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IS 13360-11-11 (1999): Plastics - Methods of Testing, Part11: Special Properties, Section 11: Polymers/Resins in theLiquid State or as Emulsions or Dispersions - Determin [PCD12: Plastics]

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IS 13360 (Part 11/Sec 11) :1999ISO 3219:1993

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Indian StandardPLASTICS METHODS OF

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TESTINGPART 11 SPECIAL PROPERTIES

Section 11 Polymers/Resins in the Liquid State or as Emulsions or Dispersions Determination of Viscosity Using a Rotational Viscometer with Defined Shear Rate

ICS 83.080 ; 17.060

@ BIS 1999

BUREAU OF INDIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

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April 1999 Price Group 4

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Methods of Test for Plastics Sectional Committee, PCD 23

NATIONAL FOREWORD

This Indian Standard (Part 11/See 11) which is identical with ISO 3219:1993 plastics_ polYmers/resins in the liquid state or as emulsions or dispersions Determination of viscosity using a rotationalviscometer with defined shear rate issued by the International Organization for Standardization(I SO) was adopted by the Bureau of Indian Standards on the recommendation of Methods of Test forPlastics Sectional Committee and approval of the Petroleum, Coal and Related Products DivisionCouncil.

The text of ISO standard has been approved as suitable for publication as Indian Standard withoutdeviations. Certain conventions are, however, not identical to those used in Indian Standards.Attention is particularly drawn to the following:

a) Wherever the words International Standard appear referring to this standard, they shouldbe read as Indian Standard.

b) Comma (,) has been used as a decimal marker while in Indian Standards, the currentpractice is to use a point (.) as the decimal marker.

In this adopted standard reference appears to one International Standard for which Indian Standardalso exists. The corresponding Indian Standard which is to be substituted in its place is listed belowalong with its degree of equivalence for the edition indicated:

International Standard Corresponding Degree ofIndian Standard Equivalence

ISO 291 :1997 Plastics IS 196:1966 Atmospheric Technically equivalentStandard atmospheres for conditions for testing (revised) with minor deviationsconditioning and testing

For tropical countries like India, the standard temperature and the relative humidity shall be taken as27 f 2C and 65 * 5 percent respectively.

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In reporting the results of a test or analysis made in accordance with this standard, if the final value,observed or calculated, is to be rounded off, it shall be done in accordance with IS 2:1960 Rules forrounding off numerical values (revised).

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IS 13360( Part 11/Sec 11 ) :1999ISO 3219:1993

Indian StandardPLASTICS METHODS OF TESTING

PART 11 SPECIAL PROPERTIES

Section 11 Polymers/Resins in the Liquid State or as Emulsions or Dispersions Determination of Viscosity Using a Rotational Viscometer with Defined Shear Rate

1 Scope

This International Standard specifies the general prin-ciples of a method for determining the viscosity ofpolymers and resins in the liquid, emulsified or dis-persed state, including polymer dispersions, at a de-fined shear rate by means of rotational viscometerswith standard geomet~.

viscosity determinations made in accordance withthis standard consist of establishing the relationshipbetween the shear stress and the shear rate. The re-sults obtained with different instruments in accord-ance with this standard are comparable and apply tocontrolled shear as well as controlled stress instru-ments.

2 Normative reference

The following standard contains provisions which,through reference in this text, constitute provisionsof this International Standard. At the time of publi-cation, the edition indicated was valid. All standardsare subject to revision, and parties to agreementsbased on this International Standard are encouragedto investigate the possibility of applying the most re-cent edition of the standard indicated below. Mem-bers of IEC and ISO maintain registers of currentlyvalid International Standards.

ISO 291:1977, P/astics Standard atmosphere for

conditioning and testing.

3 Principle

The viscosity of a fluid sample is measured using arotational viscometer with defined characteristics,which permits the simultaneous measurement of theshear. rate used and the shear stress applied.

The viscosity q is determined using the followingequation:

~=+Y

where

7 is the shear stress;

i is the shear rate.

