Development of a Continuous Extrusion Process for Alginate Biopolymer Films for Sustainable Applications

This study presents a novel method for producing extrudable alginate-based films using continuous thermo-mechanical mixing, providing a scalable alternative to conventional solvent-casting techniques. The effects of glycerol concentration (30-50 wt%) and processing temperature (110-120 °C) on the films' thermal, mechanical, and structural properties were systematically investigated. Structural characterization was performed using ¹H NMR and FT-IR, and thermal transitions were analyzed via DSC (Differential Scanning Calorimetry) and DMA (Dynamic Mechanical Analysis). The glass transition temperature (Tg) of the alginate/glycerol/water system was modeled using the Gordon-Taylor equation. Glycerol incorporation significantly reduced Tg-by up to 76 °C with 40 wt% glycerol-and enhanced ductility and toughness, reaching 3.26 MJ/m³ at the optimal level. The influence of processing temperature was found to depend on plasticizer content: at lower glycerol levels, elevated temperatures decreased Tg and elongation at break, likely due to thermal degradation. However, films with higher glycerol content retained stable mechanical and thermal behavior across both temperature profiles. This work is among the first to explore how processing temperature affects extruded, plasticized pure alginate films. The findings provide key insights into the formulation and scalable production of bio-based packaging materials, highlighting the importance of optimizing both plasticizer concentration and processing parameters.