Understanding the Color Matching Process of Plastic Packaging 01: Colorant
The color matching is based on three primary colors of red, yellow and blue. The colorants commonly used by engineers can be divided into two types: pigments and dyes.
Pigments can not be dissolved in ordinary solvents, therefore, it is necessary to evenly disperse the pigments in the plastic by means of mechanical heating and stirring, to obtain the ideal coloring performance. According to the structure of pigments, it can be classified into organic pigments and inorganic pigments.
Inorganic pigments, included titanium dioxide and carbon black, have many advantages, such as good thermal stability, great weather resistance, excellent light stability, lower price and superior dispersion performance.
Titanium dioxide is an important white pigment, which can lighten the color of plastics. In the rubber industry,titanium dioxide is also used as a filler for white rubber, by covering the transmittance of resin and increasing its whiteness. Moreover, titanium dioxide can also effectively prevent microbial growth by photocatalysis.
Furthermore, the nacreous pigments can be made by coating mica wafer with titanium dioxide. The excellent chemical corrosion resistance and high temperature resistance make pearlitic pigments suitable for almost all thermoplastic and thermosetting plastics, and they will not make plastic products fading or ashing. Also they provide a brand new color system for plastic packaging, by producing bright metallic luster andpearlescenteffect. According to the different hue, the pearlescent pigments can be divided into three types, silver-white pearlescent pigments, colored pearlescent pigments, rainbow pearlescent pigments.
Carbon black is a frequently-used black pigment, which has UV protection (anti-aging) effect on plastics.Because of its high light absorption, carbon black can effectively prevent the photooxidation degradation of plastics caused by sunlight.Different production processes can obtain various carbon blacks with a wide range of particle sizes and all of them has different properties. According to its tinctorial power, carbon black can be divided into high pigment carbon black, medium pigment carbon black and low pigment carbon black. Carbon black particles are prone to agglomeration, therefore, engineers usually add the dispersant into carbon black for the pre treatment, toimprove the coloring power of carbon black.
Although the heat resistance, weather resistance, hiding power of organic pigments are not as good as inorganic pigments, the coloring intensity of organic pigments is very high. It also has complete chromatography and bright color effect. Therefore, it can use smaller addition quantity to get the same color effect.
As the organic compounds, dyes can be used in most solvents and dyed plastics. It also has high coloring power and good transparency characteristics.While its price is more expensive than inorganic pigments.