Viscosity Measurement Principle

Viscosity Measurement Principle

The liquid flows through a pipe
A parabolic velocity distribution in a tube
Hagen-Poisee's Law (Gravity-Driven Flow)
Vkin = C * t; C = pr4hg / (8Vl)
C: Capillary constant
R: the radius of the capillary
H: height of liquid column
V: the volume of liquid passing through the capillary at time t
L: the length of the capillary

Principle of capillary viscosity measurement
     Measure a given volume of sample through a capillary of a known size at a given temperature and at accurate time.
     Good external conditions:
1. Temperature fluctuation: <0.1 ° C requires constant temperature bath
2. Precise timing function
3. Excellent cleanliness of the capillary
4. Sample dust and particles

Measurement of Ubbelohde viscometer

Determine the correct capillary
Vkin = C * t
     According to a given viscosity and standard, (recommended) 100 seconds of measurement time, (minimum time of about 60 seconds), you can determine the required Ubbelohde viscometer
For example: Vkin = 35 mm2 / sec
     T = 100 seconds should be used
    Constant K = 0.3; type IIc
     The capillary viscometer can not be measured: non-Newton-liquid rheological properties (eg paste, polymer melt, concentrated latex and solution) can measure: pure, organic mixtures and inorganic liquids (eg water, Polymer, protein or other organic dilute solution, (mineral) oil; capillary viscometer has a very high accuracy (<0.1%), the conditions required for the temperature stability <0.1 degrees!

The basic formula of Kinematic viscosity

Rules
Well-known rules:
     According to ISO3105 and ASTM445 / 446 minimum flow time should be not less than 200 seconds
People do not know but the important rules:
     According to ISO3105 and ASTM445 / 446 if the "kinetic energy correction", then the minimum flow time can be less than 200 seconds.
For the "kinetic energy correction" method, the flow time is reduced to 40 ... 60 seconds is possible to meet all the criteria and save time! But the kinetic correction value can not be greater than 3% of the outflow time t (ie ⊿t / t ≯ 3%)
Uzbek and other types of capillary viscometer

How to test the viscometer with Capillary tube GBGB17931-2003

A . 1 RangeThis method suits for testing the viscosity of  PET polymer and copolymer-determination.

A 2 Principle

Under 25±0.02 ℃ ,Determination Solvent and concentration of 0. 005 g/ml, PET resin solution flow out of time, then work out the viscosity of known concentration .

A . 3 Reagents
Unless other stated, only in the analysis using  pure  grade reagents.
A . 3. 1 Phenol
A . 3. 2  1.1.2.2-Tetrachloroethane
A . 4  Instrument
A . 4. 1 Constant temperature water bath:  (25± 0.02) ℃。
A. 4. 2 Ubbelohde viscometer:ISO 1628-1:1998 1B type Capillary Viscometer (Φ= 0. 88 mm ) ; or other type viscometer

Remarks: ISO 1628-1 :1998 1B type capillary viscometer (Φ= 0. 88 m m ) can make sure the Solution  of flow time from 80 s to 200 s.

A . 4. 3

Heating device: to control the temperature at(110± 10) ℃  oil bath or other heating(1 10 ±1 0) ℃ device.

A. 4. 4 Magnetic stirrer or other stirrer device.

A . 4. 5

Diameter (63-90) μm stainless steel filter or micro-pores diameter for (40^-1 00) μm glass filters
A . 4. 6 Analytical balance: minimum Division value of 0.1 mg,
A. 4. 7 Stopwatch: minimum Division value of 0.1 s Or automatic timing stopwatch.

4. 8 Pipette: 25 m l. Automatic  liquid  filling  apparatus  can be used.

A .4. 9 Erlenmeyer flask: 50 m l, 100 m l, with  glass stopper.

