Browsing by Author "Ellinas, Kosmas"

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    Fabrication of Superhydrophobic Yogurt Packaging Polymers via Hot Embossing
    (MDPI- Processes, 2026-10-27) Inhensiko, Derrick Emanuel; Nakyinsige, Khadijah; Mukama, Matia; Gianneli, Nektaria-Anastasia; Karathanasi, Konstantina; Giaouris, Efstathios; Ellinas, Kosmas
    Yogurt adhesion to plastic packaging surfaces contributes significantly to product wastage, poor emptiability, and consumer dissatisfaction, which highlights the need for advanced non-stick food packaging solutions. In this study, commercially used yogurt containers made of polypropylene (PP) and low-density polyethylene (LDPE) sourced from Ugandan and Greek markets were engineered into non-stick surfaces through a combination of hot embossing and subsequent hydrophobic coating. Hot embossing successfully transferred hierarchical micro/nano-scale textures onto the polymer surfaces, increasing average surface roughness from 0.79–1.65 µm to 2.27–5.12 µm (p < 0.05), with LDPE exhibiting the highest texture replication. These morphological changes resulted in a marked transition in wetting behavior, with water contact angles (WCAs) increasing from 69.6–100.3° on untreated surfaces to 143.1–160.5° after embossing, accompanied by a significant reduction in contact angle hysteresis (CAH) from 23.9–64.6° to 4.5–23.3°. Subsequent hydrophobic coating further reduced surface free energy, yielding superhydrophobic surfaces with contact angles up to 171.6° and ultra-low hysteresis values as low as 3.6°, consistent with a superhydrophobic wetting state. The combined physical (hierarchical roughness) and chemical (low surface energy) modifications significantly reduced yogurt adhesion and enhanced surface cleanability across all polymers. Bacterial recovery results did not demonstrate antibacterial activity; rather, Teflon™ AF 1600-treated surfaces generally showed higher recoverable viable bacterial counts than untreated surfaces. Principal component analysis further showed associations between surface roughness, water contact angle (WCA), contact angle hysteresis (CAH), yogurt angle (YCA), and recovered bacterial counts. Overall, this work demonstrates a scalable and effective strategy for transforming conventional yogurt packaging into superhydrophobic and non-stick systems, offering a practical pathway toward smart and sustainable dairy packaging with reduced food waste and an improved consumer experience.