According to the International System of Units (Sl),the unit of dynamic viscosity is the pascal second(Pa-s):

1 Pass= 1 N.s/m2

NOTES

1 Symbols are in accordance with ISO 31-3:1992, Quan-tities and units Part 3: Mechanics.

2 If the viscosity depends on the shear rate at which themeasurement is made, i.e. q =~(j), the fluid is said to ex-hibit non-Newtonian behaviour. Fluids with a viscosity inde-pendent of the shear rate are stated to exhibit Newtonianbehaviour.

t.4 Apparatus

4.1

4.1.1

Rotational viscometer

Measuring system

The measuring system shall consist of two rigid,symmetrical, coaxial surfaces between which the fluidwhose viscosity is to be measured is placed. One ofthese surfaces shall rotate at a constant angular vel-ocity while the other remains at rest. The measuring

1

IS 13360( Part 11/Sec 11 ) :1999ISO 3219:1993

*

system shall be such that the shear rate can be de- 4.3 Thermometerfined for each measurement.

The accuracy of the thermometer shall be +- 0,05 C.A toruue-measurirm device shall be connected to oneof the surfaces, this permitting determination of the 5 Samplingtorque required to overcome the viscous resistanceof the fluid. The sampling method, including any special methods

Suitable measuring systems are coaxial-cylinder sys- of sample preparation and introduction into the

terns and cone-and-plate systems, among others. viscometer, shall be as specified in the test standardfor the product in question.The dimensions of the measuring system shall be so The samples shall not contain any visible impuritiesspecified as to satisfy the conditions specified in an-

or air bubbles.nexes A and B, which are designed to ensure a ge-ometrically similar flow field for all types of It samples are hydroscopic or contain any volatile in-measurement and all common types of basic instru- gredients, the sample containers shall be tightlyment. closed to minimize any effects on the viscosity.

6 Test conditions4.1.2 Basic instrument

6.1 CalibrationThe basic instrument shall be designed to permit al-ternative rotors and stators to be fitted, for the gen-eration of a range of defined rotational frequencies(stepwise or continuously variable), and for measuringthe resulting torque, or vice versa (i.e. generation ofa defined torque and measurement of the resultingrotational frequency).

The apparatus shall have a torque-measurement ac-curacy within 2 YO of the full-scale reading. Wkhin theregular working range of the instrument, the accuracyof rotational-frequency measurement shall be within2 Y. of the measured value. The repeatability of vis-cosity measurement shall be + 2 Yo.

Viscometers shall be calibrated periodically, e.g. bymeasuring the torque characteristics or using refer-ence liquids of known viscosity (Newtonian fluids). Ifthe best-fit straight line drawn through the measuredpoints for the reference fluid does not pass throughthe origin of the coordinate system, within the limitsof the accuracy of the method, the procedure and theapparatus shall be checked more extensively in ac-cordance with the manufacturers instructions.

The viscosity of reference liquids used for calibrationshall lie in the same range as that of the sample(s) tobe measured.

NOTE 3 By using different measuring systems and rota-tional frequencies, most commercial instruments cover a 6.2 Test temperatureviscosity range from at least 10-2 Pass to 103 Pa+..

Generally, because of the temperature dependence

The range of shear rates varies greatly with different of the viscosity, measurements for comparison pur-

equipment. The choice of a particular basic instrument poses shall be carried out at the same temperature.

and appropriate measuring system shall be made by If measurements are required to be made at ambient

considering the range of viscosities and shear rates temperature, a measurement temperature of

to be measured. 23,0 C + 0,2 C is preferred.

Further details shall be as specified in the test stan-dard for the product in question.

4.2 Temperature-control device NOTE 4 Heat is dissipated in the sample during themeasurement. In the case of Newtonian liquids under adia-

The temperature of the circulating bath liquid or the ba~c test conditions, the rate of heat dissipation is given bytemperature of the electrically heated walls shall be vy (units W/m3) and may cause an increase in the tem-maintained constant to within + 0,2 C over the tem- perature of the sample.perature range O C to 50 C and to within + 0,5 Cat temperatures beyond these limits. 6.3 Selection of shear rate

,..,,

Closer tolerances (e.g. + 0,1 C) may be necessary The shear rate shall be as specified in the test stan-for more precise measurements. dard for the product in question.

2

IS 13360( Part 11/Sec 11 ) :1999ISO 3219:1993

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It is advantageous in the case of all Newtonian prod-ucts, and specially recommended in the case of non-Newtonian products, that measurements be made foras many shear rates (at least four) as possible, de-pending on the settings or programmed for rotationalfrequency (or torque in the case of fixed-shear-stressinstruments) allowed by the basic instrument, and atwidely differing shear rates so that a comprehensivegraph of viscosity vs. shear rate may be drawn.

