Sublimation is the process of phase change from solid to gas , without going into liquid phase.
Fastness to sublimation is probably the most important requirement of dyed polyester, apart from fastness to light. The migration behavior and wet fastness of disperse dyes on polyester are closely involved with their response to heat treatments.
Adequate fastness to heat is essential so that the dyed material will withstand the conditions encountered in
1. Heat setting,
2. Durable pleating
3. Ironing or pressing of the goods during the making-up of garments.
4. Finishing processes where high temperature is involved.
5. Thermal fixation of prints.
The poor sublimation fastness results into following problems
1.Change in original shade
2.Staining on adjacent fibers in contrast dyed fabrics.
3.Poor color yield and fixation rate in thermal fixation of prints.
4.Staining of dyed polyester sewing threads after stitching and embroidery in contrast stitched and embroidered articles.
5.Cross staining during storage.
How to avoid the problem due to poor sublimation fastness
Since the problem of poor sublimation is concerned to polarity of substation groups in dye molecule , therefore following steps are suggested to avoid the problem,
1.Pre heat setting most of the fabrics before dyeing.
2.Carefully selecting the dyes so that all component yarns have satisfactory fastness in multicolored/contrast color designs ,where fabric is post heat set.
3.Selecting high sublimation dyes for dark shades , and medium /low sublimation dyes for pale shades.
4.The sublimation fastness influenced by the dyeing conditions and dyeing cycle followed, therefore the dyeing cycles must be optimized for best sublimation fastness.
How to test the sublimation fastness of disperse dyes
The sublimation fastness of disperse dyes is usually tested for staining and shade change , tested at 180 oC /210 oC for 30 seconds and rating is done on 1-5 grey scales.
Standard Test Method for Sublimation fastness testing.
AATCC Test Method 117-2004