ABSTRACT

This study investigates the fabrication of agar-glycerol films via compression moulding, a scalable thermal processing technique. The objective is to investigate the properties of thermally processed agar films by varying the type of calcium counter ions: adding calcium stearate (CS) to increase hydrophobicity, while calcium chloride (CaCl2) to promote its degradation. The study includes different types of films with varying glycerol amounts, along with different levels of CS and CaCl2 represented by these codes (HGCS25Ca5, HGCa25CS5, LGCS25Ca5 and LGCa25CS5) refer to the specific film samples used in this study. The impact of these compositional variations on thermal behaviour, surface characteristics and degradation profiles is rigorously assessed. The highest melting peak (Tₚₑₐₖ) observed was 140°C, achieved by the formulation containing high CaCl₂ (HGCa25CS5), indicating the crosslinking of CaCl₂ with agar contributes to an increase in the melt transition temperature. The LGCa25CS5 and HGCa25CS5 have higher residual char, approximately 28.42% and 23.37% compared with agar films without CS and CaCl2 (7.49%–8.97%), which implies that the material decomposes less, indicating better thermal stability. The highest contact angle (110.053°) was observed in low glycerol formulations containing high CS, which contributes to enhanced surface hydrophobicity. Conversely, CaCl2, while contributing to the structural integrity of the film, exhibited a less pronounced effect on surface hydrophobicity. High glycerol (HG) sample showed a weight loss of 15.80%, while the thermal compressed agar film incorporating CS and CaCl2 exhibited the highest weight loss of 90%, indicating that CS and CaCl2 promote oxidative degradation of agar chains, enhancing the film’s susceptibility to microbial degradation and resulting in increased weight loss during soil burial tests. The weight loss of all films in the vermicompost condition is more pronounced than in the soil condition. These findings highlight the potential of compression moulding to produce agar-based films with adjustable properties by carefully adding CS and CaCl2. This approach offers a useful understanding of how these additives influence thermal stability, surface hydrophobicity and degradation behaviour in agar-glycerol systems.

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