**3. Plasma treatment for enhancement of adhesion properties of nonwovens**

Surface modification of textiles by plasma treatment has been used for the adhesion enhance‐ ment of fibers and fabrics. Introduction of functional groups at the fiber surface helps to form affinity or chemical bonds with a coating material leading to an adhesion improvement [33, 34, 35]. For instance, Šimor et al. [36] used atmospheric-pressure nitrogen plasma as a pre‐ treatment to render the surface of polyester nonwoven fabric hydrophilic for subsequent electroless nickel plating.

However, bonding should be immediately performed following plasma treatment, since storage may result in a reduction or loss of adhesion to the treated surface [6].

Rombaldoni et al. [33] used low-temperature oxygen plasma treatment to enhance the adhesion between polypropylene nonwoven and poly(ethylene oxide) and polyamide-6 nanofibrous mats deposited onto polypropylene nonwoven. Improvement of adhesion between the nonwoven and the nanofibrous coatings was reported, which was attributed to the increased wettability of the supporting polypropylene fabric and polar functional groups introduced by plasma treatment allowing a stronger interaction between the treated fabric and coatings [33, 35].

Li et al. [37] fabricated a high-performance battery separator where they used polypropylene nonwoven as the support material. A fluorinated polymer, octafluoropentyl methacrylate, was grafted onto the surface of the polypropylene nonwoven by plasma treatment to improve the nonwoven's adhesion with poly(vinylidene fluoride-co-hexafluoropropylene).

The adhesion (peel bond) strength between two layers of polypropylene spun-bonded nonwovens, plasma treated and laminated by polyurethane-based adhesive, was improved by up to 150% compared to that of the untreated laminated samples [38, 39]. This was attributed to the increased surface roughness of the polypropylene fibers due to the etching effect of the plasma treatment (Fig. 7), leading to enhanced mechanical adhesion between the laminated layers.

**Figure 7.** SEM images of PP fibers, (a) untreated (×5060) and (b) treated by argon plasma at 80 W for 10 min (×5490) [38]

The plasma-induced changes in surface morphology of polypropylene fibers of a spun-bonded nonwoven on the nanometer scale was demonstrated by [40] via AFM (atomic force micro‐ scopy) analysis (Fig. 8). It was found that plasma treatments increased the fiber surface area and surface roughness due to fiber etching by the bombardment of the fiber surface by plasmagenerated energetic particles and reactive particles.

34, 35]. For instance, Šimor et al. [36] used atmospheric-pressure nitrogen plasma as a pre‐ treatment to render the surface of polyester nonwoven fabric hydrophilic for subsequent

However, bonding should be immediately performed following plasma treatment, since

Rombaldoni et al. [33] used low-temperature oxygen plasma treatment to enhance the adhesion between polypropylene nonwoven and poly(ethylene oxide) and polyamide-6 nanofibrous mats deposited onto polypropylene nonwoven. Improvement of adhesion between the nonwoven and the nanofibrous coatings was reported, which was attributed to the increased wettability of the supporting polypropylene fabric and polar functional groups introduced by plasma treatment allowing a stronger interaction between the treated fabric and

Li et al. [37] fabricated a high-performance battery separator where they used polypropylene nonwoven as the support material. A fluorinated polymer, octafluoropentyl methacrylate, was grafted onto the surface of the polypropylene nonwoven by plasma treatment to improve the

The adhesion (peel bond) strength between two layers of polypropylene spun-bonded nonwovens, plasma treated and laminated by polyurethane-based adhesive, was improved by up to 150% compared to that of the untreated laminated samples [38, 39]. This was attributed to the increased surface roughness of the polypropylene fibers due to the etching effect of the plasma treatment (Fig. 7), leading to enhanced mechanical adhesion between the laminated

**Figure 7.** SEM images of PP fibers, (a) untreated (×5060) and (b) treated by argon plasma at 80 W for 10 min (×5490)

The plasma-induced changes in surface morphology of polypropylene fibers of a spun-bonded nonwoven on the nanometer scale was demonstrated by [40] via AFM (atomic force micro‐ scopy) analysis (Fig. 8). It was found that plasma treatments increased the fiber surface area

storage may result in a reduction or loss of adhesion to the treated surface [6].

nonwoven's adhesion with poly(vinylidene fluoride-co-hexafluoropropylene).

electroless nickel plating.

222 Non-woven Fabrics

coatings [33, 35].

layers.

[38]

**Figure 8.** AFM images of (a) untreated and (b) dielectric barrier discharge plasma-treated spun-bonded polypropylene fabric [40]

Armağan et al. [29] reported about 28–60% improvement in the adhesion (peel-off) strength of oxygen plasma pretreated and laminated cotton/polypropylene fabrics using an acrylicbased adhesive compared to untreated laminated samples. After 40 washing cycles, an improvement in peel-off strength of plasma pretreated and laminated samples compared to that of untreated laminated samples was also reported. The improvement was attributed to the increased wettability of the surfaces with oxygen plasma treatment contributing to the adequate wetting of the surface by the adhesive. Functional groups introduced to the fiber surface resulted in better interaction between the adhesives and the plasma-pretreated fabric surface.

The change of the functional side groups on a polypropylene spun-bonded nonwoven after oxygen plasma treatment was determined by high-resolution XPS analysis of C1s peaks [29]. It was observed that the amount of C–C/C–H group decreased, while the amount of oxygenrelated groups increased (Fig. 9) after the plasma treatment, rendering the fabric surface more wettable.
