How does glycerol, as a plasticizer, affect the flexibility of Cornstarch Bioplastic Biobased Tray during its production process?

In the production process of Cornstarch Bioplastic Biobased Tray, glycerol as a plasticizer mainly affects its flexibility through the following mechanisms:

1. Weakening of intermolecular forces
Glycerol is a small molecule plasticizer that can insert between polymer chains of starch or polyvinyl alcohol (PVA), and bind to polymer molecules through hydrogen bonding and van der Waals forces. This will reduce the strong hydrogen bonding between starch molecules, decrease the attraction between molecular chains, thereby enhancing the mobility of molecular chains and significantly improving the flexibility and extensibility of the material.

2. Filling effect and lubrication effect
Glycerol fills the gaps between starch and PVA, providing lubrication, reducing friction between molecular chains, and promoting chain sliding. This filling effect not only increases the free volume of the material, but also makes the molecular chains easier to stretch under force, thereby improving flexibility.

3. Water regulation and hydrophilic effect
Glycerol has hydrophilicity and can retain moisture through moisture absorption, preventing materials from becoming brittle due to drying. At the same time, an appropriate amount of glycerol will form stronger glycerol polymer bonds, inhibiting excessive water infiltration into the material, thereby balancing flexibility and structural stability.

4. Concentration dependence
There is an optimal concentration range for the plasticizing effect of glycerol. Research has shown that a glycerol content of 30% can significantly enhance the strength and flexibility of thermoplastic starch (TPS), but exceeding this concentration can lead to a decrease in mechanical properties.

5. Synergistic effects with other components
When combined with materials such as PVA and cellulose, glycerol further enhances flexibility by optimizing the arrangement of molecular chains. For example, in nanocellulose starch composite materials, the synergistic effect of glycerol and PVA can promote chain sliding, resulting in a fracture elongation of 41.92%. In addition, glycerol can improve surface smoothness, reduce porosity, and enhance the overall processability of materials