The quality inspection of pigments can basically be divided into two categories. One is the basic property test of pigments and the other is the application property test. Due to the relatively large number of projects and the relatively wide range of content, we can only extract some of the more practical items from these two categories for discussion based on the specific circumstances of our country.
First, color
(I) Purpose and Definition
The important feature of chromophores is that they are colored. Therefore, the color of pigments is undoubtedly the most important indicator. If there is no color, they will lose their significance.
The vividness of the color will determine the color effect of the final product. If it meets the standards, it will affect the consistency of the product. In addition, color is a very sensitive characteristic index, which is easy to be noticed by people. Therefore, it is very important to control the standard and consistency of the color of the colored body. It must be pointed out that the requirements for color in the ink industry are much higher than in the paint industry, because the quality of color prints is largely determined by the color.
Because different pigments have different colors, and each color has its own unique color characteristics (such as dominant wavelength, brightness and purity, etc.), its content is more extensive, and the method of determination is also more. Only simple and practical standard comparison methods are discussed here.
(B) Appliances and Materials
1. appliance
(1) Toner grinding machine
(2) 1/1000 balance
(3) 2 ml syringe
(4) small withered knife
(5) Scrape (ink) knife (or blade)
(6) Advanced Forest Paper
2. Wood
Dilution oil (viscosity 2500-3000 centipoise/25 °C, acid value <8), close to the size 4 oil specifications.
(c) Methods
Weigh about 0.5 grams of pigment sample on the balance (specific gravity can be weighed about 1 gram or so), place it on a glass plate, and add about 1 ml with a syringe (or burette). About 1/2 ml of ink, mix it thoroughly with a withered knife, then mix the evenly-mixed pigment with the varnish, place it on a toner grinder (usually easy to disperse pigments such as organic yellows for 100 to 200 times , difficult to disperse pigments such as organic red can be ground 200-300 times) into a slurry. Then apply it with a standard sample (have been grinded into a slurry) on Dowling paper and compare the color with a doctor blade.