Uneven Color/Color Difference Appearing on Block Copolymer Polypropylene Injection Molded Products (Variant: Strengthened Measures)

Areas of different color shades appear on the product surface, or there is a color difference from the standard color sample. Color difference may appear between different parts of the product, different cavities, or different batches, affecting product appearance consistency. In particular, extra attention is needed on the original basis; this problem is more prominent and requires key attention.

（1）The color masterbatch is unevenly dispersed, the mixing time is insufficient, or the mixing ratio is unstable （2）The barrel temperature fluctuates greatly, and the coloring effect of the color masterbatch is different at different temperatures （3）The screw rotation speed and back pressure are set improperly, and the plasticization and mixing are insufficient （4）The barrel or screw is worn, and the material retention areas produce discoloration or uneven coloring （5）The mold surface conditions are inconsistent, and the gloss differences in different areas cause visual color difference （6）On the original basis, extra attention is needed: process parameter fluctuations or equipment status changes have aggravated this problem

（1）Ensure the color masterbatch is fully mixed with the raw material, with a mixing time of 5-10min, and use weighing equipment for accurate metering （2）Stabilize the barrel temperature, with the temperature difference of each section controlled within ±3°C (200-270 range) （3）Appropriately increase the back pressure to 5-10MPa and optimize the screw rotation speed to ensure uniform plasticization and mixing （4）Check the wear of the screw and barrel, and replace the screw head or check ring when necessary （5）Regularly clean the mold cavity to ensure consistent surface conditions of all cavities （6）And strengthen process monitoring; on the original basis, extra attention is needed, with special attention to parameter stability

Color difference is caused by uneven dispersion of the colorant or fluctuations in process parameters, and consistency needs to be ensured from three aspects: mixing, plasticization, and temperature control. Targeted preventive measures need to be taken in different production scenarios.