- Plasticized starch is a modified form of starch that has been processed with plasticizers to enhance its flexibility, workability, and mechanical performance.
- Native starch, obtained from renewable sources such as corn, potato, cassava, or wheat, is a biodegradable and inexpensive polymer. However, in its natural state, starch is brittle, hygroscopic, and difficult to process using conventional thermoplastic techniques. By introducing plasticizers—typically small molecules such as water, glycerol, sorbitol, or urea—the rigid hydrogen-bonding network within starch granules is disrupted. This reduces intermolecular forces and increases chain mobility, allowing starch to behave like a thermoplastic material, commonly referred to as thermoplastic starch (TPS).
- The plasticization process is usually carried out through melt extrusion, compression molding, or solution casting, where starch is heated in the presence of the chosen plasticizer. The resulting material exhibits enhanced ductility, improved processability, and reduced brittleness compared to native starch. Plasticized starch can be extruded, blown into films, or injection-molded, making it compatible with traditional polymer processing equipment. The degree of plasticization, and therefore the final properties of the material, depends on factors such as the type and concentration of plasticizer, moisture content, and processing conditions.
- Despite its improved flexibility, plasticized starch is still sensitive to retrogradation, a phenomenon where starch chains re-crystallize over time, leading to increased brittleness and loss of mechanical integrity. To overcome this limitation, plasticized starch is often blended with other biodegradable polymers (such as polycaprolactone, polylactic acid, or polyhydroxyalkanoates) or reinforced with natural fibers and nanofillers to improve stability, mechanical strength, and barrier properties. These modifications expand its potential applications in packaging, disposable items, agricultural films, and biomedical materials.
- From a sustainability perspective, plasticized starch is an attractive alternative to petroleum-based plastics because it is renewable, biodegradable, and compostable. Its end-of-life pathways include natural degradation in soil and water, making it a promising candidate in addressing environmental concerns associated with plastic waste. However, its industrial use is still limited due to challenges like moisture sensitivity, retrogradation, and relatively poor mechanical performance compared to synthetic plastics. Ongoing research focuses on improving these properties while maintaining the ecological advantages of plasticized starch.
