Reinforcement Materials and Processing of Starch‐Based Composites for Rigid and Semi‐Rigid Food Packaging

ABSTRACT Starch is a natural, renewable, and low‐cost biopolymer with promising potential to replace petrochemical plastics in food packaging applications. Starch as a polymeric matrix offers a wide range of possibilities for improvement, making it more attractive to use in various applications in rigid/semi‐rigid packaging than other biodegradable materials such as cellulose‐based paper/cardboard or polylactic acid (PLA). Thermoplastic starch (TPS) processing under optimized plasticization conditions allows suitable mechanical properties (tensile strength: 2–15 MPa; elongation at break: 10%–150%). However, native starch exhibits high hydrophilicity and poor thermal stability. This review critically evaluates TPS performance for rigid/semi‐rigid food packaging applications, such as mechanical strength, moisture barrier, thermal stability, and structural integrity, and discusses advanced reinforcement strategies. These include nanofillers (starch/nanocellulose composites achieving Young's modulus > 3 GPa), natural fibers (e.g., 20% hemp fiber increasing tensile strength by ~200%; thermal stability improvement up to 50°C with lignocellulosic fibers), nano clays (WVTR reduction by 30%–70%) and polymer blending (e.g., TPS/PLA mixtures with 10% lower moisture absorption). Processing techniques (extrusion, injection, compression molding) and interfacial compatibility (e.g., silane coupling agents that improve adhesion between filler and matrix) are also analyzed. Finally, the main challenges of industrial adaptation to advance starch‐based packaging toward high‐performance biodegradable applications are addressed.