Abstract
Poly (Vinyl Alcohol) (PVA) is used to produce nanofibers with electrospinning for several applications related to the non-toxicity of the material, however, the application in air filtration in hindered by the high hydrophilicity of the material, which requires the crosslinking with additives. In this work, different techniques were assessed to verify the moisture resistance of PVA nanofibers crosslinked with citric acid. The mass loss did not reveal significant structural modification of the filter media due to the relatively low mass of the nanofibers in comparison to the mass of the substrate, proving the poor applicability of this technique for this process. The measurement of the water contact angle was not suitable for the experimental circumstances as well. A methodology was then purposed, measuring the pressure drop before and after the flow of clean air stream (~15.0 cm s-1) through the filter media with different contents of water (49, 68, and 90% R.H.) to verify the humidity resistance of the fibers over time (zero to 60 min). The samples were resistant to humidity and no significant structural changes occurred in the fibers after the process in accordance with analysis of scanning electron microscopy images. For the two lowest humidities, variation of the pressure drop was equal to approximately zero after 60 min while it achieved 4.1% for 90% R.H. This methodology proved to be suitable for air filtration application.
Highlights
Poly(vinyl alcohol) (PVA) fibers produced with the electrospinning technique are currently used in tissue scaffolds with antimicrobial activity (Esparza et al, 2017; Hong et al, 2006; Tonglairoum et al, 2015), filtration of gases (Zhu et al, 2018), and liquids effluents (Bary et al, 2018; Li; Barbari, 1995; Li; Yao, 2017), as an option to polymers that are soluble in harmful solvents such as dimethylformamide (DMF)
The mass loss after immersion in water (Esparza et al, 2017; López-Córdoba et al, 2016; Lv et al, 2019; Miraftab et al, 2015; Shi; Yang, 2015; Stone et al, 2013) and water contact angle measurements (Fang et al, 2018; Lee et al, 2016) are traditionally used to evaluate the resistance to water, these methodologies seem not attesting the usefulness of the PVA filter media in air filtration, a process in which water could be present as moisture in the air stream, but there is no severe condition like immersion in pure water
Following the experimental procedures described before, the properties of the PVA solution were obtained: the viscosity was equal to 3.54 ± 0.03 (Pa×s), the electrical conductivity was equal to 772 ± 2, and the surface tension was equal to 34.3 ± 0.4
Summary
Poly(vinyl alcohol) (PVA) fibers produced with the electrospinning technique are currently used in tissue scaffolds with antimicrobial activity (Esparza et al, 2017; Hong et al, 2006; Tonglairoum et al, 2015), filtration of gases (Zhu et al, 2018), and liquids effluents (Bary et al, 2018; Li; Barbari, 1995; Li; Yao, 2017), as an option to polymers that are soluble in harmful solvents such as dimethylformamide (DMF). PVA presents high degree of hydrophilicity due to the presence of hydroxyl groups in the polymer chains, hindering its use in the filtration of liquids and humid gases. The mass loss after immersion in water (Esparza et al, 2017; López-Córdoba et al, 2016; Lv et al, 2019; Miraftab et al, 2015; Shi; Yang, 2015; Stone et al, 2013) and water contact angle measurements (Fang et al, 2018; Lee et al, 2016) are traditionally used to evaluate the resistance to water, these methodologies seem not attesting the usefulness of the PVA filter media in air filtration, a process in which water could be present as moisture in the air stream, but there is no severe condition like immersion in pure water
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