Analysis and Solutions of Color Streaks, Color Lines and Color Mottles in Injection-molded Products

Analysis and Solutions of Color Streaks, Color Lines and Color Mottles in Injection-molded Products 

The occurrence of this kind of defect is mainly a common problem in plastic parts colored with master batch. Although master batch coloring is superior to dry powder coloring and dye paste coloring in terms of color pattern stability, color purity and color migration, its distributivity, that is, the degree of uniform mixing of the color particles in the diluted plastic, is relatively poor. Naturally, the finished products will have regional color differences. The main solutions are as follows: 

(1) Increase the temperature of the feeding section, especially the temperature at the rear end of the feeding section, so that it is close to or slightly higher than the temperature of the melting section. This enables the master batch to melt as quickly as possible when it enters the melting section, promotes uniform mixing with the diluent, and increases the opportunities for liquid mixing. 

(2) Under the condition of a certain screw rotation speed, increase the back pressure to improve the temperature of the molten material in the barrel and the shearing effect. 

(3) Modify the mold, especially the gating system. For example, if the gate is too wide, when the molten material passes through it, the turbulent flow effect is poor and the temperature rise is not high. As a result, it is not uniform. If the color streaks enter the mold cavity, the gate should be narrowed.