How do I remove volatiles in twin screw compounding?

Volatiles are the gases and low molecular weight compounds released as polymer is heated and mixed. Residual monomers, solvents, additives breaking down, trapped air. Leave them in a compound and you get odour, porosity, surface defects and inconsistent performance.

In twin screw compounding, volatiles are taken out at vent ports, usually under vacuum. The screw configuration opens up the melt at the vent zone so gas can escape, and the vacuum pulls it away. It is called devolatilisation, and how well it works depends heavily on how much vacuum you can apply.

Here is the problem. The harder you pull, the more likely melt is to rise up the vent. Compounders often run filled barrels at high throughput, which makes it worse. So vacuum gets backed off and volatiles stay in.

Screwtech Engineering vent port stuffers let you have both. The self-wiping twin-screw design conveys rising melt back down while gas carries on out. Precision tolerances mean full vacuum can be drawn, so volatiles are properly removed.

Screwtech stuffers are a proven design used by many leading compounding and profiling extrusion companies. They are built from high quality stainless steel, with an easy clean two-part vacuum chamber, separate seal housing and an oil filled gearbox with water cooled jacket.

Run at higher fill levels, keep the vacuum on and keep quality up. Screwtech supplies stuffers in various sizes for twin-screw and single-screw extruders. Get in touch to discuss your compounding line.

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