Uneven color/color difference appearing in random copolymer polypropylene injection molded products (variant: strengthened measures)

Areas of varying color depth appear on the product surface, or there is 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. Especially, additional attention is needed on top of the original basis; this problem is more prominent and requires focused attention.

(1) Color masterbatch is unevenly dispersed, with insufficient mixing time or unstable mixing ratio (2) Barrel temperature fluctuates greatly; color masterbatch has different coloring effects at different temperatures (3) Improper screw speed and back pressure settings; plasticizing and mixing are insufficient (4) The barrel or screw is worn; stagnation zones produce discoloration or uneven coloring (5) Mold surface conditions vary; gloss differences in different areas cause visual color difference (6) On top of the original basis, additional attention is needed as process parameter fluctuations or equipment condition changes aggravate this problem

(1) Ensure color masterbatch is fully mixed with the raw material, with mixing time of 5-10min, using weighing equipment for precise metering (2) Stabilize barrel temperature, with temperature difference of each section controlled within ±3°C (190-260°C range) (3) Appropriately increase back pressure to 5-10MPa and optimize screw speed to ensure uniform plasticizing and mixing (4) Check screw and barrel wear, and replace the screw head or check ring if necessary (5) Regularly clean mold cavities to ensure consistent surface condition of all cavities (6) And strengthen process monitoring; on top of the original basis, additional attention is needed to pay special attention to parameter stability

Color difference is caused by uneven colorant dispersion or process parameter fluctuations and needs to be ensured from three aspects: mixing, plasticizing and temperature control. In different production scenarios, targeted preventive measures need to be taken.