Rheology

Get control of polymer processing by understanding the rheology!

Rheology is the science that studies the deformation and/or flow behavior of liquids and solids. Polymers in the solid or in the liquid (molten) state that respond  to an external force (stress) by deformation can be measured at the Senbis laboratories. In order to do so we have a range of equipment and methods available. We can advise you about the right equipment and method in order to analyze your materials and elucidate the reological properties.

The rheological properties of polymeric materials are impo...Read more

Get control of polymer processing by understanding the rheology!

Rheology is the science that studies the deformation and/or flow behavior of liquids and solids. Polymers in the solid or in the liquid (molten) state that respond  to an external force (stress) by deformation can be measured at the Senbis laboratories. In order to do so we have a range of equipment and methods available. We can advise you about the right equipment and method in order to analyze your materials and elucidate the reological properties.

The rheological properties of polymeric materials are important to know for a good performing end application and are key for good processing.

Overview of available equipment, analyses and standards

Available equipment Standard Description
Rotational rheometer (Brookfield) User defined e.g. for liquids and slurries
plate-plate (oscillary) rheology Low shear range
Capilary rheology (Göttfert) Intermediate shear range
Extrusion rheology (Haake Polylab) User defined High shear range
Extensional rheology (Göittfert)
Ubbelohde (solution) viscometry PLA, PEF, PBT, PET, PA
Melt flow Index, melt flow rate (ASTM D1238, ASTM D3364, ISO 1133)
Dynamic mechanical analyses (DMA)

Most polymeric materials respond non-Newtonian to external applied stresses, meaning that the apparent viscosity is non-linear with the applied stress: most often the apparent viscosity decreases with increasing stress (a phenomenon called shear thinning) due to the alignment of polymer chains at high shear rates. Moreover, polymeric materials may behave viscoelastic and the deformation can be split up in two parts:

  • Viscous deformation is irreversible (deformation is permanent after removing the external stress). The viscous deformation is accompanied with an energy loss by dissipation of heat. The viscous part of deformation can be quantified by the loss modulus (G’’).
  • Elastic deformation is reversible (material returns to the original state after removing the external stress). The elastic component can be quantified by the storage modulus (G’).

The loss and storage modulus of a material can be measured by applying an oscillatory shear and can be conducted in the solid state as well as in the liquid state (polymer melt).