Analysis of the Thermal Migration Issue in Disperse Dyes

Thermal migration is a phenomenon where disperse dye migrates upon heating during high-temperature treatment of polyester after dyeing.

So, what are the causes of thermal migration? 

How can it be prevented?

I. Impact of thermal migration on disperse dyes:

1. The color light of the dyed material changes;

2. Decreased friction durability;

3. Decreased wash and perspiration fastness;

4. Decreased lightfastness;

5. Drying fastness decline;

6. Causing staining or color transfer to other fabrics during ironing.

II. Causes of Disperse Dye Thermal Migration:

Thermal migration is a redistribution phenomenon of disperse dyes in a two-phase solvent system (fiber and auxiliaries), where dyes are dissolved by auxiliaries retained in the outer layer of the fiber under high temperature or prolonged storage conditions, and then transported to the fiber surface.

Fiber residue auxiliaries generally originate from:

1. Lubricants, antistatic agents, etc., added during spinning or weaving;

For reference: What types of oils need to be removed during polyester pretreatment?

2. Various auxiliaries added during dyeing and finishing processes, such as refining agents and softeners; residual nonionic surfactants are more prone to causing dye migration under heat;

PS：

1. There is no absolute correlation between the sublimation resistance of disperse dyes and thermal migration;

2. Disperse dyes with different structures exhibit varying thermal migration under the same conditions.

3. Prevention of Thermal Migration of Disperse Dyes:

1. All oils (auxiliaries) added during the spinning or weaving process must be thoroughly removed;

2. During the formulation of the process flow, the auxiliary agents used in pretreatment and dyeing should be rinsed off as thoroughly as possible;

3. When selecting post-treatment additives, thermal migration tests must be conducted.

IV. Detection of Fabric Thermal Migration Phenomenon:

Using dimethylformamide (DMF) as the solvent, the dyed fabric was immersed at room temperature for 3 minutes. The dye that migrated to the fiber surface would detach into the DMF, and the amount of dye detached could indicate the degree of thermal migration of disperse dyes in the fabric.