*1.1.2.1. Effect of UV and gamma radiation on the fabric dyed with natural dyes*

The irradiation of fabric is also another factor which affects the colour strength of the fabric. Previous studies show that UV irradiation adds value to colouration and also increases the dye uptake ability of the cotton fabrics through oxidation of surface fibers of cellulose. Gam‐ ma rays are ionizing radiations that interact with the material by colliding with the electrons in the shells of atoms. They lose their energy slowly in material being able to travel through significant distances before stopping. The free radicals formed are extremely reactive, and they will combine with the material in their vicinity. Upon irradiation the cross linking changes the crystal structure of the cellulose, which can add value in colouration process and causes photo modification of surface fibers. The irradiated modified fabrics can allow: more dye or pigment to become fixed, producing deeper shades, more rapid fixation of dyes at low temperature and increases wet ability of hydrophobic fibers to improve depth of shade in printing and dyeing. [13]

#### *1.1.2.2. Surface modification of meta-aramid films by UV/ozone irradiation*

Meta-aramid films surface was modified by UV/O3 irradiation, and surface properties have been investigated by reflectance, ATR, ESCA, and surface energy. Upon UV/O3 treatment, the surface roughness and the O1s/C1s atomic ratio obviously improved, resulting from the implantation of carbonyl and hydroxyl groups. The surface energy of the meta-aramid films increased substantially due to the significantly enhanced Lewis acid parameter, which pro‐ moted the acid-base interaction of the surfaces with increase in UV energy. Also meta-ara‐ mid films became hydrophilic as indicated by substantially decreased water contact angle.

The dyeability of aramid films to cationic dyes was significantly increased due to higher hy‐ drophilic surface and strong electrostatic attraction between the cationic dyes and anionic dyeing sites of the meta aramid. [14]

*1.1.2.3. Modification of polypropylene fibers by electron beam irradiation. i. evaluation of dyeing properties using cationic dyes*

Electron beams from 0.1 to several mega electron volts are used for high doses and high speeds in various industrial processes, with penetration up to several millimeters for poly‐

Surface modification by UV and IR lasers is useful in some specific applications. One key advantage of laser treatment is that the area to be treated can be very small and localized. Depending on the level of power chosen, ablation or chemical and physical changes can oc‐ cur. Various chemical changes occur on photon-irradiated polymer surfaces. When PTFE was irradiated with ArF laser at high fluencies, defluorination and surface oxidation occur‐ red. For polypropylene, formation of oxygen functional groups such as C-O and C=O groups was detected after UV laser irradiation in air and water, and in ozon. The treated surfaces were shown to have improved bond ability with an epoxy adhesive. The surface of poly(vinyl chloride) becomes electrically conductive after successive UV irradiation in chlor‐ ine and nitrogen and argon laser irradiation in air. These types of surface modification are very useful for increasing the dyeability of polymeric textile fabrics. [2] Some of irradiation

The irradiation of fabric is also another factor which affects the colour strength of the fabric. Previous studies show that UV irradiation adds value to colouration and also increases the dye uptake ability of the cotton fabrics through oxidation of surface fibers of cellulose. Gam‐ ma rays are ionizing radiations that interact with the material by colliding with the electrons in the shells of atoms. They lose their energy slowly in material being able to travel through significant distances before stopping. The free radicals formed are extremely reactive, and they will combine with the material in their vicinity. Upon irradiation the cross linking changes the crystal structure of the cellulose, which can add value in colouration process and causes photo modification of surface fibers. The irradiated modified fabrics can allow: more dye or pigment to become fixed, producing deeper shades, more rapid fixation of dyes at low temperature and increases wet ability of hydrophobic fibers to improve depth of

Meta-aramid films surface was modified by UV/O3 irradiation, and surface properties have been investigated by reflectance, ATR, ESCA, and surface energy. Upon UV/O3 treatment, the surface roughness and the O1s/C1s atomic ratio obviously improved, resulting from the implantation of carbonyl and hydroxyl groups. The surface energy of the meta-aramid films increased substantially due to the significantly enhanced Lewis acid parameter, which pro‐ moted the acid-base interaction of the surfaces with increase in UV energy. Also meta-ara‐ mid films became hydrophilic as indicated by substantially decreased water contact angle.

The dyeability of aramid films to cationic dyes was significantly increased due to higher hy‐ drophilic surface and strong electrostatic attraction between the cationic dyes and anionic

meric materials.

40 Eco-Friendly Textile Dyeing and Finishing

dyeability modification is discussed below.

shade in printing and dyeing. [13]

dyeing sites of the meta aramid. [14]

*1.1.2.1. Effect of UV and gamma radiation on the fabric dyed with natural dyes*

*1.1.2.2. Surface modification of meta-aramid films by UV/ozone irradiation*

The dyeing properties of hydrophobic polypropylene fibers using cationic dyes were inves‐ tigated to improve dyeability by electron beam irradiation and sulfonic acid incorporation. The best dyeing result was obtained when polypropylene fibers incorporated by sulfonic acid group after electron beam irradiation were dyed with cationic dyes at alkaline condi‐ tions and 30~75 kGy irradiation ranges. In order to improve the dyeing properties of elec‐ tronic beam irradiated polypropylene, sulfonic acid group which has good reactivity was introduced on the fiber. To incorporate sulfonic acid with the electronic beam irradiated (70.5 kGy) polypropylene fiber, the fibers were added and reacted to the solution of 1,4-di‐ oxane and ClSO3H at 70 o C (Figure 2).

**Figure 2.** Introduction of sulfone groups on electron beam irradiated PP.

In order to make hydrophobic polypropylene fibers dyeable, it was shown that functional group such as carboxylate was formed on fiber substrates by electronic beam irradiation.

Concerning the pH and amount of absorbed electronic beam irradiation, the color strength increased as pH increased in alkaline conditions, and also increased as the absorbed dose increased to 30~75 kGy. As a result, it was confirmed that the pH of the dyebath and the amount and the range of the absorbed irradiation could be important variables for color strength but it seemed difficult to get deeper colors.

In the case of polypropylene fibers incorporated by sulfonic acid group to improve dyeabili‐ ty, the introduction of sulfonic acid group was confirmed by ESCA analysis and it was judged that such introduction has some advantages in color strength over only electronic beam irradiated fibers. Finally, the wash fastness of dyed fabrics using cationic dyes showed satisfactory ratings of 4~5 on both electronic beam irradiated fibers and sulfonic acid incor‐ porated fibers. [15]
