidine as aldehydic tanning agent,the effects of hydrogen bond,hydrophobic bond and side amino group of collagen on vegetable tanning,aldehyde tanning and vegetable-aldehyde combination tanning were investigated.Results indicated that aldehyde predominantly reacted with the side amino group of collagen even it was used after vegetable tanning.However,aldehyde could further react with vegetable tannin to form cross-linkage between collagen and vegetable tannin if highly nucleophilic sites in tannin molecules were available.As a result,the synergistic effect of the combination tanning in increasing hydrothermal stability of collagen fibers was achieved and the association between vegetable tannin and collagen was remarkably stabilized.This mechanism is appropriate for describing combination tanning with condensed tannins that contain nucleophilic sites.For hydrolysable tannins,however,no aldehydic cross-linkage between collagen and tannin could be observed.In (general),this research revealed the fact that the actual features of vegetable-aldehyde combination tanning should be different from the previously assumed one.With the mechanism suggested in this paper,all the phenomena in (vegetable) tannin-aldehyde-collagen interaction could be well understood.