Transparent polymers

Viscosity number and IV value of polyesters (PC, PMMA, PET)


The mass worldwide pervasiveness of PET bottles and packaging makes recycling a necessity when it comes to protecting the environment and preserving resources. Here, the IV value, usually calculated according to the Billmeyer approximation, is the criterion for the quality of the recyclate and thus vital for further usage. Ideally, alignment with the original value of typically 80 cm³/g should be reached. With the mass-used plastics polycarbonate (e.g. CD-ROM), polymethylmethacrylate PMMA (e.g. Plexiglas) and others, the viscosity number (reduced viscosity) plays a similarly important role in production and re-use.

Even as early as in the production of the raw granule, e.g. polycondensation, the viscosity of the polymer solution is measured. Systems customized to operate in shifts have four to a maximum of eight measuring stations which are equipped with modules for automatic viscometer cleaning. Sample loading is done manually using a syringe or funnel. In 24-hour operation, these systems allow a sample rate of hundreds of samples. The restriction here is the time needed to dissolve the polymer which takes place in the magnetic stirrer at room temperature or at 80 or 130 °C. Here too there are affordable versions for just occasional measurements, e.g. for damage analyses and incoming and outgoing components inspections, which can be converted into fully automatic machines with samplers at later dates.

Recommended standards

  • DIN EN 1628-4/-5/-6
    Plastics – Determination of the viscosity of polymers in dilute solution using capillary viscometers –
    Part 4: Polycarbonate (PC) molding and extrusion materials
    art 5: Thermoplastic polyester (TP) homopolymers and copolymers
    Part 6: Methylmethacrylate polymers

Typical configuration

(Image similar)
(Image similar)

Measuring system PVS 1/4 with four measuring stands and automatic viscometer cleaning for fast, precise measurement


  • PVS 1/4 control unit
  • Four measuring stands S 5
  • Two VRM 4 cleaning modules for viscometer cleaning
  • High-quality PV 24 viscothermostat with external cooler
  • Ubbelohde glass viscometer of sizes 0c, I, and Ic (optionally with aspirating tube or in Micro-Ubbelohde version)



Automated sample preparation while using highquality Mettler weighing balances and dosing units.

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Applications Polymers

Technical polymers

Viscosity number of polyamides (PA) and polybutylene terephthalates (PBT)


Molar mass and IV value of polypropylene and polyethylene (UHMWPE)


Determining K-value acc. to Fikentscher (chain length of the basic polymers)

Medical Polymers

Molar mass and IV value of hyaluronic acid products and absorbable polymers

Cellulose and papers

Degree of polymerization of insulation paper using solution viscosity