# Capillary rheometry and wall slip in WPC

Canonical: https://woodplasticcomposite.net/guides/capillary-rheometry-and-wall-slip-in-wpc/
Language: en
Updated: 2026-10-15
Version: 1
Review: AI-assisted English editorial draft. Human technical review has not been recorded.

## Summary

A filled composite's flow measurement can depend on its interaction with the measuring wall. Rheological interpretation should consider the apparatus and corrections rather than treating every apparent viscosity as intrinsic.

## Technical context

Laboratory and production flow conditions may differ. Slip, pressure effects and specimen history can complicate a direct transfer from one measurement to another. Research comparing laboratory and on-line methods highlights the need for suitable process data.

https://woodplasticcomposite.net/guides/capillary-rheometry-and-wall-slip-in-wpc/#technical-context

## What to measure and document

Specify the instrument geometry and operating conditions. Use a method appropriate to the material and investigate relevant corrections with a rheology specialist. Compare predictions against actual processing observations rather than relying only on a smooth fitted curve.

https://woodplasticcomposite.net/guides/capillary-rheometry-and-wall-slip-in-wpc/#verification-plan

## Implications for development and specification

For process development, document where the data are valid. A rheology model calibrated under one set of conditions is not automatically reliable for another die or formulation. Product performance still requires separate verification.

https://woodplasticcomposite.net/guides/capillary-rheometry-and-wall-slip-in-wpc/#practical-decision

## Related reading and evidence limits

A research comparison of laboratory and on-line WPC flow measurements. Use the linked work as related reading. The practical checks above are editorial recommendations, not reported test results or a substitute for product qualification.

https://woodplasticcomposite.net/guides/capillary-rheometry-and-wall-slip-in-wpc/#reading-scope

## Key points

Laboratory and production flow conditions may differ.
Specify the instrument geometry and operating conditions.
For process development, document where the data are valid.

## Comparison

Review step | Evidence to retain
Material and geometry | Exact specimen or product identity
Verification | Method, conditions and individual observations
Decision | Approved scope and documented limitations

## What evidence is needed for capillary rheometry and wall slip in WPC?

Specify the instrument geometry and operating conditions. Use a method appropriate to the material and investigate relevant corrections with a rheology specialist. Compare predictions against actual processing observations rather than relying only on a smooth fitted curve.

## Sources

1. Rheology for WPC extrusion: laboratory vs on-line rheometry — https://doi.org/10.3390/polym17202782