**5. Acknowledgements**

368 Textile Dyeing

PET Nylon PET Nylon PET Nylon Dry Wet

5 (4-5)

4-5 (4-5)

4-5 (4-5)

4-5 (4-5)

3-4 (3-4)

4-5 (4-5)

4 (4)

4-5 (3)

4-5 (4-5)

> 4 (3)

3-4 (3)

4-5 (4)

Table 9. Wet fastness properties of disperse dyes on PLA before and after heat treatment

With promising properties, PLA has been intensively studied in order to gain its maximal benefit as a textile fiber for the textile industry. PLA fiber possesses many comparable properties to the conventional polyester, PET, but its thermal and alkaline sensitivities are inferior, therefore, milder processing conditions used in textile production are suggested for PLA. PLA can be dyed with disperse dyes to provide a stronger and brighter shade as compared with PET. The differences in dyeing properties of disperse dyes on PLA and PET are explained to be a result of different interactions between the polymer (fiber) and the dye molecule. The polymers (PLA and PET) are influential on the spectroscopic properties of the dyes. PLA provides less stabilization of the dye molecules in its excited states as compared with the case of PET, consequently, different shade and strength of the dyes are observed. The difference in dyeing properties of disperse dyes on PLA and PET was explained by several researchers that the key factor affecting this was the solubility parameter. The dye having a solubility parameter close to that of PLA, would exhibit high sorption on the fiber whereas those with solubility parameter being largely different from the fiber, would have low sorption. A new concept was proposed that there were other important factors, apart from solubility parameters, being influential on the dyeability of disperse dyes, for example hydrophilic/hydrophobic nature of the dye and the dye-fiber affinity. A study on color fastness of disperse dyes on PLA in comparison with PET indicates that fastness properties of the dyed PLA is slightly lower (about 0.5-1.0 unit of grey scale) than those on PET. A higher degree of thermal migration of the dye was found on PLA after subjected to heat

Alkaline perspiration\* (E04)

> 4 (3-4)

> > 4 (4)

4-5 (4-5)

4 (3-4)

3 (2-3)

> 4 (4)

Rub\* (X12)

> 4 (3-4)

> > 4-5 (4)

4 (4)

4-5 (4-5)

4-5 (4-5)

4-5 (4-5)

4-5 (4)

5 (4-5)

4-5 (4-5)

> 5 (5)

> 5 (5)

4-5 (4-5)

Acid perspiration\* (E04)

4-5 (4-5)

> 4-5 (4)

4-5 (4-5)

> 4-5 (4)

4 (3-4)

4-5 (4-5)

\* Values in parentheses are those after heat treatment for 30 s at 130oC

Dye

1

2

3

4

5

6

**4. Conclusion** 

Wash\* (C06/B2S, 50°C)

> 2-3 (2-3)

> 2 (1-2)

> 3 (2-3)

> > 4-5 (4)

> > 4-5 (4)

4 (2-3)

4 (4)

3 (3-4)

> 3-4 (3)

4 (3-4)

4 (3-4)

4 (2-3) The authors are indebted to The Thailand Research Fund and Office of the Higher Education Commission, Thailand for their support on the research (MRG5080242) contributing the main information of this chapter and thanks is given to the National Science and Technology Development Agency (NSTDA) for their support on the research of thermal migration study of disperse dyes on PLA fabric (F-31-112-11-01). A great thankfulness is given to National Innovation Agency (NIA) for their support on the research topic of "Development of textile products from poly(lactic acid) fiber" (C53-53). Also, a part of this research was funded by the Center of Advanced Studies for Agriculture and Food, Institute for Advanced Studies, Kasetsart University. Finally, a special thanks is given to DyStar, Thailand for supplying chemicals and useful information.
