Pigments are indispensable materials in the fields of painting, inks, plastic products, coatings, and more. They give color and beauty to products. However, the color retention ability of pigments is crucial to product quality, especially when faced with acid-base environments. This article will explore in depth the alkali resistance of pigments and how to ensure the high quality and durability of pigments through alkali resistance testing.
1. Alkali resistance of pigments
Alkali resistance is an important performance indicator of pigments, which measures the resistance of pigments to alkaline environments. Alkaline environments usually refer to liquids containing alkaline compounds such as sodium hydroxide, which may cause staining or discoloration of pigments. Alkali resistance of pigments is their ability to maintain color under these conditions without damage.
2. The alkali resistance of pigments is manifested in two aspects:
Staining level: refers to the degree of staining of the pigment in alkaline liquids. A higher staining level indicates that the pigment has better resistance to alkaline environments and maintains color longer.
Color-changing series: refers to the degree of color change of a pigment in an alkaline liquid. Low color-changing series indicates that the color of the pigment lasts longer.
3. The importance of alkali tolerance
The alkali resistance of pigments is very important in various fields.
Painting: Artists use pigments to create paintings that may be exposed to different environments for long periods of time. Pigments with high alkali tolerance ensure that the color of the painting does not fade over time.
Ink: In the printing industry, the alkali resistance of ink is crucial to the color stability of printed matter. Prints need to be displayed in different environments and need to maintain color consistency.
Plastic products: Pigments are widely used in the manufacture of plastic products, such as plastic containers, toys, and household items. These products may come into contact with detergents containing alkaline compounds, and alkaline-resistant pigments can ensure that the color of the products is not damaged.
Coatings: Coatings are commonly used in construction, automotive, and furniture manufacturing. In outdoor environments, these coatings may be eroded by rain and alkaline substances in the atmosphere, so high alkali resistance is required.
4. Pigment alkali resistance test
To ensure the high quality and alkali resistance of pigments, an alkali resistance test is necessary. Here are the general test steps:
Preparation of test solution and filter cake: First, two samples need to be prepared. Each sample weighs 0.5 grams, one of which is added with 20 ml of distilled water and the other with 20 ml of 2% sodium hydroxide solution. The two samples are mixed in a test tube and then shaken.
Filter the test solution: After shaking, filter the test solution to obtain a clear filtrate. If there are particles or turbidity in the test solution, filter paper or other filtration methods are required to obtain a clear filtrate.
Evaluation of staining and discoloration order: The prepared 2% sodium hydroxide solution and filtrate were injected into a cuvette respectively. Then, the alkali resistance of the pigment was evaluated using a standard sample card according to the degree of staining of the filtrate and the degree of discoloration of the filter cake.
Parallel testing: To ensure the accuracy of the test results, parallel testing is usually performed to ensure that the series are the same.
5. Display of results
The alkali resistance of a pigment is usually expressed by the staining level of the filtrate, the discoloration level of the filter cake, or both. These levels are usually expressed on a scale of 1 to 5, with 1 being the worst and 5 being the best. The staining level indicates the degree of staining of the pigment in alkaline liquids, while the discoloration level indicates the degree of color change of the pigment in alkaline liquids.
6. Reference standards
The alkali resistance test needs to follow the national standard GB 5211.7-85 "Pigment alkali resistance determination method".
7. Conclusion
The alkali resistance of pigments is a key factor in ensuring the long-lasting and stable color of a product. By conducting alkali resistance tests, the ability of pigments to resist alkaline environments can be evaluated. This helps manufacturers to select high-quality pigments, ensuring that products can maintain vibrant colors under different environmental conditions. In various fields, such as painting, printing, manufacturing and construction, alkali resistance tests of pigments are an indispensable part of guaranteeing product quality.
