Thesis Details

Thesis Title: An Investigation of the Mechanisms Causing Tendering of 100% Cotton After Repeated Commercial Launderings
Thesis Author: Jane Hughes
Abstract: Reactive tendering refers to the degradation of 100 % cotton dyed yarns that occurs after repeated commercial laundry processes. Previous research on vat and reactive dyes has found that the problem of tendering is due to the acid hydrolysis of cellulose occurring as a result of a combination of the sour used in the commercial laundry process and the pressing of the wet fabric dry. It has been determined that this degradation only occurs on reactive dyed fabrics; vat dyed fabrics do not tender. In order to find a quick solution to the problem, laundry chemical manufacturers developed an alternative sour to leave the fabric pH closer to neutral (versus the normal sour fabric pH of 4.5 to 5.0). This "alternative" sour was tested and found to delay the degradation, but not totally prevent it. However, the actual mechanism of reactive tendering has never been identified. The purpose of this work is to identify the chemical mechanism responsible for the tendering of cellulose which occurs after repeated commercial launderings. Results of this study verified that tendering of 100% cotton fabrics is due to the acid hydrolysis of cellulose. The amount of tendering is dependent upon both the type of dye selected the pH of the commercial laundry sour. Normally used laundry sours with a pH of 4.5 to 5.0 caused tendering, and buffered sours with a pH of 6.5 did not tender. Direct dye did not tender. Therefore, it was concluded that solubilizing groups did not affect tendering. Tendering was identified, however, in reactive dyes. Specifically, monochlorotriazine reactive dyes were found to have the greatest strength losses, followed by di- vinyl sulfone and mono- vinyl sulfone in terms of greatest to least strength loss. This research also indicates that the type of salt used during dyeing did not effect the single end strength after repeated commercial launderings. However, the method of fabric drying after dyeing did have an impact on the single end strength of fabrics. Fabrics thermally dried had higher strength than those that were allowed to air dry.