Madhan, B. (PhD)Getaneh, Andualem2020-12-242023-11-282020-12-242023-11-282014-09http://etd.aau.edu.et/handle/12345678/24324Chrome is the well-established tanning system adopted globally. Consumer awareness and short coming of chrome tanning system calls for a need for the development of chrome free tanning, Hence this research work is focused on, the development of silica and vegetable tanning agent (Tara) combination tanning system as an alternative to chrome tanning. This tanning system eliminates the use of chromium in tanning process thereby environmental impact of chromium can be avoided. Silica remains in solution at a narrow pH range and hence in order to keep the silica in sol at pH of about 3, silica tanning salt was prepared by masking with salts viz., sodium citrate and sodium tartrate. The combination tanning based on silica and tara were optimised for the amount of tara, order of addition and masking salt used for the preparation of silica tanning agent. The order of addition of silica and tara, amount of tara and also the type of masking agent had a significant influence on the shrinkage temperature, physical strength and organoleptic properties of the leathers produced. Tanning system with tara followed masked silica gives resulted in wet white leathers with shrinkage temperature of 80oc. Among the combination system evaluated, leathers obtained by vegetable (Tara) pretannage followed by retannage with masked sodium metasilicate were observed to be stronger, fuller and better general appearance with the durable characteristics. In contrast, pre-tanning with masked sodium metasilicate resulted in leathers with poor organoleptic properties and less hydrothermal stability. In general the characteristics of the leathers obtained by tara- silica combination system provides leathers with good organoleptic properties and comparable physical strength for upper leathers. Physical testing and organoleptic properties of the matched pair leathers of the tara-silica combination tanning system were comparable to that of chrome tanned control leathers. Skins stabilized with tara - silica combination tanning could be adapted to shaving readily; most important is that it would not produce wastes containing chromium means it is zero chrome discharge because chromium is not used in this tanning system. Therefore the tara-silica combination tanning is a good tanning system for the manufacture of upper leathers. The tara-silica combination tanning system also resulted in leathers with good buffeability and hence the leather made from this tanning system is also suitable for the manufacture of suede leathers especially for upper. The cost of the new system is higher but can be compensated with the environmental benefits by eliminating chrome in leather manufacture.en-USTanningSodium MetasilicateTaraChrome Free TanningThesis