I'm currently studying on pyrolysis of low density polyethylene (LDPE) pyrolysis, and I'm required to setup a GPC instrument using Waters ultrastyragel columns to determine the molecular weight distribution of the pyrolysis products. I would also like to obtain the molecular weight distribution for the LDPE sample I'm using. When refer to literature, the pyrolysis products can be analyzed using GPC at 40oC, however, analysis of the polymer itself is rarely mentioned, and I heard that this can only be achieved using high-temperature GPC (HT-GPC). Is it possible to set up HT-GPC using the columns I have? Or I have to purchase other columns for such purpose?
As I have no experience in using GPC, thus any answer and experience sharing regarding the use or setup of GPC would be appreciated.
Hello
You will very probably have to use high-temperature GPC, at least that was the case for LLDPE and HDPE. We had such samples measured at 150°C, if I remember correctly. Regarding the apparatus, you probably have to get dedicated equipment, but you can surely find the temperature limitations of your column on the manufacturers website or in the user manual.
If you would be interested in any manufacturers, try looking at Polymerchar. There you would certainly find the necessary equipment (and maybe relevant application notes). I would guess that you can also discuss you application directly with the company.
Regards
Josef
Hi
using GPC with styragel columns using trichlorobenzene as a solvent, you will get the molar mass of the virgin polymer ...
if you want to determine the molar mass of your pyrolysis products, which is very low, you should better use GC MS
@Josef, thanks for the answer. I'll contact the manufacturer for more information on HT-GPC.
@Emmanuel, in my study, the LDPE is dissolved in a solvent, then the solution is fed downward into the reactor. When reaching the catalyst bed, there is very short retention time for LDPE solution to undergo cracking process. Then, the cracking products flow into the product collection system. However, there is a possibility that not all LDPE molecules undergo complete cracking within the short retention time. Thus, my supervisor strongly suggest that I should use GPC to determine the molecular weight distribution of the liquid product, hence estimate the degree of cracking of LDPE in the process. Of course, GC-MS is also used to determine the products with low molecular mass.
My process design is similar to the Riser Simulator as used in the attached publication, except that retention is lower. Any suggestion on the use of GPC is appreciated.
Article Valorization of the Blends Polystyrene/Light Cycle Oil and P...
ok, if I understand well, HT GPC is the right tool.
Agilent sells good apparatus too. You can work at 135-150°C. You have to pay attention that your polymer is first totally soluble in the trichlorobenzene at the investigated temperature.
regards
Dear Wong Syie Luing, ·
HT-GPC is the method of choice. Very low molar mass polyolefins (M lower than approx 1000g/mol) might be run in THF. The main instrument manufacturers for HT-GPC have been mentioned in above answers.
Polyolefins are typically run at 150 °C in TCB. Some people use standards SDV columns even at such high temperatures. However, this is something I would not recommend as these columns will probably degrade faster than materials dedicated for HT-GPC. A 3 column set costs in the order of 3000-5000€, therefore it will probably be better to apply special HT-column, e.g. PSS Polefin columns.
Is your equipment suitable for HT-GPC at all? Even small "cold" zones will result in precipitation of high molar mass polyolefins, which might block your capillaries. Thus you will need dedicated HT-Equipment.
Also keep in mind that GPC requires matching the pore sizes of the column to your materials. As your products might be of low molar mass, you probably require a good resolution in the low molar mass region for your degradation products, while a different column set might be required for the original high molar mass samples.
Depending on the number of samples to be run, it might be an alternative to use sample testing services.
Best regards
Wolfgang
Thanks for the detailed explanation.
I have Waters Ultrastyragel columns with pore size ranges from 100A to 105 A. Although it is stated in the user manual that use of columns higher than 40oC is possible for the columns, the manufacture of the columns 103, 104, and 105 A has been phased out by the manufacturer years ago, thus even the company representative could not guarantee the column performance at high temperature.
Thus, I'll consider the sample testing service, or may be MALDI-TOF.
Best Regards.
High temperatura GPC is required for its determination, but I did it once by viscosimetry, it is a hard task but it is posible, using all the time the solvent at higher temperature and considering the change in volumen of the solvents due to that temperatura. In the handbook of polymers are the constants and solvent for this purpose. It is necessary also to have a constant bath who did not change the temperature as high as 85 degrees and one digital equipment to measure the pass of the solvent in the marks without see it.
Hi Wong Syie Luing
MALDI will not work, as the low polaraity prevents ionization. In addition, I expect that the MW of your parent polymer is too high.
The main role is still played by the right choice of equipment. For analysis of MMP polyolefins better use GPC PL-GPC 220. Highly system PL-GPC 220 works with almost any combination of polymers, solvents and temperature conditions and is fully automatic and highly accurate detection of temperatures from room temperature to +220 °C. It allows you to set up to 6 chromatography columns and incorporates except refractometric detector also viscometric detector and light scattering detector.
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