One of the biggest contributors of scrap in the injection molding and extrusion business is degradation. Raw material that cannot stand up to time and temperature.
Many molders ignore the risks of degradation because they are running resins that are not considered temperature sensitive. They allow material to sit in the injection unit or extruder for extended periods of time because “it’s just polypro.” While it is true that polypro is not very heat sensitive at normal production temperatures, your colorant is.
Many of the pigments used to get the colors we want cannot stand the test of time and temperature. They may be stable at normal processing temperatures, but when they reside in the barrel too long they begin to degrade. This degradation shows up in plastic as black specs. Carbon is produced when the pigments breakdown due to overexposure to heat. You will see the black specs immediately upon startup. They will diminish during the run, but your operators are really good at seeing them aren’t they?The best solution to this type of problem is a preventative measure. Do not leave colored material sitting idle in the machine. Purge out the colored resin with a non-heat sensitive, natural resin or a good commercial purge that is designed to bridge the gap while the machine is sitting idle. It is much easier, and cheaper, to prevent the degradation that results in rejected parts, than it is to try and clean your system after you have degraded it and thrown away a lot of parts.
Ready to get proactive about fixing your color and carbon contamination?