ISO 1628-1-2021 pdf download.Plastics一Determination of the viscosity of polymers in dilute solution using capillary viscometers一 Part 1: General principles.
6.2 Concenlratlon
Where no standard exists. careful consideration shall be given to the choice or solvent and he solution concentration. The solution concentration idiall be chosen so that the ratio of the cifiux time of the solution to the efflux rime olthe solvent is at least 1.2 and less than 2.0.
NOTE A tower limit of 1,2 enswes suflicient precIsion or the measured difference In efflux times, The uppt’i limit of 2,0 prevents shear effects and nonlinearity of thr viscosity number in relation to concentration that can occur at higher molecular masses.
MarL’ than one concentration can therefore be used for a given polymer/solvent system, depending on the molecular mass olthc polymerunder test.
The concentratIon is preferably expressed In kg/rn’ of solution or as the multiple lot kg/rn’, Le. gJcm.
7 Temperature of measurement
The temperature shall be chosen with due regard to sufficient soluhility 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 5C shall be chosen whenever possible. It another temperature is used, use the temperature that was agreed between the partses concerned and stated In the test report
8 Procedure
0.1 General
Measure the efflux times for the solution and the solvent successively in the same viscoqneter. using the procedure described in 112 and 11.3.
0.2 Preparing and charging the viscometer
8.2.1 MaIntain the bath at the specified test temperature.
8.22 Charge the dry, dean viscometer (the deanthg procedure Ii specified In Annex A) by tilting ii about 30 from the vertical and pouring suffIcient liquid through tube L (Ste Figurci or Fiturc2 so that. when the viacometer is returned to the vertical, the meniscus is between the filling marks G and H. Avoid trapping air bubbles in the viscometer. The initial tilling may be carried out away h’oin the bath.
82.3 Mount the vtscometer in a holder in the bath, ensuring that tube N is vertical. Allow Lime for the charged viscometer to reach the temperature of the bath. Usually. 15 miii will suffice if the measwvlnent is to be made at 25 5C. At higher temperatures, longer times is necessary. tJnneces.cary debyx should be avoided as it is found that the most consistent results are obtained shortly after temperature equilibrium is attained with a freshly charged viscometer.
8.2.4 This procedure shall also be followed when a measured amount of solvent is added to a solution, already contained in the vlscomcter, La order to create a more dilute solution for additional drterininahonui. the additional solwnt shall he maintained at the specified test temperature prior to use
8.2.5 In automated equipment, the viscometer Is fixed in the vertical position within a temperature’ controlled bath and the apparatus is designcd to till the viscomneter with liquid in this position The bath shall be maintained at the specified test temperature and an equilibration tune selected in accordance with 112.3.ISO 1628-1 pdf download.