Material
Masterbatch
Answer in brief
Masterbatch is dosed at a few percent, which means a small error in the feeder is a large error in the product.
Colour deviation and additive underdosing both show up in the finished part, and overdosing simply burns money.
- Use gravimetric dosing and verify it against consumption.
- Plan changeover, because colour carryover is the usual complaint.
- Convey gently, since granules abrade and dust affects dosing.
Reviewed October 21, 2026 · Updated November 10, 2026
Handling challenges
Masterbatch is a small stream with a large effect, so the engineering attention goes to accuracy and changeover rather than to capacity.
Dosing accuracy
At two percent addition, a five percent feeder error is a ten percent colour deviation in the part.
- Gravimetric feeders with regular calibration rather than volumetric screws.
- Stable inlet conditions, since a surging refill upsets the weigh signal.
- Consumption reconciliation per batch as an independent check.
Changeover and carryover
Residual pigment in hoppers, hoses and feeders appears in the next product, and dark colours are visible at very low concentrations.
Quick-release hoppers, smooth internals and a defined purge procedure make a colour change a planned step rather than a gamble.
Conveying
Granules abrade in high velocity lines, and the resulting dust changes both dosing behavior and part appearance.
Short, low velocity vacuum conveying from the container directly to the feeder is usually the cleanest arrangement.
Drying
Carriers based on hygroscopic polymers need drying like the base resin, and a wet masterbatch produces the same defects as wet resin.
What to establish before buying equipment
- Addition rate range and the accuracy the product demands.
- Number of colour changes per shift.
- Granule size and bulk density per product.
- Whether the carrier requires drying.
Storage and conditioning
Masterbatch is a pigment or additive carrier, and the critical property is that it stays what it says it is.
Granules flow well and store without drama. The real risk is cross-contamination: a few granules of the wrong colour in a clear product is a batch loss, and they are invisible in a silo.
- Dedicate or thoroughly clean every path between colours.
- Keep it dry; some carriers and additives are moisture sensitive and cause defects later.
- Label and track at every transfer; the material cannot be identified by eye once it is in the system.
What this means for equipment
Cleanability and dosing accuracy define the equipment.
Masterbatch is added in small proportions, so the dosing device decides the product colour and the dosing error is directly visible. Gravimetric feeding is the norm where the proportion matters.
- Gravimetric dosing with a short, cleanable path to the process.
- Quick-release geometry for colour changes; cleaning time is production time.
- Conductive components where static would hold granules in the line.
Safety and regulatory
Polymer dust is combustible and the additives decide the rest.
- Explosion protection where fines accumulate, especially in dust collection.
- Safety data for the specific additive package, not for the polymer alone.
- Dust capture at dosing points, where fines from granule abrasion appear.
Material behavior
- Flowability
- Free flowing granules
- Abrasiveness
- Low to moderate
- Cohesiveness
- Low
- Moisture behavior
- Some carriers are hygroscopic and need drying
- Contamination risk
- Colour and additive carryover between products
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Frequently asked questions
Why is cross-contamination the main risk?
Because a few wrong granules ruin a batch and cannot be seen in a silo or a hopper. Dedicated or properly cleaned paths are the only control.
Why gravimetric dosing?
Because masterbatch is added in small proportions and the error is directly visible in the product. A volumetric device drifts with granule size and bulk density.
Does masterbatch need explosion protection?
Where fines accumulate, yes. Granules themselves are not the problem; the abrasion dust that collects in the filter is.
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