Hydrophobic Coating on Woven Material for Personal Protective Equipment

The performance of personal protective equipment fabrics for COVID-19 health care practitioners was improved by polyvinyl alcohol (PVA) coating. The PVA enhances fabric’s resistance to body fluid penetration, on the other hand, also increases its hydrophilic properties. However, hydrophobic is required to prevent microdroplets and body fluid wetting on the fabrics. The hydrophobic effect was increased by immersed the fabrics in silica nanoparticles that resulted in a water contact angle of 133.41° ± 10.8°.


Introduction
An increasing number of people infected by the viral spread of Covid-19 has proportionally increased the demand for personal protective equipment (PPE). Especially, PPE is necessary for health workers who deal with a higher risk of infection. For spread prevention of Covid-19 infection, people need at least a mask protection [1]. Therefore, wearing PPE is feasible to control and prevent disease transmission [2].
The complete PPE kit includes a face shield, goggles, mask, gloves, head cap, shoe covers, combined with a gown or coveralls [3]. The Covid-19 coveralls for viral protection materials typically used are polypropylene, polyester, polyethylene, and cellulose in forms of nonwoven or woven fibers [4], because these materials potentially fulfill the required properties for coveralls like durability, hydrophobicity, and permeability [5].
Initial fabrics pore condition was permitted water penetration and microorganism. On the other hand, Polyvinyl alcohol (PVA) coating is a hydrophilic polymer with excellent film-forming properties that cover fabric pores [3]. The presence of hydroxyl groups on PVA treated fabric might increase the wetting behavior [6]. Because of improved hydrophilicity of PVA coated fabric, PPE hydrophobicity is desirable to prevent microdroplet and body fluid attachment on fabrics surface [7].
Hydrophobicity of PPE materials was measured by a contact angle between a water droplet and fabric surface that defined as a water contact angle (WCA). The WCA of hydrophilic and hydrophobic effect on the surface of the fabric are indicated with values lower than 90° and higher than 90°, respectively [8]. The maximum 156.84° ± 1.5° WCA of the fabric with superhydrophobic properties was achieved on a cotton surface coated using SiO2 nanoparticles and PVA with boric acid as the  [9]. In this study, adsorption of nano-silica after PVA coating was conducted to observe the hydrophobic effect of the treated fabric.

Preparation of PVA Solution
PVA solution was prepared by mixing PVA with 200 mL deionized water and heated to a temperature of 80℃ for 1,5 hours in a 500 mL (Catalogue Number TE32, Asahi Glass, Indonesia) beaker and stirred about 300 to 400 rpm using a 6 cm magnetic stirrer bar. The solution then was conditioned at room temperature to dissolved bubbles that were obtained during stirring.

Preparation of Woven Fabrics
The woven fabric with a size of 7.5 × 7.5 cm was soaked into 15% wetting agent Teepol solution for 15 minutes followed by air-dried for 3-5 minutes. Then, the PVA solution was coated on the fabrics by poured the solution on dried fabrics and padded with a roller pad. Next, coated fabrics are cured in a 160℃ oven for 50 minutes. The cured coated fabric then was soaked in 10% SB-nano-silica for 15 minutes and dried again in a 120℃ oven for 20 minutes.

Characterization
Hydrophobicity of the coated fabric as indicated by water contact angle (WCA) value, was measured by taking images of 5µL water droplets with a DSLR camera (Nikon D700, Minato-ku, Tokyo, Japan). The formed droplets angle image was measured with FIJI ImageJ Software [10]. Formation of functional groups between PVA, SB-nano-silica, and the fabric was measured by Fourier transform infrared (FTIR) spectroscopy on (Perkin Elmer, Spectrum 2 FTIR).

Water Contact Angle (WCA)
The initial average WCA value prior fabric/PVA coated is 55.65° ± 5.3°. The average WCA value post fabric/PVA soaked in SB-nano-silica solution is 133.41° ± 10.8°. Results indicated that posttreatment improved the hydrophobicity of the fabric (Figure 1). With visual illustration between initial and treated fabric condition is shown in Figure 2.     [6]. The peak at 1086 cm -1 , 844 cm -1 , and 472 cm-1 for PVA and SB-nano-silica treated fabric shows Si−O−Si asymmetrical stretching band, symmetric stretching, and bending vibrations bands, respectively (blue plot) [12]. The peak at 3298 cm -1 not as strong as the fabric/PVA, indicates hydroxyl groups have condensation to form silanol bridges.

Conclusion
Hydrophobic coating on woven fabric has increased the water contact angle of treated fabric and functional groups confirmed by FTIR analysis. This treated fabric could be potential as the raw material for personal protective equipment. Further research and development are required to improve prototyping and industrial scale-up process.