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Polymer Rheology

Polymers have a wide range of flow properties. These properties vary not only by polymer type, but by manufacturer and by batch to batch. It is calmly accepted that polymers vary, and calmly accepted that some control of the variation should be employed. In terms of material characterisation, this leads to two major questions :- 1. What is the rheology of this particular polymer ? and 2. What has changed between batches ?
Polymer rheology covers a number of properties, and each of these plays a prevalent role at different points in a process ( e.g. shear viscosity to determine extruder pressure, extensional viscosity to determine fibre processing) . These properties can vary independently and so it is important to characterise the correct property for a given application. DrRheology offers the measurement of a range of rheological properties. We can also model a process and show the relevant changes that can be expected.

Going about the job of testing.

Testing always can be classified as either 1. We don't know what it is, and we're finding out about it. or 2. We know what it should be, and we're just checking. The first kind of testing requires some time to check on the fundamentals - is the flow stable? is the temperature optimum ? does it degrade? is it repeatable ? is there significant inhomogeneity ? The second kind of test is generally referred to as QC testing, where we simply repeat what we did before.

Testing for processability should generally be done at rates, pressures and temperatures that resemble those found in the process. For this kind of work, we will generally recommend a capillary rheometer or an extruder. For fundamental chemistry, will generally recommend a rotational rheometer. We can supply results as raw data, or as a model. We can also supply calculated and CFD models of the melt in a process.

Testing you can order now

Description/Benefit

Melt Flow

To ISO
Request for MFI / MVR / MFR testing

 

Shear Viscosity

Measured on a lab rotational rheometer
Ideal for chemical modeling
Ideal for viscoelastic measurements
Can do degradation
Request for Shear Viscosity testing

Shear Viscosity

Measured on a lab capillary rheometer (request poster)
Ideal for processing data
Data available in standard models
Degradation measurements available
Melt fracture (flow instability)
Die Swell
Request for Shear Viscosity testing


Wall Slip

Measured using capillary flow
Multiple measurements analysed to give -
- real shear viscosity,
- extensional viscosity,
- wall slip
Request for Wall Slip testing


Die Swell

Measured using capillary flow
Ideal for process measurements
Request for Die Swell testing


Extensional Viscosity

Measured using contraction flow
Necessary data for many processes
Sensitive measurement of polymer and blend structure
Sensitive measurement of degradation
Melt Rupture
Request for Extensional Viscosity testing


Extensional Viscosity

Measured using pulling flow
Ideal for medium strain rates
Request for Extensional Viscosity testing

Analysis of your existing data

We can take your existing data files and :-
Fit data to any standard model
Fit data to shear, extension and slip.
Request for Data Analysis


Calculation of process effect

We can calculate :-
1. The process pressures that will result from the measurements on your material
2. The process changes that will take place as a result of changes to the rheology of the polymer melt
Request for Process Calculations


Rheometer Training

We can train your staff to make a range of measurements and on how to interpret and use the data
.Request for Rheometer Training

Simple Animation Of Polymerisation Variation

Consider the manufacture of a polymer. During the polymerisation process, we inevitably get variation between batches. See the simple animations below which show how variation can take place using the Carreau model.

A Varies n varies r varies

As part of our testing and analysis services, DrRheology can measure your material, fit the data, and present what is changing in your materials.

   
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