In order to make plastic even coloring, two conditions must be met: the pigment particles well refined; uniformly dispersed in plastic (mixed). Pigment dispersion not only affects the appearance of the colored products (spots, streaks, luster, color and transparency) and processability, but also directly affect the quality of coloring products, such as strength, elongation, aging resistance and resistivity.
How much pigment dispersed particle size is appropriate, the following data is available to 30um, product surface spots, streaks instructions, pigment particle size greater than; diameter 10 ~ 30um, products Matte; when particle size less than 5um, for general products, used to meet, but with demanding product requires the pigment particle size should be less than 1um. Thus, the colorant in plastics dispersion is good or bad is an important part of a successful coloring.
Pigment in plastics dispersion process can be divided into three steps; wetting, thinning, mixing and dispersing, the first step is to use a wet pigment dispersing agent, so that the cohesion of the pigment is reduced, reducing the novel to the screen surface energy, so that when further processing, and will not produce another agglomeration. The second step is to refine, is the pigment agglomerates or aggregates crushed to particle size to minimize process. It mainly relies on free movement (impact stress) between the pigment particles and pigment aggregates is done by stress (shear stress) of the surrounding medium. The third step is mixed and dispersed, mainly through the introduction of mechanical energy to overcome the cohesion between the pigment aggregates in body chemistry and physical force, to achieve uniform dispersion purposes.
Poor dispersion can cause products to produce the following shortcomings: unstable coloring strength; bad color; blotches, streaks; surface roughness, caused by uneven printing problem; the more severe the extruder can filter sum game, thin film products, silk products off the network.
