Application
Powder Blending in Plastics Compounding
Answer in brief
Dry blending and separate feeding solve the same problem in different places.
A PVC dry blend absorbs additives into the resin before extrusion; separate gravimetric feeding keeps flexibility for recipe changes.
- Blend where the additive has to be absorbed, feed where the recipe changes often.
- Watch the temperature; mixing generates heat.
- Screen before the extruder either way.
Reviewed October 21, 2026 · Updated October 21, 2026
The problem
Additives have to be distributed evenly and, for PVC, absorbed into the porous resin, which a feeder alone does not achieve.
High speed mixing also heats the material, which matters for temperature sensitive polymers.
Desired outcome
A blend in which every additive is distributed and, where required, absorbed, delivered to the extruder without separation or degradation.
Process approach
High speed mixers heat and blend PVC dry blends, followed by a cooling mixer so the material does not agglomerate in storage.
Where recipes change often, separate gravimetric feeding avoids holding many pre-blends and allows changes without a blending step.
Screening before the extruder catches agglomerates from either route.
- Temperature profile controlled during and after mixing.
- Decision between pre-blend and separate feeding based on recipe variety.
- Screening ahead of the extruder.
Selection factors
- Whether additives must be absorbed or only distributed.
- Number of recipes and the changeover frequency.
- Temperature sensitivity of the polymer and additives.
- Storage time of the blend before extrusion.
- Dust exposure limits for the additives.
Common failure modes
- Blend agglomerating in storage because it was not cooled
- Additive distributed but not absorbed into the resin
- Pre-blending chosen for a plant that changes recipes daily
- Agglomerates reaching the extruder unscreened
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