The effect of alum addition on shrinkage temperature, chemical properties, and morphology in the manufacture of vegetable-tanned leather

Abstract

Vegetable-tanned leather has several disadvantages, which one of them is low thermal stability due to insufficient cross-linking with the collagen. The addition of aluminum sulfate in the vegetable tanning process will strengthen the cross-linking between the polyphenol and collagen, as well as forms the matrix in collagen. Thus, it will improve the thermal stability. The research aimed to figure out the addition of mimosa and aluminum sulfate on the shrinkage temperature, chemical properties, and morphology of leather. The research was conducted by using a variation of mimosa concentration (15%, 20%, 25% w/w) and aluminium sulfate concentration (3%, 6%, 9% w/w). The results showed that the treatment influenced the chemical properties and shrinkage temperature. The optimum treatment was the addition of 9% (w/w) aluminium sulfate to 25% mimosa which resulted to shrinkage temperature of 99,33° (rise 18,34%); nitrogen content (8,00 ± 0,0141)%; raw skins substance content (44,46 ± 0,0778)%; tannin bound content (28,29 ± 0,0424)% and the degree of tannage (62,93 ± 0,0141)%. Based on the SEM image, the addition of aluminum sulfate after mimosa has made the collagen fiber structure to be dense, which indicates the improvement of the cross-linking between the polyphenol and collagen.

Application of Indigenous Plant-Based Vegetable Tanning Agent Extracted from Xylocarpus granatum in Semi-Chrome and Chrome Retanned Leather Production

“…The size of polyphenol molecules and the number of -OH groups determine the rise in shrinkage temperature. The kinetic stability of linkages between the tanning agent molecules and the protein's side-chain determines the shrinkage temperature [29]. In semi-chrome leather, pre-tanning with developed tannin and the addition of chromium to the re-tanning process could increase the cross-linking between polyphenol and collagen, resulting in a stable complex matrix where chromium acts as a ligand [29].…”

“…The kinetic stability of linkages between the tanning agent molecules and the protein's side-chain determines the shrinkage temperature [29]. In semi-chrome leather, pre-tanning with developed tannin and the addition of chromium to the re-tanning process could increase the cross-linking between polyphenol and collagen, resulting in a stable complex matrix where chromium acts as a ligand [29]. As a result, the hydrothermal stability of the tanned leather showed an elevated level.…”

Chrome-Free Tanning: Effect of a Combination Tannage Based on Mimosa and Biogenic Silica from Rice Husk

“…The principle in the vegetable tanning process is quickly penetrating the tanning agent into the skin collagen with a small molecular size and small binding power [28]. The weakness of vegetable tanning is the stability of the leather to low heat stability and producing stiff, dense, and hard leather [29]. To increase the stability of the leather to heat, the soft and smooth leather can use combination tanning using silica [30,31].…”