ISO 1628-1:2021 pdf – Plastics — Determination of the viscosity of polymers in dilute solution using capillary viscometers — General principles.
1 Scope This document defines the general conditions for the determination of the reduced viscosity, intrinsic viscosity and K-value of organic polymers in dilute solution. It defines the standard parameters that are applied to viscosity measurement. This document is used to develop standards for measuring the viscosities in solution of individual types of polymer. It is also used to measure and report the viscosities of polymers in solution for which no separate standards exist. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3105, Glass capillary kinematic viscometers — Specifications and operating instructions ISO 80000-1, Quantities and units — Part 1: General ISO 80000-4, Quantities and units — Part 4: Mechanics 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 80000-1, ISO 80000-4 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/
6.2 Concentration Where no standard exists, careful consideration shall be given to the choice of solvent and the solution concentration. The solution concentration shall be chosen so that the ratio of the efflux time of the solution to the efflux time of the solvent is at least 1,2 and less than 2,0. NOTE A lower limit of 1,2 ensures sufficient precision of the measured difference in efflux times. The upper limit of 2,0 prevents shear effects and non-linearity of the viscosity number in relation to concentration that can occur at higher molecular masses. More than one concentration can therefore be used for a given polymer/solvent system, depending on the molecular mass of the polymer under test. The concentration is preferably expressed in kg/m 3 of solution or as the multiple 10 3 kg/m 3 , i.e. g/cm 3 . 7 Temperature of measurement The temperature shall be chosen with due regard to sufficient solubility and other technical requirements, but kept constant for any particular polymer/solvent system. The temperature tolerance shall be specified. A temperature of 25 °C ± 0,05 °C shall be chosen whenever possible. If another temperature is used, use the temperature that was agreed between the parties concerned and stated in the test report. 8 Procedure 8.1 General Measure the efflux times for the solution and the solvent successively in the same viscometer, using the procedure described in 8.2 and 8.3. 8.2 Preparing and charging the viscometer 8.2.1 Maintain the bath at the specified test temperature.
8.3? Efflux? time? measurement See Figure 1 or Figure 2. Close tube M and apply suction to tube N, or pressure to tube L, until the liquid reaches a level about 5 mm above mark E. Hold the liquid at this level by closing tube N. Open tube M so that the liquid drops away from the lower end of capillary tube R. When the liquid is clear of the end of the capillary and the lower end of tube M, open tube N. Measure the efflux time to the nearest 0,2 s as the time taken for the bottom of the meniscus to pass from the top edge of mark E to the top edge of mark F. For polymer solutions containing small amounts of finely divided pigments, such as carbon black, it shall be necessary to view the top of the meniscus. Where large concentrations of pigments are involved, it shall be necessary to centrifuge the solution before proceeding. The opening and closing of the tubes may be carried out conveniently by means of taps or clips on clean flexible tubing attached to the ends of the tubes, making sure that no fluff or other contaminant enters the tube. The first flow shall not be taken into account for measuring the efflux time. Repeat the measurement of efflux time immediately, without emptying or recharging, until two successive efflux times agree to within 0,25 %. Take the mean of these two values as the efflux time. If two successive determinations of the mean efflux time of the solvent differ by more than 0,4 s, clean the viscometer as specified in Annex A. The efflux time for any “new” solution, created by the addition of solvent to an existing solution held in the viscometer, shall be determined as a separate liquid, in accordance with this procedure.