Light fastness and weather resistance
The light fastness and weather fastness of pigments are important indicators to measure the application performance. Especially in the case that the standards for exterior wall latex paint have not set indicators such as fading control, understand the light resistance and weather resistance of the pigment, and choose a pigment with good light resistance and weather resistance. After dilution, these two properties change little. important.
The main factors that determine the light resistance and weather resistance of pigments are the chemical composition and structure , and are also related to the surrounding medium and the particle size of the pigments. Generally speaking, the light resistance and weather resistance of inorganic pigments are better than organic pigments, but they are not very good. Inorganic pigments will become darker and darker under the action of sunlight and atmosphere, while most organic pigments will fade.
The lightfastness of pigments can be measured according to GB/T1710-79 "Determination of Pigment Lightfastness". Compared with the degree of discoloration of the blue standard card, it can be evaluated in 8 grades, and the lightfastness of grade 8 is better.
The weather resistance of pigments can be measured by natural exposure or artificial aging instrument aging, which is , and the weather resistance of grade 5 is better.
Acid and alkali resistance
The base layer of architectural latex paint is generally cement mortar and mixed mortar plastering layer, which is alkaline, so the pigments used need to be alkali-resistant.
The use environment of architectural latex paint usually has no acid, so there is no requirement for acid resistance. However, due to the pollution of the environment, acid rain may fall in some places, such as the southwest of my country, so acid resistance requirements are put forward. Of course, acid rain is a weak acid, its pH<5.6, the average pH of acid rain in the world is about 4.2
