PET- ISO 1628-5

Viscosity Number of PET and other thermoplastic polymers

The PSL Rheotek RPV-3 determines the viscosity number of poly(ethylene terephthalate) PET as well as other thermoplastic poyesters (PBT, PCT, PEN) in dilute solution using glass capillary viscometers in accordance with ISO 1628 Part 5. The test method requires a 0.5% concentration. A range of solvents are specified and for PET, the following are recommended - Phenol/1,2-dichlorobenzene, Phenol/1,1,2,2-tetrachloroethane, o-Chlorophenol or Dichlororoactetic acid (DCA). DCA solvent is typically used for high molecular weight PET.

Step by step

Solvent and solution flow times are measured at 25 deg. C using the same size of suspended-level Ubbelohde type viscometer for both measurements. Typically viscometer sizes 1C or 1B are used for PET applications. The method requires that two successive flow times are obtained within a 0.25% precision. In particular, the method states that successive flow times shall be measured without emptying or recharging the viscometer. It should be noted that the viscosity number of a saturated polyester will be dependent upon the solvent selected.

Customised combinations

The dual position RPV-3 (2) is an ideal configuration as well as the four position RPV-3 (4). The iSP-1 Sample Preparation system can be used in conjunction with the RPV-2 to prepare samples on a precise weight to weight basis. The iSP-1 takes into account insolubles such as fillers or glass fibre. Dissolution is carried out using a reaction block with stirring and heating at a closely controlled temperature (depending upon solvent) with a programmable timer (SD-BM).

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