Polyurethane (PU) color pastes may precipitate during use and storage, depending on several factors:
1. Composition
Pigment properties: Some pigments are inherently heavy or unstable and tend to precipitate in liquids.
Effect of dispersants: Dispersants are used to keep pigment particles evenly distributed. If the dispersant is not formulated or used in the right amount, precipitation may occur.
2. Formulation and concentration
Concentration: Too high a concentration of color paste may make it difficult for pigment particles to be fully suspended, causing precipitation.
Formulation stability: If the formulation is unstable, it may cause the ingredients to separate or precipitate.
3. Storage conditions
Temperature: High or low temperatures may affect the stability of the color paste and cause precipitation. Storage temperature should be kept within the recommended range.
Agitation: Color pastes that are not stirred for a long time may precipitate. Regular stirring can help maintain uniformity.
4. pH
Acidity and alkalinity: The pH of the color paste has a great impact on its stability. Changes in pH may cause the pigment to precipitate.
5. Use and application
Mixing: If the mixing is not sufficient during use, precipitation may occur. Make sure the color paste is stirred thoroughly.
Dilution: If the color paste is diluted during use, the choice and proportion of the diluent will also affect the occurrence of precipitation.
Measures to prevent and solve precipitation
Regular stirring: Stir the color paste regularly before use and during storage to keep it uniform.
Proper storage: Store the color paste under the recommended temperature and environmental conditions.
Adjust the formula: Adjust the formula of dispersants and other ingredients as needed.
Filtration treatment: If the color paste has precipitated, use an appropriate filter to remove the precipitate and re-stir it evenly.
The above measures can effectively reduce or solve the problem of PU color paste precipitation.
