The selection criteria for dyes used in masterbatch colorant should not only include the related technical standards of the pigments, but should also refer to the interactions between the polymers and additives. The processability and performance demands of the application need to be considered. These factors include things such as heat resistance, migration fastness, weather fastness, and solvent resistance. The dye selected should be brightly colored, fade resistant, and durable. The required performance and evaluation methods of the dyes used for masterbatch are detailed in the sections below.
1. Tinctorial strength
The tinctorial strength of a dye refers to the quantity of dye required to create a product of a specific color. It can be expressed as the percentage of the tinctorial strength of a standard sample. For example, A 1g white dye was added into a 1g standard sample to create a mixture with a certain color. Then take a 1g dye sample which needs to be tested and add some amount of white dye gradually until the color of the mixture becomes the same as the standard sample mixture under a standard light source. The tinctorial strength of the dye is: I=B/A×100% (B is the added amount of white dye). The tinctorial strength of the dye will be affected by the properties of the dye and its dispersion degree. The degree of dispersion of the dye refers to its refinement degree. Usually, the tinctorial strength of dye will enhance as the dispersion degree increases within a certain range of values. However, the tinctorial strength will decrease as the dispersion value exceeds the maximum value. Above is the standard for the tinctorial strength of dye applied to inks and coatings. The selection criteria of the dye for plastic is similar, but resin will be suggested for the adjustment. Changing the white dye of previous methods to resin, the ratio of B and A will be the related tinctorial strength of the dye used for plastic when the color of the standard sample and testing sample is the same. A is the amount of resin for standard palettes. B is the amount of resin for samples which need to be tested.
2. Heat resistance
The level of heat resistance of dyes used for plastics affects the changing of colors and other properties under processing conditions and operating temperatures. The effect of heating time needs to be taken into consideration when testing the heat resistance of the dye because the heating time of the plastic varies with different processing methods and applications. Generally, the heat resisting time of the dye is required to be within 4-10 rain. The higher the temperature, the shorter the heat-resisting time of the dye.