<i>In-Situ</i> Monitoring of Solidification Process of PVA Solution by Fiber Optic Sensor Technique

Zhou, Fengfeng; Tsai, Jung-Ting; Jo, Seunghwan; Kım, Garam; Lee, Patrick; Jun, Martin Byung‐Guk

doi:10.1109/jsen.2020.3040571

Cited by 7 publications

(1 citation statement)

References 25 publications

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“…As a result, a concentration gradient gradually emerges from top to bottom of the solution, leading to the creation of structural heterogeneity in the dried film, known as a “skin-core” structure. − The nonuniformity between the skin and core areas can reduce the mechanical properties. , Besides, the formation of the skin may trigger buckling instability. − Shrinkage stresses that arise on the film surface during the drying phase are alleviated through the formation of cracks. − There is a possibility of the film interior detaching spontaneously from the substrate, thereby impacting industrial production. In addition, the inconsistency in the index of refraction between the skin and core layers leads to heterogeneity in the optical properties of the base film. − Consequently, it is essential to manage the structural transformation that occurs during the film formation process and mitigate the structural nonuniformity of the film to guarantee a successful casting.…”

Section: Introductionmentioning

confidence: 99%

Suppression of the Skin-Core Structure of Poly(vinyl alcohol) Films by Adding Urea/Diethanolamine to Improve the Mechanical and Optical Properties

Li,

Liu,

et al. 2024

Macromolecules

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The microstructure of poly(vinyl alcohol) films formed during the solution drying process significantly influences their tensile ductility and optical transmittance. However, the "skin-core" structure of the dried PVA film is very obvious since the PVA solution dries extremely fast at a relatively low initial concentration (C 0 ). Herein, we propose a strategy to reduce the evaporation rate through the incorporation of plasticizer-type additives. For this purpose, urea and diethanolamine (DEA) were selected as the compound additives. On the one hand, the solubility of urea in water was improved by DEA because DEA is a good solvent for urea. On the other hand, more intermolecular hydrogen bonds were formed between the primary amine groups on urea and the hydroxyl (−OH) groups on PVA. The formation of PVA−plasticizer hydrogen bonding networks significantly prolonged the deceleration drying period and slowed down the drying process of the solution. In addition, the reduction in the content of single hydrogen-bonded water also favored the acquisition of a homogeneous structure. When the content of the urea/DEA compound additives was over 10%, the "skin-core" structure was suppressed. The structural changes in films have had an impact on both mechanical and optical performances. The fracture strain of the modified PVA film reaches 448.2%, and the average light transmittance in the visible range reaches 97.8% when the content of the compound additive is 20% of the PVA mass. These values are much higher than those of the control film, which are 9.2 and 92.2%, respectively. This study enhances comprehension of the film-forming mechanism and structural changes in PVA/H 2 O/plasticizer systems, offering theoretical insights for improved industrial processing.

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