**4. Plasma coating of nonwovens for functional and bioactive coatings**

Plasma coating techniques have been utilized to obtain functional and bioactive coatings on nonwovens to improve surface hydrophilicity, hydrophobicity, electrical conductivity, UV and electromagnetic shielding, and antibacterial properties.

Polypropylene nonwoven fabrics are commonly used for hygienic and disposable absorbent products such as diapers, feminine care products, wound dressings, and wipes. In all these applications, nonwoven needs to be wettable by water or aqueous-based liquids [41, 42]. This is usually obtained by coating the fabric with a surfactant solution lowering surface tension of

**Figure 9.** C1s peak of untreated and oxygen plasma treated sample at 80 watt and 10 minutes, (A1) PP untreated, (A2) PP oxygen plasma treated, (B1) cotton untreated, (B2) cotton oxygen plasma treated [29]

the aqueous liquid and subsequent drying of the fabric. In such case, the surfactants are effective in rendering the fabric wettable for a limited time during the use of the product. Surface treatment of nonwoven fabrics using plasma is an alternative method to improve their wettability [41].

Behary et al. [43] activated the surface of a carded and hydroentangled PET (polyethylene terephthalate) nonwoven by an air–dielectric barrier discharge atmospheric plasma. The wettability of the PET nonwoven was enhanced due to plasma treatment which was evident from considerable decrease in water contact angle results and increase in the proportion of polar groups, in particular carboxyl –O–C=O– groups.

On the other hand, super-hydrophobic, self-cleaning nonwoven surfaces have been produced by imparting of oxides such as TiO2 and a polymethylsiloxane coating on cellulose via CVD technique [12]. Sobczyk-Guzenda et al. [44] used radio frequency plasma-enhanced chemical vapor deposition technique to deposit thin TiO2 film (Fig. 10) on cotton fabric to impart a selfcleaning effect under UV illumination through a photooxidizing activity.

**Figure 10.** Scanning electron microscope picture of plasma deposited TiO2 coating on cotton fabric [44]

the aqueous liquid and subsequent drying of the fabric. In such case, the surfactants are effective in rendering the fabric wettable for a limited time during the use of the product. Surface treatment of nonwoven fabrics using plasma is an alternative method to improve their

**Figure 9.** C1s peak of untreated and oxygen plasma treated sample at 80 watt and 10 minutes, (A1) PP untreated, (A2)

PP oxygen plasma treated, (B1) cotton untreated, (B2) cotton oxygen plasma treated [29]

Behary et al. [43] activated the surface of a carded and hydroentangled PET (polyethylene terephthalate) nonwoven by an air–dielectric barrier discharge atmospheric plasma. The wettability of the PET nonwoven was enhanced due to plasma treatment which was evident

wettability [41].

224 Non-woven Fabrics

The surface wetting of the nonwoven materials was changed by deposition of different materials through sputtering. Wei et al. [10] performed the deposition of copper, zinc oxide (ZnO), and polytetrafluoroethylene (PTFE) on the surface of polypropylene meltblown nonwoven through sputtering. While copper coating improved the surface conductivity of the material, ZnO coating significantly increased the UV absorption of the material necessary for UV shielding. Both Cu and ZnO coating rendered the nonwoven surface hydrophilic. Depo‐ sition of PTFE provided surface hydrophobicity on the nonwoven material due to increase in surface contact angle and roughness [10]. Sputter coatings of copper and silver on spunbonded polypropylene nonwovens provided reduced transmittance both in UV and visible light ranges [20].

Deng et al. [45] and Wei et al. [46] reported a decrease in electrical resistance of aluminum and copper sputtered polypropylene spun-bonded nonwovens. Aluminum-doped zinc oxide (AZO) and doped indium oxide (ITO) films were deposited onto the polypropylene nonwo‐ vens by magnetron sputtering. For the same thickness, nonwoven materials coated with ITO showed a lower electrical resistance than those coated with AZO. The nanoscale AZO coating on nonwoven provided better UV protection than ITO coating for the same thickness [20]. Jianfeng et al. [47] studied the electromagnetic shielding efficiency of PET nonwovens by sputtering of nanoscaled Cu, Ag, Ag/Cu, and Ag/Cu/Ag films.

In another study, Baek et al. [48] used microwave-induced argon plasma to modify and sputtercoat the surface of nanofibrous silk fibroin scaffolds with gold/platinum to enhance the attachment and proliferation of the human articular chondrocyte cultures.

Nonwovens currently find applications in various industries such as medical and hygiene, home textiles such as mattresses, floor coverings, and shoe linings. A suitable environment for infection by microorganisms is created especially in nonwoven products used in hospitals, hotels, and the clothing of the personnel. Nonwovens made from natural fibers such as cotton are more susceptible to bacterial proliferation than synthetics due to the moisture content of natural fibers.

Antibacterial property has been imparted to nonwovens by the application of antibacterial finishes such as metallic ions of silver [40, 49], copper, and their compounds, also phenols, quaternary ammonium salts, and organosilicones. Nontoxicity of the antibacterial agent becomes critical depending on the end-use of the product.

Mazloumpour et al. [50] used atmospheric pressure glow discharge plasma to impart antimi‐ crobial properties to a polypropylene spun-bond nonwoven. A durable antimicrobial property was achieved on the nonwoven by plasma grafting of diallyldimethylammonium chloride (DADMAC) in the presence of a cross-linker.

Several studies showed metal, that is, silver, sputtering onto polypropylene and polyester nonwovens and polyacrylonitrile electrospun nonwovens to impart antibacterial property [51, 52, 53]. Shahidi et al. [16] deposited copper onto the surface of cotton fabric samples by DC magnetron sputtering for antibacterial effect and found that duration of the application process was shorter compared to conventional application processes using nonionic detergent and metallic salts. The obtained antibacterial effect was found to be durable against 30 washing cycles.

Plasma deposition has also been used to impart flame retardancy to nonwovens. Acrylate monomers containing phosphorus have been plasma grafted on cotton and PET/cotton fabrics. Plasma enhanced chemical vapor deposition of an organosilicon thin film on polyamide 6 has been performed using the cold remote nitrogen plasma process [54].
