Davenport density gradient column explained
With our density gradient columns it is possible to measure the density of a polymeric sample. The principle of a Davenport density column is simple and accurate: two different organic “solvents” with different densities are mixed in such a way that a density profile over the height of the column is obtained. By applying floaters with a predefined density to the column a calibration curve can be prepared. Polymeric samples with unkown densities can now be measured.
The use of the right “solvents” is essential for a good measurement. The polymeric sample shouldn’t dissolve or swell in the “solvents”. So, infact we need non-solvents for the specific polymeric samples. Next to that a combination of “solvents” should be found with different densities and good miscibility in a specific density range. We can measure the following polymeric samples (pellets, yarns, etc).
|PET||1289 – 1370 and 1330 – 1420 and 1360 – 1450|
|Polyamide||1030 – 1150 and 1130 – 1175|
|Polyacrylonitrile||1140 – 1280|
|Aramid||1415 – 1480|
|Carbon fiber||1500 – 2500|
|Cellulose||1440 – 1560|
The preparation of a Davenport density column is laborious and time consuming. Thereafter the column can be used for several weeks to months depending on the intensity of use. After a certain time period the gradient is disturbed and a new column has to be prepared.
Semi-crystalline materials can quenched in liquid nitrogen in order to measure the amorphous density of a material.