Polymer & Co.
Rheometry
What is RHEOmetry ?
Rheometry is a very interesting way to characterize polymers. It is widely used in industry to have an idea on the flow properties of their products.
This kind of analysis allows us to quantify the elastic and viscous behavior of our samples. For that, we use two moduli: storage modulus (G’) and loss modulus (G’’). They are specific of the rigidity (the solid behaviour, G’) and the flow (the liquid behaviour, G’’).
Figure 1 : Rheometry lab equipment
How does it work ?
Rheology measurement consists of putting the sample between two parallel plates with the top plate free to move under an applied force and the bottom plate held fixed. The top plate can have different geometry (parallel, cone) allowing different kind of tests. [1]
First, for our measure, we have done a strain sweep from 0.1% to 200% of strain, to know where the sample has a linear viscosity response. This is linked to the Newtonian behaviour of the sample, and this linear viscosity range is the interesting part for oscillating tests.
For the oscillating tests, we fixed the strain at a percentage comprised in the linear viscosity range, and we apply an oscillation with the top plate. The resulting strain (or stress) can be resolved. So we determined a complex modulus (G*) which is a function of frequency :
G* = G’ + iG’’
where G’ (storage modulus) and G’’ (loss modulus) give information on energy storage and energy dissipation in the flow, respectively.
Figure 2 : Rheology measurement of colofFabb_HT sample
Figure 3 : Scheme of rheology measurement
Results
We have made different oscillating tests at different temperatures to see if the sample will act as a fluid or not at high temperature.
The data analysis for each sample is described in the following pages: Nylon 230 and nGen_Flex
Bibliography
