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Wet Chemistry

Dilute Solution Viscosity (DSV) is a key test method for the analysis of a polymer’s molecular weight and is a common quality control tool but also applicable to failure analysis.

Dilute solution viscosity which requires dissolving a polymer within a solvent and then measuring the time required to flow through a viscometer.  Once the flowtime is measured there are many options for calculations which include: Relative Viscosity, Reduced Viscosity, Inherent Viscosity, and Intrinsic Viscosity.

This data can be used for lot release testing of medical devices or for the failure analysis of parts where molecular weight degradation is anticipated.  A difference in the flowtime of a “good” vs “bad” part would indicate a change in molecular weight which results in a change in the physical properties of the part.  Since the sample size for dilute solution viscosity is typically less than 0.1 g, it is the preferred method when material degradation is anticipated.  Other methods include GPC which is more costly but provides significantly more data or melt flow index which requires 80-100 g of material and grinding of the failed part.


By measuring the flow time of a polymer solution through a precision capillary, we can measure the viscosity of that solution.  This is related to molecular weight of the polymer. 

Dilute Solution Viscosity is applicable to any soluble polymer but is commonly used for:

  • Polyethylene (PE)
  • Polypropylene (PP)
  • Poly(ethylene Terephthalate) (PET)
  • Poly(lactide) and Poly(glycolide) (PLA, PGA, PLGA)
  • Polyether ether ketone (PEEK)
  • Nylon (polyamide)

ASTM and ISO methods utilized or commonly referenced for custom testing

Sample Considerations

The sample must be soluble in a solvent and must be free of particles or fillers.  If those are present, we can use ultracentrifugation or filtration to remove them and ensure they don’t interfere with the measurement.  If a particle or filler is present at a high concentration, one option is to use TGA analysis to determine the wt% filler of the sample so it be accounted for.

Because these measurements are done using dilute polymer solutions, approximately 0.1 grams or less of polymer sample is needed.

For polymer dissolution, we use a variety of common organic solvents as well as hazardous solvents like hexafluoroisopropanol (HFIP), tetrachlorobenzene, trichloroethylene, and strong acids like nitric or sulfuric.

Contact us to talk through your specific sample considerations.


Dilute solution viscosity is applied in our lab daily to a very broad range of polymers and products.  Some examples include:

  • Ultrahigh molecular weight polyethylene (UHMWPE)
  • Lot release testing for bioabsorbable polymers (Poly(lactide), Poly(glycolide), Poly(caprolactone)
  • Molecular weight monitoring of bioabsorbable polymers during an aging study
  • Polyethylene glycol (PEG)Poly(hydroxyalkanoate) (PHA)
  • Glass-filled polyamides (Nylon) for failure analysis
  • Polyethylene terephthalate (PET) for failure analysis or lot release testing for manufacturing