In Pursuit Of The Perfect Injection Moulded Part 8 – Discoloration


Discoloration, or ‘colour streaking’, occurs when a moulded part is a different colour than intended. Often the discoloration is limited to a localised area or a few streaks of abnormal colour on a moulded part. This defect typically affects the appearance of the part without reducing its strength.

Causes of discoloration in moulded products and how to prevent it

In Pursuit Of The Perfect Injection Moulded Part - Discoloration

A common cause of discoloration is leftover pellets in the hopper or residual resin in the nozzle or mould from a previous production run. Poor thermal stability of the colouring agent or improper mixing of the masterbatch are other potential causes. Take the following precautions to limit the risk of discoloration in your injection-moulded products:

  • Ensure that workers properly clean the hopper, nozzle and mould between production runs to eliminate any residual pellets or base material
  • Consider using a purging compound to remove excess colour from the machine
  • Ensure you or your supplier is using a colour agent with adequate thermal stability
  • Ensure that the masterbatch is evenly mixed for consistent colour output

Patterson & Rothwell are a Plastic Injection Moulding Company based in the North West of England, UK producing goods for many business sectors. Our ethos is to offer our customers a professional yet flexible approach and of course provide attention to detail at every stage. Please contact us if you wish to discuss any Plastic Injection Moulding Project.