Fundamentals of Rhelogy

THE FUNDAMENTALS OF

RHEOLOGY 

  Rheological tests can be very helpful tools for polymer processing and development. This presentation is designed to be an informative introduction and guide to rheological tests, and finding correlations between equipment and processing techniques.

CAPILLARY RHEOLOGY “the flow and shear properties of materials up to high pressures”  pressures”  •

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Provides more information than melt flow testing •

How does the material behave when melted?

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What are the correlations between flow parameters and mechanical properties?

Polymers are non-Newtonian materials, consequently their flow is not proportional to the pressure applied

WHY CAPILLARY RHEOLOGY? •

Determine the optimal working parameters for materials processing (injection molding, blow molding, extrusion, etc.)

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Investigate processing issues in a Investigate faster and non-disruptive manner

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Find which materials will work best be st for complex parts or long flow lengths Replicate manufacturing parameters Replicate for design, troubleshooting, and simulations

TYPES OF RHEOMETERS Rotational

ROTATIONAL RHEOMETERS For viscoelastic properties

Extensional

EXTENSIONAL RHEOMETERS For elongational viscosity (high

Capillary

CAPILLARY RHEOMETERS For viscous properties

viscosity materials) Rotary motion

Rotating drum

Capillary action

Plate geometry: most common for thermoplastic melts

Extensional flows: very sensitive to crystallinity & polymer long-chain branching

Capillary flow: Flow through a narrow space. Different piston speeds (shear rates) applied. Viscosity changes tracked relative to shear rates.