PEKUTHERM® as a Contamination & Carbon Removal Tool: Black Specks, Buildup & Degraded Polymer
Updated: Sep 2
Tool 2 of 5: Contamination & Carbon Removal
Black specks rarely begin at the machine exit. They usually begin somewhere inside the processing system.
Degraded polymer, old color, burned material and carbonized residue can remain attached to screws, barrels and other internal surfaces long after a production run appears to have changed over successfully. Bernd Krebs President & Chief Executive Officer
Eventually, some of that contamination can break loose and re-enter the melt stream.
The operator sees a black speck. The real problem may be material that has been sitting inside the machine for hours, days or much longer.
That distinction matters because moving resin through a machine is not necessarily the same thing as cleaning the machine.
PEKUTHERM® approaches the problem differently.
Instead of relying on fresh resin, carrier resin, lubrication or a chemical reaction, PEKUTHERM® forms a self-adhering thermoelastic purge that mechanically soft scours internal processing surfaces and carries removed contamination out of the system.
That makes contamination and carbon removal the second major way processors can use PEKUTHERM® as a production tool.
Black Specks Are a Symptom
Seeing black specks in a molded part or extruded product tells a processor that contamination has entered the melt stream.
It does not necessarily tell you where that contamination originated.
Possible sources can include:
degraded polymer
carbonized material
old color residue
burned material
material retained around screw flights
contamination attached to barrel surfaces
residue in nozzles, dies or other processing areas
And not every dark particle should automatically be diagnosed as carbon
The important production question is:
What is remaining inside the equipment that should no longer be there?
Running additional production resin may eventually make the visible contamination disappear. But if material remains attached to an internal metal surface, the processor may only have temporarily stopped seeing the problem.
Production resumes.
Temperature and pressure change.
The machine cycles.
More residue breaks loose.
And the black specks return.
Displacement vs. Cleaning
This is one of the most important distinctions in purging. A resin flush primarily moves material forward. That can be perfectly adequate when the goal is a simple displacement from one compatible material to another.
But material that has degraded and adhered to a screw or barrel presents a different problem.
Additional resin may flow around or over that buildup without removing it completely.
PEKUTHERM® is designed around a physical cleaning mechanism instead.
As PEKUTHERM® reaches its processing condition, it softens into a thermoelastic consistency and conforms to the available internal geometry. The purge self-adheres and forms a soft-scouring plug.
As that plug moves through the equipment, it can:
mechanically scour contaminated processing surfaces
lift degraded polymer from metal
capture carbon buildup and color contamination
carry removed contamination toward the machine exit
clean toward the underlying metal surface
exit without leaving carrier-resin residue behind
There is no chemical reaction required. There is no soaking period required.
And PEKUTHERM® does not depend on diluting a cleaning ingredient into a carrier resin.
Why Carbon and Degraded Polymer Build Up
Plastic processing equipment operates under combinations of heat, pressure, residence time and mechanical shear.
Small amounts of material can remain behind during normal operation.
Over repeated production cycles, trapped or slow-moving polymer may continue to receive heat.
Eventually, that material may:
degrade,
darken,
oxidize or carbonize,
adhere more firmly to processing surfaces, and
later break free into production.
This is why a machine can produce apparently clean material today and still generate contamination later. The contamination did not necessarily appear suddenly. It may have been developing gradually inside the machine. Bernd Krebs President & Chief Executive Officer
That is also why recurring black specks should not always be treated only as a quality-control event.
They can be an indication that the equipment itself needs a deeper cleaning.
PEKUTHERM® Cleans Through Physical Contact
The mechanism is what separates PEKUTHERM® from simple flushing.
PEKUTHERM® is engineered to create a self-adhering thermoelastic plug that conforms to the internal processing path.
Think less about washing something through the machine and more about physically contacting the surfaces that need to be cleaned. The material develops a pencil-eraser-like thermoelastic consistency that allows it to press against contaminated surfaces without abrasive wear. Bernd Krebs President & Chief Executive Officer
That physical contact helps PEKUTHERM® soft scour:
screw flights
screw roots
barrel surfaces
processing channels
other reachable internal metal surfaces
The purge then carries loosened contamination forward as it exits.
This is why PEKUTHERM® is a mechanical purging compound, not a chemical purge.
Its cleaning mechanism is physical. Cleaner metal matters.
For a processor, the objective should not simply be:
“Did the old color disappear?”
A more useful question is:
“What is still attached to the machine?”
Material can look clean at the nozzle or die while hidden contamination remains upstream.
That hidden material can later contribute to:
black specks
color streaks
startup scrap
rejected parts
repeated purging
unplanned cleaning
production interruptions
unnecessary screw pulls
A deeper mechanical cleaning helps address the contamination source rather than only its visible symptoms.
PEKUTHERM® is designed to clean down toward the metal surface while remaining non-abrasive to the screw and barrel.
The Incoming Resin Should Make Product, Not Finish Cleaning the Machine
There is another production cost that can easily be overlooked. After a purge, processors frequently begin feeding the next production resin and watch the output to determine whether the machine is finally clean.
That means valuable incoming resin is being used as a cleanliness test.
If contamination continues appearing, more production resin becomes startup scrap.
PEKUTHERM® provides another advantage: removed contamination remains visible in the purge as it exits.
The purge can therefore help the operator evaluate whether contamination is still being removed before committing large quantities of the incoming production material.
This can be particularly valuable when the next material is expensive, transparent, lightly colored or highly sensitive to contamination.
The goal is simple: Use production resin to make product, not to finish the cleaning process.
Carbon Removal Is Also Preventative Maintenance
Contamination removal should not be limited to the day black specks become unacceptable. Once degraded material has accumulated substantially, cleaning becomes more difficult and production risk increases.
Scheduled mechanical purging can be incorporated into a preventative-maintenance strategy to help remove residue before it becomes a larger problem.
That can be especially useful around:
scheduled shutdowns
startup procedures
difficult material transitions
dark-to-light color changes
high-temperature processing
transparent applications
recurring contamination events
planned maintenance
The objective is not simply to react to contamination. It is to manage buildup before contamination begins controlling the production schedule.
PEKUTHERM®: More Than a Purge
Contamination and carbon removal demonstrates why PEKUTHERM® should be viewed as more than material used during a changeover.
It is a production and maintenance tool.
For contamination control, PEKUTHERM® provides a physical cleaning mechanism designed to:
mechanically soft scour internal surfaces
remove degraded polymers
capture carbon and color contamination
expose cleaner metal surfaces
carry removed contamination out of the machine
help confirm cleanliness before introducing valuable production resin
And it accomplishes that without relying on a chemical reaction, carrier resin or abrasive cleaning action.
Follow the PEKUTHERM® Tool Series
PEKUTHERM® — More Than a Purge. It’s a Tool.
Tool 1: Material & Color Changeovers
https://www.pekutherm.org/post/post-material-color-changeovers-injection-molding-extrusion-pekutherm
Tool 2: Contamination & Carbon Removal
Coming Next: Tool 3 — Preventative Maintenance
Put PEKUTHERM® to Work in Your Machine
Every injection molding and extrusion process has different materials, temperatures, equipment geometry and contamination challenges.
UniTemp can help identify the appropriate PEKUTHERM® formulation based on application type, machine size and processing temperature.
PEKUTHERM® formulations cover processing temperatures from 175°F to 752°F (79°C to 400°C).
Want to see how PEKUTHERM® performs in your own equipment?
Request a sample and put the cleaning mechanism to the test.
UniTemp St. Joseph, Michigan PEKUTHERM® Purging Compounds Made in America
Comments