Carbon build-up is caused by polymer degradation due to thermal stability of polymer and additives, residence time, shear heat, oxygen exposure, incompatible materials, and poor shutdown/startup procedures. It typically forms in the compression and metering zones where temperatures are highest.
Black specks are usually caused by carbon deposits breaking free from the screw, barrel, or dead spots in the machine during processing, at material change-overs or after a machine stoppage.
Most degradation occurs from the middle of the compression zone through the metering section and screw tip assembly where material is molten and exposed to high heat. Degradation buildup in other areas generally points to specific issues; processing, shutdown procedure or machine damage/design.
Standard purging often removes loose material but does not eliminate embedded carbon. Without removing the residue, contamination returns.
It leads to scrap, downtime, repeat purging, longer changeovers, inconsistent product quality, and inconsistent processing conditions.
A purging compound is a material used to clean processing equipment by removing residual polymer, colour, and contamination from screws, barrels, and hot runners.
Aquapurge products are engineered specifically for carbon removal and deep cleaning, not just material displacement.
If production requires an increase in productivity, a reduction in rejects, a more stable processing window or the company requires more profit.
Yes, but only if they are designed for carbon removal. Mechanical and hybrid purge technologies are required for effective decarbonisation.
A mechanical, soft high-fill compound like BBU is best for removing heavy carbon build-up in high-pressure zones. A hybrid chemically active compound like PCP grades are best for shutdown maintenance.
BBU is a polyolefin-based, highly filled mechanical purge compound designed to scrub carbon from high-compression areas of the machine.
PCP is a hybrid purge compound that uses flow dynamics and surfactants to loosen and remove carbon throughout the entire system.
Use BBU for heavy carbon removal on non-complex systems. Use PCP for complex systems and ongoing cleaning and process stability. Using both together delivers a full system reset.
Yes, Aquapurge products are designed to work across a wide range of polymers used in injection moulding, extrusion, and blow moulding.
In most cases, no. Aquapurge is designed to eliminate the need for screw pulls by cleaning in-place.
Other than a manual stripdown, a structured purge process using the correct compound, proper temperatures, and, when needed, soak or decarbonising procedures.
This is used with hybrid purging compounds such as PCP grades. It involves allowing the purge compound to dwell in the machine so surfactants can penetrate and loosen carbon deposits.
Poor shutdowns can lead to material contamination, oxidation and degradation, increasing carbon formation and rejects during restart.
Yes. Excess heat, shear, residence time and poor material compatibility all contribute to degradation.
By implementing consistent purge and shutdown procedures, using the right materials, conditioning these materials correctly and maintaining proper processing conditions.
It is the true cost of cleaning your system, including material, downtime, labour, scrap, and lost opportunity, not just the cost per kilo.
A cheaper material may require more material, more time, more cycles, and more waste, making it more expensive overall.
By cleaning more effectively and deeper in fewer cycles, reducing repeat purging and stabilising production faster allowing standardised settings to work.
Processors often see significant reductions in scrap across the run as a result of faster achievement of first acceptable parts.
A structured trial where you collect data on your current cleaning process. Aquapurge then deep-clean your equipment back to factory delivered standard and then you compare your legacy purge process against Aquapurge’s to measure improvements in cleaning performance, changeover time, scrap reduction, and production stability.
BBU is a high-performance mechanical purging compound designed to remove carbon, degraded polymer, and contamination from screws, barrels, and nozzles. It works by physically scrubbing surfaces where standard purge materials fail.
BBU is an aggressive soft mechanical purge. Instead of just pushing material through, it scrapes carbon deposits off metal surfaces, making it ideal for heavy contamination and long-term build-up.
BBU is best used when:
Carbon contamination is visible (black specks, streaking)
Changeovers are taking too long
Standard purge compounds are no longer effective
You are preparing for a full process reset
BBU is suitable for:
Injection moulding screws and barrels
Extrusion (with limitations)
Blow moulding (with limitations)
Yes. BBU is highly effective at removing both carbon and residual colour, making it ideal for difficult changeovers.
BBU uses a high-fill scrubbing additive (0.5–1.0 mm) that does not melt or compress, allowing it to physically dislodge carbon from the screw and barrel surfaces.
BBU is most effective in:
Compression zone
Metering section
Screw tip and nozzle
It is less effective in the feed zone, where mechanical compression is lower.
When run correctly, BBU clears itself from the screw as it exits the system, reducing residue and making transitions back to production material faster.
Leaving material in the screw can reduce cleaning performance and cause contamination carryover. Full emptying ensures maximum cleaning effectiveness and clean restart.
Typical process:
Empty the machine of the previous material
Add BBU to the hopper
Purge until output runs clean (white/beige)
Increase back pressure and purge again (approx. 5% of total)
Run screw empty completely
Reintroduce production material using 5 starve-feed cycles
Purge till no residue of BBU evident
Empty previous material from equipment
Check you aren’t wanting to purge through gaps smaller than 1.5mm, melt pumps or complex dies
Remove screens and filters
Dose BBU into hopper
Run until output is clean
Empty machine completely
Perform 5 starve-feed cycles with the next material to clear BBU from the feed section
Continue purging until all evidence of BBU is removed
A controlled method of alternating between emptying the screw throat and reintroducing the next material to ensure:
Complete clearing of BBU from the feed section
Yes. BBU is highly effective before screw removal, resulting in the carbon being removed from the screw and barrel, the screw empty, and highlighting areas of excess wear.
At higher temperatures, the carrier can become sticky, reducing its ability to self-empty and clean effectively.
