The average molecular weight of macromolecules was measured with a dilution type Ubbelohde viscometer
1. Diluted Umbrella viscometer, only suitable for those who dissolve the sample, that is, add a certain volume dilution, the sample is easy to dissolve again, without stirring and so on.
2. Water-soluble samples are more suitable for dilution-type black capillary viscometer, organic phase, especially relatively viscous DMF solvent, not suitable for dilution capillary viscometer.
3. dilution of the viscosity of the pipe itself there is an error, generally used for production enterprises quality inspection, such as: chemical fiber plants, etc., require faster, not so accurate all the situation.
4. Scientific research is more suitable for non-dilute type, especially similar to DMF and other viscous solvents.
5. With the Ubbelohde viscometer to measure the average molecular weight of the polymer can refer to the empirical formula (polyester, nylon are applicable), M = (relative viscosity -1) × 10500.
6. Measure several points, that is, more than a few different concentrations of time.
7. With non-dilution capillary test, if the test time is abundant, and the same type of capillary has several roots, or can guarantee the capillary viscometer clean, then you can measure several different concentrations of time, so with more Point extrapolation method to calculate the intrinsic viscosity, and more accurate.
8. The tester should prepare the sample solution in advance, in particular, to ensure that the sample solution dissolved fully, completely, in line with the requirements of the standard method, and the concentration is known, accurate!
Do the same viscosity test and do GPC test the same place, that is, to dissolve the sample to be sufficient, complete, otherwise the data is not accurate. This is why dilution-type capillaries are limited because the dilution capillary itself is smaller than the non-dilution type, but is still relatively small, at least not suitable for dissolving those solvents that are viscous or have a very high intrinsic viscosity Samples, such as polyolefin samples, polyacrylamide samples are typical, too much viscosity, it is not suitable for dilution capillary. In addition, the exact dilution of the concentration, for the dilution of the capillary, it is also a problem. Due to the small size, a little error in the operation may cause the concentration to be inaccurate.
| |
| |
|
没有评论:
发表评论