ASTM D4889-21 Determination of Viscosity of Crude or Modified Isocyanates

ASTM D4889-21 test method is used to determine the viscosity of crude or modified isocyanates. This test method can be a pplied to toluene diisocyanate, methylene diphenyl isocyanate, and methylene phenyl isocyanate. The values are considered a standard when expressed in SI units.... Read More

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    ASTM D4889-21 is used for research, quality control, or specification testing to characterise isocyanates used in polyurethane products. The viscosity of a fluid is defined as its resistance to a uniform continuous flow without turbulence or other influences. Under specific conditions, some isocyanates display non-Newtonian behaviour.


    In ASTM D4889-21, enough samples are the smallest container to cover the immersion mark on the viscometer spindle and submerged in a constant temperature bath to the sample level. The mixture is stirred occasionally to avoid trapping air bubbles, and the temperature is checked at several different places within the container to verify consistency. The viscometer spindle is immersed into a sample to the immersion line. The viscosity of the specimen is tested using a 15-second rotation period. 

    Specimen Size:

    Laboratory humidity should be kept low, preferably about 50% relative humidity, because isocyanates react with moisture. Liquid samples with a viscosity of less than 100 000 mPa.s(cP) at 25°C must be tested at that temperature.


    Using the kinematic viscosity and the density of the sample, calculated the dynamic viscosity:

    η = v × ρ

    η= dynamic viscosity, mPa·s(cP)

    ρ = density, g/cm3

    v = kinematic viscosity, mm2/s

    Click here for additional information on Viscosity measurement.


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