r/ChemicalEngineering • u/_sixty_three_ • 11d ago
Research Polymer in solution measurement
I'm looking for types of analysis that can determine the % of polymer in a solvent solution. Anyone work in polymer industry that can help? Preferably continuous measurement but if samples need to be taken for lab analysis so be it
1
Upvotes
3
u/MuddyflyWatersman 11d ago edited 11d ago
yeah a loss on drying test can do it as long as you're not hot enough to decompose the polymer and you're not looking for overwhelming accuracy. at some point you can become diffusion limited getting the solvent out of the polymer so if 0.1-1% matters it's not easy to get to except by using vacuum or high heat for a long time.... and heat tends to break down and oxidize things of limited stability... depending on their temperature stability. there's usually a test called a TGA that will tell you at what temperature the polymer decomposes by say 1%.. during a constant ramp rate...
that's a measure of the temperature stability that's used commonly for products. is temperature stability is important when you begin extruding ... because extruders are hot.(thermogravimetric analysis) Quantitative NMR can as well especially in dilute solutions..... but they can take a sample and dilute it down by a known amount..100:1 ... and then do a quantitative NMR and that's going to give you probably a good answer. if you're looking for crude estimations.... viscosity will tell you about what the polymeric weight percent is if you know how it affects it. Unfortunately not a lot of places outside of universities and cutting edge companies do quantitative NMR. most NMR is qualitative. Density can even give it to you if you know the density of the solvent and how it changes with solution concentration. Ive generated curves and use density and temperature from a mass meter in the field to track solution ​concentration in the plant... accurate to within a couple %.. molecular weight and polydispersity of the polymer has to be pretty constant to use indirect methods to assess the concentration, and the solvent probably needs to be pretty low boiling to use loss on drying under atmospheric pressure.