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Abstract:
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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.
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