Tanning characteristics and tanning mechanism of nano-sio2

A nano-precursor which can, in situ, produce nano-SiO2 under particular triggering conditions was introduced into leather to improve the hydrothermal stability. In order to elucidate the reaction of nano-SiO2 with protein and how it influences the properties of the protein, collagen was used as a model in detailed investigations. The result from FTIR indicated that two new chemical bondings occurred during the formation of the organic/inorganic nano-hybrid. One appears to be the reaction between nano-SiO2 formed in-situ by the hydrolysis of tetraethoxy silane and the -C=N- groups of arginine, histidine and tryptophane on the collagen backbone. In a second bonding, occurring at the same time as the condensation reaction of silanol proceeds, the pendent hydroxyl groups of collagen may partly react with Si-OH and form a strong interreaction between the organic and inorganic phases. These two chemical bonds seem to contribute to the leather's high hydrothermal stability. AFM (atomic force microscopy) was used to determine the size and scale of nano-SiO2 particles in the protein. The size distribution is approx. 50-80 nm and there appeared to be no agglutination. When the bated pelt is treated with 0.2% or 0.3 wt% nano-SiO2 (based on bated pelt weight) the shrinkage temperature is raised from 68degreesC to 86.9degreesC and 95.4degreesC respectively -nano-SiO2 is thus shown to be a viable tannage.