Plasticizers commonly used in coatings: epoxy soybean oil (ESO), dibutyl phthalate (DBP), dioctyl phthalate (DOP), etc.
Epoxidized soybean oil, ESO for short, is a light yellow viscous oily liquid at room temperature. Non-toxic. The boiling point is 150°C (0.53 kPa). Soluble in most organic solvents and hydrocarbons, but insoluble in water. It has excellent heat resistance, light resistance and compatibility. It is often used as a plasticizer for PVC products. In addition, it has excellent effects in coating applications.
Plasticizers commonly used in coatings and their functions
The role of plasticizers in coatings is to increase the flexibility of the coating film. For some brittle paint base materials, plasticizers are indispensable in order to obtain coating films with better flexibility and other mechanical properties.
Plasticizers in coatings can generally be divided into two categories. One type is the main plasticizer (solvent plasticizer), and the other is the auxiliary plasticizer (non-solvent plasticizer). The main plasticizer is like the solvent of the base resin, some of their groups can interact with some of the groups in the resin, so the main plasticizer and the resin can be mixed with each other. Because the plasticizer has a small molecule, it can enter the molecular structure of the resin polymer and reduce the rigidity of the resin. However, the addition of the plasticizer will also cause some loss of the mechanical properties of the coating film.
Co-plasticizers have no dissolving effect on the base resin, and they can only be miscible with the base resin when the added amount is not too much. The auxiliary plasticizer has only a physical effect (lubricating effect) on the base resin, so the impact on the mechanical strength of the coating film is not as great as that of the main plasticizer. However, the auxiliary plasticizer is easy to migrate or permeate out of the coating film, which makes the flexibility of the coating film poor.
The addition of plasticizer in the coating has a certain effect on many properties of the coating film, such as tensile strength, toughness, elongation, permeability and adhesion. Depending on the type of base polymer and plasticizer, the impact on these properties is also different. Generally speaking, the addition of plasticizers will increase the extensibility of the coating film and reduce its tensile strength. Within a certain amount of plasticizer added, the permeability of the coating film will remain basically unchanged, but when the added amount of plasticizer continues to increase, the permeability of the coating film will increase sharply. The toughness and adhesion of the coating film first increase with the addition of plasticizer, but after reaching a peak, it gradually decreases. In addition to affecting the mechanical properties of the coating film, the plasticizer will also affect some other properties of the coating film. Therefore, the appropriate amount of plasticizer should be determined after a comprehensive balance based on consideration of various factors.