The plasticization process of plasticizers in plastics can be regarded as a process in which resin and plasticizer low-molecular compounds dissolve each other, but plasticizers are different from general solvents. Solvents will volatilize during processing, while plasticizers are It is required to stay in the polymer for a long time and do not chemically react with the resin, forming a solid with the resin. After the plasticizer is added, it can increase the flexibility, flexibility, cold resistance, and elongation of the plastic. Reduce the plastic's hardness, modulus, glass transition temperature, melting point, softening temperature, or low temperature, so that the viscosity of the plastic becomes smaller and the fluidity increases, thereby improving the processing performance.
The mechanism of action of plasticizers is generally considered to be as follows:
1. The van der Waals force of the action mechanism of the plasticizer:
Van der Waals force is a weak gravitational force between molecules in the aggregate state of matter. But this kind of force plays a leading role in the morphology and crystallinity of the polymer. Van der Waals force includes dispersion force, induced force, and orientation force.
2. The dispersive force of the action mechanism of the plasticizer:
The dispersive force exists between all polar or non-polar molecules. It is a kind of gravitational force generated by the interaction of tiny instantaneous dipoles, which makes the adjacent dipoles in a state of being adjacent to each other. But only in non-polar systems, such as benzene, polyethylene, or polystyrene, the dispersion power is the main component.
3. The inducing force of the action mechanism of the plasticizer:
When a molecule with a fixed dipole induces an induced dipole in an adjacent non-polar molecule, the gravitational force between the induced dipole and the inherent dipole is called the induced force. Aromatic compounds have a particularly strong influence because π electrons can be highly polarized. For example, between low-molecular-weight esters and polystyrene or between benzene and polyvinyl acetate, it is mainly induced.
4. The orientation force of the action mechanism of the plasticizer:
When polar molecules are close to each other, due to the orientation of the inherent dipole, a kind of force between the molecules is called orientation force. For example, the interaction of ester plasticizers with PVC or with nitrocellulose is a representative example.
In addition, Orillia Chemicals has discovered through practice that the molecular structure of the polymer in the action mechanism of the plasticizer also affects the attraction between the polymer molecular chains, especially the properties of the groups on the polymer molecular chain, which have strong polar groups. The force between the molecular chains of the group is large, and the force between the molecular chains with non-polar groups is small. In order to make the polymer with strong polar groups easy to shape, plasticizers and plasticizers can be added. The groups will interact with the polar groups of the polymer, thereby weakening the attraction between the polymers, and achieving the purpose of plasticization.
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