BBU works across many materials, but caution is required with:
High-temperature engineering polymers
Systems with sensitive flow paths
Yes, but for screws ≤18 mm:
Mix 50/50 with a polyolefin carrier
No. BBU should NOT be used:
Through hot runners
Through filter or mixer nozzles
With very small nozzle openings (<2.5 mm)
Because it cleans with a mechanical process, high compression and unrestricted flow paths are required for effective cleaning. Restricted channels less than 1.5mm, and complex flow paths such as spiral dies or melt pumps are not suitable.
Common issues include:
Worn screws or barrels
Incomplete emptying
Large nozzle openings reducing compression
Carbon in feed zone
Cold nozzles compared to barrel temperature
No. BBU is classified as non-hazardous under current regulations.
BBU consists of:
Polyolefin carrier
Non-hazardous organic scrubbing fillers
Yes. Components are GRAS-rated and FDA compliantfor use in food and packaging applications.
Dust inhalation (irritation)
Slipping hazard from pellets
Burns from molten material
BBU works immediately during purging, often achieving visible results immediately on exit.
Removal of black specks and carbon streaking
Faster changeovers
Reduced scrap
More stable metering stroke
Reduced metering time
Less variance from original set-up sheets
The screw geometry in the condition it was delivered
In many cases, yes. BBU is designed to remove carbon in-place, reducing the need for manual cleaning.
Absolutely, because it directly addresses the root problem:
Carbon contamination destroying production performance
Use the Factory Reset Challenge:
Run current process and collect results
Run BBU to reset the screw and barrel to factory delivered condition
Now carry out a BBU change to compare scrap, time, and output
PCP grades are chemical purging compounds designed to remove colour, material residue, and carbon contamination from plastics processing equipment. They are used across injection moulding, extrusion, and blow moulding applications.
Unlike mechanical purges, PCP uses chemical action to penetrate, break down and loosen carbon deposits. This allows them to clean deeper and more effectively, especially in areas that are difficult to reach.
PCP is ideal for:
Colour and material changes
Removing black specks and carbon contamination
Preventative maintenance
Deep cleaning and decarbonisation
PCP is suitable for:
Injection moulding (including hot runners)
Extrusion systems
Blow moulding processes
PCP removes colour and carbon to gain access to the carbon surface, where its stiff carrier removes loose carbon deposits. With capillary action, the waterbased surfactant penetrates the cracks loosening the carbon. PCP also has an additive that causes the carbon to adhere to PCP’s carrier so when the temperatures are reduced (over a weekend), the carrier shrinks and pulls the carbon off the metal surfaces.
Yes. PCP incorporates the ability to simulate turbulent flow, increasing the flow speed at the side walls of a channel therefore improving cleaning efficiency, which reduces downtime and allows faster transition between materials and colours.
In most cases, yes. PCP removes the root cause of black specks by targeting carbon build-up rather than just flushing the system. Depending on the severity, multiple applications or procedures may be required.
By removing contamination, PCP helps:
Reduce scrap
Stabilise processing conditions
Improve product quality
Restore predictable output
Reduce subsequent colour and material changes
The typical process includes:
Emptying the machine of current material
Increasing Back Pressure to maximum
Adding PCP and purging until clean
Removing Back Pressure and carrying out short shots
Running the machine completely empty
Running the next material using 5 starve-feed cycles
Purging until clean
PCP can be used through open mould purging or by mixing with production material moulding parts. The goal is to ensure all flow paths are cleaned and gates are fully purged, this may require increasing tip heats.
In extrusion:
Empty the machine of current material
Remove screens if applicable
Add PCP and run at safe maximum output (check for shear heat and pressure)
Purge until clean
Clear with production material before restart
In blow moulding:
Empty the machine of current material
Remove screens if applicable
Open die gap to maximum
Stop accumulator dosing (Maximum back pressure / zero fill speed)
Purge with PCP until clean
Initiate accumulator until clean
Empty machine completely
Add next production material
Starve-feeding involves alternating material flow to fully clear PCP from the feed section. It ensures no residue remains before restarting production.
A general guideline is approximately 1kg per 100 tonnes of machine size, though this can vary depending on screw size and if the Hot Runner requires cleaning.
Yes. Regular use of PCP helps prevent carbon build-up and reduces the risk of contamination-related issues.
Decarbonisation is a deep cleaning process where PCP loosens carbon deposits, on shutdowns, allowing contamination to be removed on restart.
Yes. PCP can be used before shutdown to leave the machine in a cleaner state and reduce issues during restart.
PCP should be used between 160°C and 290°C for optimal performance.
PCP is not classified as hazardous, but standard safety practices should always be followed, including proper PPE and safe handling of molten materials.
PCP works with a wide range of polymers, including polyolefins, styrenics, engineering plastics, and elastomers.
Store PCP in a dry environment, in sealed packaging. Open bags should be resealed to prevent contamination and moisture escape.
You should measure:
Reduction in changeover time
Decrease in scrap rates
Improved cleanliness
Increased production stability
Increased flexibility of staff and machines
PCP may have a higher cost per kilo, but delivers a lower total cost per purge due to less required, reduced downtime, faster cleaning, and less waste.
Price per purge looks at the full cost of cleaning, including downtime, improved opportunity cost, flexibility and reduced scrap, rather than just material cost. PCP is designed to win on this metric.
The best way is to run a controlled comparison.
Use PCP in your process and compare it directly against your current method.
Start with the Factory Reset Challenge to see the results in your own operation.
