scope:

This part of ISO 1628 defines particular conditions for determining the viscosity number and limiting viscosity number of polyethylenes and polypropylenes at 135°C in dilute solution. It is applicable to low, medium and high-density polyethylenes and to a wide range of polypropylenes, including pure isotatic, stereoblock and atactic polymers. The viscosity of polymer solutions may be affected by additives present in the sample. The value of a viscosity number determined by this method may therefore be unreliable if the sample contains fillers or other additives.