The use of leveling agents
For a defined formulation system, the appropriate leveling agent species should be selected based on the nature of the formulation and the performance achieved with the desired leveling agent.
1, solvent-based coating system
In the primer and middle lacquer formulations, acrylic leveling agents are commonly used. If deaeration and substrate wetting are required, a medium molecular weight or high molecular weight acrylic leveling agent should be selected. In the primer, if you need a stronger substrate wetting, you can choose to significantly reduce the surface tension of the silicone leveling agent and modified acrylic leveling agent (such as fluorine modified acrylic leveling agent and phosphate ester Acrylic acid leveling agent), if the silicone leveling agent and fluorine modified acrylic leveling agent appears stable foam, the impact of interlayer adhesion and other side effects, should be used phosphate modified acrylic leveling agent.
In the topcoat and transparent paint formulations, the appearance of the paint film is relatively high, generally choose low molecular weight acrylic leveling agent, which will get a good leveling, the film is not easy to produce fog. In the cross-linked curing system, the use of reactive functional groups containing acrylic leveling agent often get better leveling, while improving the physical and chemical properties of the film. Silicone leveling agents are necessary if the film is required to have better fluidity or requires slippage and scratch resistance, and in this case it is preferred that the silicone leveling agent be used in combination with the acrylic leveling agent.
It should be noted that, in the vertical surface construction, the silicone leveling agent to provide leveling performance at the same time, can effectively reduce the coating sagging tendency. In addition, in the metal flash paint formulations, should be used with caution silicone flow leveling agent, because it may lead to uneven arrangement of sheet aluminum pigment paint uneven color.
2, powder coating system
The leveling process of powder coatings is divided into two stages. The first stage is the melting of the powder particles, the second stage of the powder particles melt into a smooth film. Powder coating does not contain solvent, in the film forming process does not produce surface tension gradient, leveling is more related to the substrate wetting.
Powder coatings often use acrylic leveling agent. If the leveling agent is liquid, it is generally necessary to preform the masterbatch to use it. There are also powder made of acrylic leveling agent, specifically for powder coatings, these products are liquid acrylic leveling agent adsorbed on the silica powder, some low leveling agent with calcium carbonate adsorption.
If the powder coating requires smoothness and resistance to injury, it is necessary to use silicone leveling agent, has been made of powder specifically for the powder coating of silicone leveling agent. Use silicone flow leveling agent to avoid the formation of shrinkage.
3, water-based paint system
Water-based coating system is divided into water-soluble system and latex system.
In water-soluble systems, the surface tension of the system is strongly reduced. The most commonly used silicone leveling agents and fluorocarbon leveling agents are the same as those used in solvent-borne coatings. Of course, if a truly flat surface is needed, the acrylic leveling agent for the aqueous system is required.
For the latex system, the film formation mechanism is completely different, the viscosity does not change with the solvent evaporation. The use of leveling agent in the formula may improve the substrate wetting of the coating, acrylic leveling agent can improve the film flatness, but the main flow performance of the coating, more by adding rheology control agent to control and adjust The.