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How are plastics colored?

Coloring plastics involves creating colors that are pleasing, meet color card deviation requirements, are economical, and do not change color during processing and use, based on the three primary colors of red, yellow, and blue. Additionally, coloring can be used to meet specific application requirements.

Coloring is a comprehensive consideration based on factors such as plastic properties, molding processes, pigment characteristics, color combining principles, and product requirements. It involves combining various pigments to achieve the desired color.

In color adjustment, mastering the techniques of adjusting brightness, hue, and color deviation is essential.

The principle of color adjustment is to adjust brightness before adjusting hue because changing brightness will inevitably affect hue.

Adjusting Brightness:

Based on the target sample, observe and analyze its transparency and brightness levels. Determine the proportion of black and white components in the mixture and determine the concentration of colored pigments or the proportion of fluorescent pigments in colored colors. The coloring power of pigments can be confirmed through trial plates using various pigments on the same plastic substrate. Additionally, understand the variation in hue and concentration when adding a certain proportion of titanium dioxide to each colored pigment.

During the color adjustment process, when moving towards darker shades, distinguish whether the hue is dark or black based on the color light. To adjust the hue, only additional colored pigments should be added, while black pigments can be added to achieve darker shades.

When moving towards lighter shades, determine the amount of titanium dioxide needed based on the desired color intensity. If the color is not intense enough, more titanium dioxide can be added. Other color pigments should also be added proportionally. Finally, estimate the proportion of colored pigments based on the darkness or lightness of the hue and the coloring power of various colored dyes.

Adjusting Hue:

In theory, most colors can be achieved using the three primary colors of red, yellow, and blue. However, in practice, the colors of various dyes are not pure colors but lie between pure colors, containing color light from adjacent colors. For example, red pigments could have yellowish-red and bluish-red variations, blue pigments could have reddish-blue and greenish-blue variations, and yellow pigments could have greenish-yellow and reddish-yellow variations.

During color adjustment, attention should be paid to the complementary nature of color light. For example, when adjusting a bright green color, phthalocyanine green can be used directly. However, when adjusting a darker shade of green, combinations of greenish-blue and greenish-yellow should be used, instead of complementary combinations of reddish-blue and greenish-yellow.

Adjusting Color Deviation:

After estimating brightness and hue, a basic formula can be determined. After trial plates are made and compared to the standard sample, color deviation can be corrected. Color deviation is related to brightness, color intensity, luminosity, and hue bias.

Firstly, determine the aspect of color deviation. Adjust black and white pigments for brightness, and adjust the amount of other color pigments or add fluorescent pigments and whitening agents to adjust color intensity and brightness. Hue bias can be adjusted by increasing or decreasing the proportion of specific color pigments or using complementary relationships.

However, note that the use of complementary colors should be approached with caution as it may darken the color.

Determining the Color Adjustment Formula:

First, determine the amount of titanium dioxide. This is a crucial technical step because a slight change in the amount of titanium dioxide will greatly affect the color, leading to corresponding changes in the amount of other pigments.

Analyze the color range of the color sample and identify the main and secondary colors and their proportions. Choose pigments that closely match the color light of the sample. For example, when adjusting red tones, select a bright red pigment if the sample leans towards yellow, or select a bright red or fluorescent red if it is vibrant. Finally, consider whether to add fluorescent pigments or whitening agents based on the color intensity of the sample.

Min-Hui’s two-color machine can be well used in colored products.

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