Improvement of Wash Fastness of Direct and Acid Dyes Applied to Silk by Aftertreatment with Syntan, SyntanlCation, and Full Backtan Processes.

To examine the effect of different aftertreatments, on dyeing of silk fibres using acid and direct dyes the dyed samples were aftertreated using different commercial systems: such as full backtan, syntan, and syntan/cation processes. When all dyeings were subjected to 180105C06 wash test, it was found that all three aftertreatments improved wet or wash fastness. However, aftertreatment of the dyeing using backtanning system showed greatest wash fastness improvement toward wash testing. A commercial syntan improved the wash fastness and the sequential application of a cationic compound to the syntanned dyeing caused further improvement in wash fastness. The effect of syntan in reducing dye removal was increased by decreasing the applied pH, which indicats that ion-ion interactions operating between the protonated end groups in the silk fibre and anionic syntan contribute towards syntan-fibre affinity. Also the effect of syntan in reducing dye removal increased with decreasing liquor ratio. Increasing the concentration of syntan that accompanied a decrease in liquor ratio can be expected to increase the degree of syntan aggregation in solution. It can be suggested that the aggregation of the syntan will occur in solution by virtue of both polar and non-polar forces operating between the large molecular size syntan molecules which in turn can be considered to result in greater uptake of the tanning agent. However, the aftertreatment with full backtan had markedly improved the fastness to washing of the six dyes used and showed greatest wash fastness improvement.