4. 10 Density Meter: range (1.200^ 1.300) g/cm 3

A . 5  Prepare Solvents and  sample solution
A . 5. 1  Preparation of solvents
A . 5. 1. 1  Put the reagent bottle containing phenol (A. 3. 1) into a hot water bath at about 60 ℃ to melt the phenol
A . 5. 1. 2  Wipe the water out of the phenol reagent bottle，The phenol and 1, 1, 2, 2-tetrachloroethane (A. 3.2) were weighed at a mass ratio of 60:40 (Accurate to 1%) after loading another reagent bottle and shake to mix well.
A . 5. 1. 3  The prepared solvent was filtered through a stainless steel filter (A. 4. 5) or a glass filter (A. 4.6) into a stoppered brown glass. Place it 24 h for using.
A . 5. 1. 4  Test the density of prepared solvent in a constant tepperature water bath (A . 4. 1)  at （25 ±0.02）℃。 The solvent density should be controlled in the range of (1.235士0.003) g/cm3
For the solvent in using,pls measure the average outflow time at A.6.4.

If the average time exceeds 1% of the initially data,this solvent should be discarded and a new solvent should be prepared

 

A. 5. 2  Preparation of Sample solution

5. 2. 1 Weighed (0.1250±0.0010g) sample in 50 ML or 100 ML Cone bottle(a.4.9).

A. 5. 2. 2 Using Pipette (A.4.8) or Automatic pipetor measuring 25 ml phenol/ 1.1.2.2 Tetrachloroethane Solvent(A.5.1) into cone bottle.
A . 5. 2. 3 Placed the cone bottle contains solvent on a heating device (A.4.3) at the temperature of (110 ±10)℃.Provided constant heating and stirrer（A.4.4）,make the sample dissolved completely. The dissolution time controlled within 30 minutes. If this time is exceeded, it needs to be re-dissolved.

When the sample dissolving finished, cool to room temperature.
A . 6 Steps

A . 6. 1 Preparation
A . 6. 1. 1  The sample solution is filtered through a stainless steel filter or glass funnel then added to an Ubbelohde viscometer (A.4.2). The liquid level of the solution should be between the markings.
A. 6. 1. 2  Place the viscometer vertically in a constant temperature water bath (A. 4. 1) at (25 ± 0. 02) ° C. The upper scale of the viscometer is lower than the constant temperature water surface at least 30 mm. The viscometer should be placed in a constant temperature water bath for about 20 m in order to reach a temperature of (25 ± 0. 02) ℃
A . 6. 2  Determination of flow time of the sample solution

Measuring 3 times of effluent under the circumstances of not emptying and reloading the new solution. Make sure the max value and minimum values does not exceed 0.2s.Take average of 3 flow time as the sample solution flow time t.
A . 6. 3 Determination of flow time of the solution

Take about 17 ml of solvent, using the same method as A . 6. 2 5 times , and make sure the max and minimum values does not exceed 0.1s. Take average of 3 flow time as the sample solution flow time t0. For the solvent in use measure the average flow time a least one time a day.If the difference in the average outflow time of two consecutive measurements is greater than 0.2s,the viscometer should be cleaned..

Remarks: Cleaning the viscometer：Put the viscometer in the solution of sulfuric acid- potassium dichromate(i, 1 by volume) more than 12 h before using or measured value is not parallel
Remove the concentrated sulfuric acid and potassium dichromate,

washed with water first then washed with ionized wate (or Distilled water) at least 5 times, and then cleaned with acetone 1 time. At last dry the viscometer in less than 100 ℃.When the viscometer is in use,washed the test solution first,then washed with Trichloromethane, at last dry it.
A . 7  Calculation results

I represent for viscosity of PET solution. using the formula (A.1),In milliliters per gram (m L / g),

Remarks :

t0---Solvent outflow time, in seconds (s)
t- Flow time of the solution, in seconds(s) ,
c — Solution concentration，in units of grams per milliliter (g/m l) .

Take the average of the two parallel determinations as the test result. And fix the four significant digits according G B / T 81 70- 1987.

Note: ISO 7792-1: 1997 provides that the viscosity number is one of the characteristic properties of PET resin naming

The intrinsic viscosity of the PET resin solution is expressed [η] in terms of the amount indicated by the formula (A. 2) in units of dl / g 

Remarks:
c— The concentration of the solution in grams per minute (g / dL):
ηr—The relative viscosity

Take two parallel determination average as the test result and take three decimal places according GB/T 8170-1987