**6. Laser in surface modification of polymer and fabrics**

Laser modification on material surface is one of the most studied technologies. It has been shown that various materials modified by laser irradiation often exhibit physical and chemical changes in the material's surface. In general, laser irradiation could not affect the bulk properties of a polymer due to its low penetration depth (**Figure 6**) [28, 29].

**Figure 6.** Surface structure of polyester fiber under high fluence (5 pulses at 100 mJ/cm2 ) [28].

In the research which has been done by Bahtyari, the effect of CO2 laser treatment on the dyeability of polyimide fabrics reveals that, following laser treatment, the dyeability of polyamide increased significantly. This is accompanied by a significant bursting strength loss.

A multilayer coating of uniformly dispersed NPs was obtained in the process. The pretreat‐ ment with enzymes causes better adhesion of the ZnO NPs on the surface of cotton fabrics. The NPs-coated cotton fabrics inhibited the growth of *S. aureus* and *E. coli*, respectively, by

Textile dyeing assisted by ultrasonic energy has attained a greater interest in recent years. Ultrasonic-assisted dyeing of cellulosic fibers has already proved to be a better choice among

Khatri et al. in 2016 reported ultrasonic dyeing of nanofibers. They chose cellulose nanofibers and dyed with two reactive dyes, CI reactive black 5 and CI reactive red 195. Results revealed that the ultrasonic dyeing produced higher color yield (K/S values) than the conventional dyeing. The color fastness test results depicted good dye fixation. Also they have reported that ultrasonic energy during dyeing does not affect surface morphology of nanofibers. The results conclude successful dyeing of cellulose nanofibers using ultrasonic energy with better color

Laser modification on material surface is one of the most studied technologies. It has been shown that various materials modified by laser irradiation often exhibit physical and chemical changes in the material's surface. In general, laser irradiation could not affect the bulk

67% and 100% [26]

318 Radiation Effects in Materials

conventional dyeing by many researchers.

yield and color fastness results than conventional dyeing [27].

**6. Laser in surface modification of polymer and fabrics**

properties of a polymer due to its low penetration depth (**Figure 6**) [28, 29].

**Figure 6.** Surface structure of polyester fiber under high fluence (5 pulses at 100 mJ/cm2

) [28].

It has been observed that, as the laser modification of the fabric was carried out with low intensity, the concentration of free amino groups, which are necessary during dyeing with acid and reactive dyes, increased [30].

The modification induced in PLA by the ArF excimer laser radiation has been investigated by Rytlewski et al. It was found that the surface energy change was affected by surface oxidation as well as by surface roughness. ArF laser surface treatment can be an effective way of improving PLA adhesion properties [31].

Another article focused on the development of a laser pretreatment method for glass-fibrereinforced polypropylene surfaces for industrial applications. The aim of this research is to create a surface for bonding polypropylene which adheres very poorly to most of the materials and forms to the matrix material for plastic composites [32].

On the other hand, as is known, the laser is a source of energy which can be used for irradiation of different substrates and its power and intensity can be easily controlled. By using laser, it is possible to cut a great variety of material from metal to fabric. Also it would be possible to transfer certain designs onto the surface of textile material by changing the dye molecules in the fabric and changing the color quality values by laser irradiation of fabrics at reduced intensity (**Figure 7**) [33].

**Figure 7.** Some examples of denim trousers designed by laser beam method [33].

The CO2 laser-thinning method has been applied to the PET fiber to prepare the PET nonwoven fabric without using the solvent by Suzuki et al.

The obtained nonwoven fabric was made of continues microfibers with a uniform diameter without a droplet.

The laser-thinning method has been found to be effective for producing other nonwoven fabrics such as poly(L-lactic acid) and poly(glycolic acid). The schematic of setup is shown in **Figure 8** [34].

**Figure 8.** CO2 laser-thinning apparatus used for web formation [34].

CO2 laser treatment was used as a novel method for creating antibacterial properties on glass mat by Wiener et al. in 2014. Various types of metallic salts such as CuO, ZnO, and AgNO3 were applied on surface of glass mat and irradiated with the laser light beam (100 *μ*s). Metal particles were deposited on the surface of samples. The antibacterial properties of the fabrics were connected with the presence of metal particles on their surface. Wiener et al. concluded that the change in properties induced by laser can effect an improvement in certain textile products [35].

Glass fiber mat surface modifications were carried out using CO2 laser. The geometry of the experiment is visualized in **Figure 9**. In the laser tube (1) produces IR laser beam (2). In the direction of laser beam, computer-adjusted mirror is located (3) which determined the positron of irradiated place on glass fiber mat (4). The temperature of the glass fiber mat on its irradiated side cannot be measured due to high intensity of IR laser beam. So only the temperature of back side of glass fiber mat was estimated (5) by infrared thermometer (6). Laser light treatment of glass fiber resulted in interesting properties based on the mechanical properties, such as strength, modulus, and elongation of the glass fiber mat, the permeability, morphological properties, and the thickness.

Wiener et al. in 2014 concluded that by increasing the laser intensity, the strength and modulus of the mat decrease. But in the case of laser cycling treatment, the mechanical properties are improved. We observed that laser treatment causes increase of porosity and better air perme‐ ability [36].

**Figure 9.** Schematic view of the laser treatment of glass fiber and temperature measurement [36].
