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

Plastic wrap, e.g. for packaging and keeping food fresh, are usually made of polyethylene or polypropylene. Depending on the application, the molecular mass can vary quite strongly. As such, ultra-high molecular PE with molar mass >1,000 kg/mol is used in artificial limbs due to their outstanding gliding properties. The polyolefins are distinguished from most chemicals, solvents, and acids by their outstanding resistance to chemicals. For this reason, the solvents Decalin or Tetralin at 135 °C are usually used for solution viscometry. Since polymers quickly flocculate on cooling down, solutions previously were to be filled into the viscometer while hot, as was the solvent used for cleaning. A specially configured PVS system completely avoids contact with hot chemicals. In this case, the weighed samples are directly filled into an Ubbelohde dilution viscometer in the form of granules or powder using a funnel.

Then, the PVS program initiates the loading of the exact solvent quantity via special dosing units. Afterwards, a magnetic stirrer which is integrated into the thermostat is used to dissolve the sample at 135 °C and measure it. This is followed by the automatic emptying, cleaning, and drying of the viscometer. Along with the calculation of the IV value according to the Schulz-Blaschke approximation, it can also be determined directly using a dilution series (linear serial regression).

Measuring system PVS 1/2 with two measuring stands, integrated magnetic stirrer, and dosing units. Dissolving PE/PP samples directly in the glass viscometer – Automatic cleaning and recording of concentration series

• PVS 1/2 control unit
• Two measuring stands S 5
• A VRM 4/HT cleaning module for viscometer cleaning with external pump
• High-quality viscothermostat PV 15 operated with silicone oil at 135 °C
• Special Ubbelohde viscometers of size I for dissolving and diluting samples, incl. filter frit
• Integrated two-station magnetic stirrer with control console
• Two dosing units for the solvents Decalin and Tetralin
• Filling funnel for granulate and powder

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