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    Controlling unequal surface energy results caused by test liquids: the case of UV/O3 Treated PET
    (Nature Portfolio, 2022) Altay, Bilge Nazli; Fleming, Paul D.; Rahman, Md Arifur; Pekarovicova, Alexandra; Myers, Bruce; Aydemir, Cem; Karademir, Arif
    Ultraviolet/ozone (UV/O-3) treatment has been reported to be an effective method to modify properties such as wettability, adhesion or adsorption of plastic surfaces. The change in the surface is measured by contact angle analysis, which employs liquids and their surface tensions (ST) to estimate the surface energy (SE). We found two different practices in the scientific community: (1) the majority of researchers adopted the ST value of liquids from the literature, while (2) other researchers conducted real-time measurements in the lab under ambient conditions prior to SE estimation. To the best of our knowledge, there is no study that compares the difference between the two practices. One study was found to show different SE methods generating unequal SE values for the same substrate. However, there was no definitive conclusion backed by general thermodynamics rules. In this study, we presented (1) a statistical significance test that showed the literature and experimental ST values are significantly different, and studied (2) the effect of different liquid pairs on the SE estimation for UV/O-3 treated poly(ethylene terephthalate) (PET) substrate. Modification techniques such as atmospheric pressure plasma or chemical modification were studied previously to examine PET's wettability and the SE. The UV/O-3 treatment was studied to improve adhesion and to modify its chemical properties for adsorption. In contrast, we studied (3) the effect of UV/O-3 on wettability at different timeframes and addressed (4) how to control unequal SE based on a method that was refined on a rigorous thermodynamic three-phase system. It must be noted that this method can be generalized to other types of solid surfaces to estimate thermodynamically self-consistent SE values. This work also provides (5) a web-based calculator that complements computational findings available to the readership in the data availability section.
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    Enhanced Internal Coating Structure and Light Reflectance of Coated Papers: A Sludge Valorization Process
    (Amer Chemical Soc, 2023) Altay, Bilge Nazli; Huq, Anamika; Aksoy, Burak; Hailstone, Richard; Demir, Muslum; Aydemir, Cem; Williams, Scott
    Paper mill sludge (PMS) is a high-volume waste of the pulppapermaking industry, containing cellulose fibers. This paper introduces cellulose nanofibers extracted from PMS (CNFsPMS) and their application in paper coatings using a wire-wound coating method to enhance internal and optical properties of paper. Three factors were investigated: (i) CNFsPMS amount, (ii) number of layers, and (iii) surface treatment via a 4 x 2 x 2 factorial design. The experimental responses were tracked by fundamentally important internal properties including porosity, air permeability, thickness, roughness, and optical properties of brightness, gloss, and CIE L*a*b* color coordination. The results showed that CNFPMS enhances porosity to 91 mL/ min, permeability to 0.5 x 10-3 mu m2, and gloss to 29.5 at 1 wt % CNFsPMS applied in two layers with 500 pli calendering. Roughness improves to 2 mu m at all levels of CNFsPMS applied to two layers with 500 calendering. CNFsPMS prevents a decrease in brightness and improves lightness, suggesting more colors can be produced in printing applications. The utilization of PMS for papermaking applications can add value to these underutilized residues and open a new revenue stream by reusing it as a high-value material.
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    Investigation of the evolution of hydrophobicity and wettability of paper in multi-color printing process
    (Editura Acad Romane, 2019) Aydemir, Cem; Karademir, Arif; İmamoğlu, Sami; Altay, Bilge Nazli; Fleming, Paul D.; Tutak, Dogan
    One of the keys to improving print quality is to experimentally characterize the paper surface, structure and printability to obtain quality control mechanisms. In multi-color prints, determining the differences in the acceptance of the next color ink by the surface of the paper or the ink film that was previously printed is important for print quality. The criteria, such as ink setting, adhesion, color, gloss and density, in the printing process, depend on the wettability and absorbency of the paper. The surface structure of the paper is the most important factor in determining the hydrophobic properties. In this study, wetting and absorption dynamics of the printed partially hydrophobized paper surface were investigated. The aim was to measure the effect of the printed ink film on the wetting (surface free energy) and liquid absorption behavior of the paper. Liquid absorption changes on printed/unprinted paper surfaces were measured by the sessile drop method, using a contact angle-measuring device. The surface energies of the papers were calculated and evaluated according to the surface contact angle of the droplet.