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Author: search.filters.author.Munpiriyakul, PimpapornHas files: No

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    Size-dependent and spatial variations in the structural properties of spin-coated poly(Vinylidene Fluoride) films
    (2025-10-01)
    Sukjit, Peemases
    ;
    Munpiriyakul, Pimpaporn
    ;
    Tuantranont, Adisorn
    ;
    Lomas, Tanom
    ;
    Borthai, Pawantree
    The uniformity of structural properties in large spin-coated poly(vinylidene fluoride), or PVDF, films is crucial due to their widespread applications and thus requires careful investigations. In this study, variations in structural properties across PVDF films of different sizes and positions were examined. Thin PVDF films were fabricated by the spin-coating method onto rectangular substrates with lengths varying from 10 mm to 40 mm while maintaining a constant width of 10 mm. Three key characteristics – thickness, phase, and crystallinity – were characterized and analyzed. Two effects were investigated – the size-dependent effects, i.e., the property variations at a specific position due to the increasing film length, and the spatial effects, i.e., the property variations along distances from the film center within a film of a specific size. The average thickness of the fabricated film was in the range of 5.00 μm to 6.00 μm, while the crystalline size was in the range of 1.00 nm to 3.00 nm. For the size-dependent effects, at a specific position on the film, increasing the film length did not significantly affect the thickness; however, the phase of PVDF shifted toward a more chain-like β phase, while the crystalline size decreased. At the film center, the crystalline size decreased by 60.7% when the film size increased from the smallest to the largest. These changes resulted from four combined mechanisms: centripetal force, viscosity, evaporation rate, and shear force. For the spatial effects, in a film with a specific size, when the distance from the center increased, the thickness decreased, the phase remained β, and the crystalline size was smaller. For the largest 40 × 10 mm<sup>2</sup> film, the thickness and crystalline size decreased by 16.7% and 3.6%, respectively, from the center to the edge of the film. These trends were attributed to the three combined mechanisms: centripetal force, viscosity, and evaporation rate. The findings of this study provide critical insights into a deeper understanding of property variations in spin-coated PVDF films among both different film sizes and different positions on a film, which is essential for optimizing their applications.
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    Advanced chitosan hybrid dye labels for dynamic monitoring of shrimp and milk freshness
    (2025-04-01)
    Ronte, Arnat
    ;
    Chalitangkoon, Jongjit
    ;
    Sintoppun, Tanaporn
    ;
    Niemhom, Nantawan
    ;
    Manapradit, Nuttaporn
    This study presents the development of intelligent screen-printed labels for real-time food freshness monitoring. Using chitosan grafted with rosolic acid (RA) and immobilized on montmorillonite (MMT) through cationic exchange, a hybrid dye was synthesized and applied in screen-printing inks. The hybrid structure was characterized by XRD, TGA, and UV–vis, confirming improved thermal stability and maintained halochromic properties. SEM analysis showed consistent ink deposition on filter paper, while water contact angle (WCA) measurements demonstrated enhanced surface hydrophobicity due to the MMT. The labels exhibited clear pH-sensitive color transitions from yellow to purplish red (pH 2.0–12.0) and rapid ammonia sensitivity, with ΔE values exceeding 45.0 within 10 min. The labels also demonstrated excellent reversibility, storage stability, leaching resistance, and cytocompatibility. Practical tests on shrimp and milk confirmed the labels' ability to accurately monitor freshness through visible color changes. These findings highlight the potential of hybrid labels as effective, scalable freshness indicators for intelligent food packaging.
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    Characterization of Thin Diamond-Like Carbon Layer Coverage by Trace Metal Leaching Test
    (2017-01-01)
    Munpiriyakul, Pimpaporn
    ;
    Siriwongrungson, Vilailuck
    ;
    Brothers, Alan
    ;
    Supadee, Laddawan
    ;
    Waengwan, Pattamart
    A trace metal leaching test was applied to investigate coverage of a diamond-like carbon layer. Three trace metals - cobalt, nickel and iron - were measured. The change of seed and diamond-like carbon thicknesses influenced the trace metal concentration detected due to the passivation of the substrate via pinholes. Artificial pinholes were applied for a diamond-like carbon pinhole study, and it was found that the diameter, shape and total surface area of the holes affected the trace metals detected. The surface morphology and thickness were examined using scanning electron microscope and transmission electron microscope. The passivation was analyzed using electron energy loss spectroscopy.