In order to compare viscosities measured on differentinstruments, it is recommended that the shear ratebe selected from a series consisting of the following-values:

1,00 S-r 2,50 S-, 6,30 S-, 16,0 S-, 40,0 S-l,100 S-,250 S-;

or

1,00 S-, 2,50 S-, 5,00 S-, 10,0 S-, 25,0 S-,50,0 s-, 100 s-;

and these values multipled or divided by 100.

If a given basic instrument does not permit thesevalues to be selected, shear-rate values shall beselected from the viscosity curve.

In the case of non-Newtonian fluids, the measure-ments shall be stafled with increasing shear rates, i.e.increasing speed until the maximum speed isreached, and then decreasing the speed, making fur-ther measurements at decreasing shear rates.

NOTE 5 In this way, thixotropy and rheopexy can be as-sessed, although only qualitatively.

In the case of thixotropic and rheopexic liquids, thetest conditions shall be as specified in the test stan-dard for the product in question.

Prior to measurement, the sample inthe Viscometershall have sufficient time to recover any thixotropicstructure. This time will depend on the nature of theparticular sample.

If the readings at increasing and decreasing shear rateshow only random differences, the two readings maybe averaged. If a consistent difference is observed,as in the case of thixotropic systems, both valuesshall be recorded.

6.4 Procedure

Unless otherwise specified by the test standard forthe product in question, make three determinations inaccordance with annex A or B, as applicable, eachwith a new portion of the sample.

For the evaluation of the viscosity measurements. seeannexes A and B.

If the viscosity of a particular product is required tobe measured at different temperatures, determine theviscosity curve at each temperature with the samesample portion, provided the measuring system of thesize chosen remains suitable (the fact that the vis-cosity varies with temperature means that it may benecessa~ to change the measuring system).

For each repeat determination, use a new sample ifpossible, and determine the viscosity by commencingwith increasing temperatures and sub-sequently usingdecreasing temperatures.

Prior to measurement, the sample in the viscometershould have sufficient time to attain the requiredtemperature.

7 Expression of results

Calculate the viscosity q in pascal seconds, using therelationships given in the instruction manual or thetables or nomograms attached to the apparatus. Cal-culate the arithmetic mean of the three determi-nations.

When stating viscosity values, give, betweenparentheses, the temperature and shear rate at whichthe viscosity was measured, e.g.

rI(23 C, 1 600 S-l) = 4,25 Pa-s

Where viscosity measurements are made at differenttemperatures and shear rates, plot curves to demon-strate these relations.

8 Test report

The test report shall include the following information:

a)

b)

c)

d)

e)

f)

the number and year of publication of this inter-national Standard;

all details necessary for identification of the ma-terial tested;

the date of sampling;

the test temperature in degrees Celsius;

details of the preparation of the sample;

a description of the viscometer measuringused;

system

.,

3

IS 13360 ( Part 11/Sec 11 ) :1999ISO 3219:1993

g) a viscosity curve plotted from all the correspond-ing values of the shear stress 7, in pascals, andthe shear rate j, in reciprocal seconds, obtained;

h) in the case of single-point measurements, theviscosity, including the temperature and shearrate at which the determination was carried out(see clause 7);

i) in the case of thixotropic and rheopexic liquids,the conditions, e.g, ramp times and total shear,used;

j) the measurement times (i.e. the periods of timewhich elapsed, after the required shear rate hadbeen reached, before even reading was made);

k) the individual results of the viscosity determi-nations, in pascal seconds or millipascal seconds,and the arithmetic mean of these results;

1) any test conditions that have been agreed uponbut which deviate from this International Stan-dard, e.g. the use of measuring systems of dif-ferent dimensions;

m) the date of the test.

(- IS 13360 ( Part 11/Sec 11 ) :19991ISO 3219:1993

Annex A(normative)

Coaxial-cylinder viscometers

A.1 System characteristics

The measuring system comprises a cup (i.e. the outercylinder with a closed base) and a bob (i.e. the innercylinder with the shaft as shown in figure A.1 ). Thebob may act as the rotor and the cup as the stator,or vice versa.

A.2 Methods of calculation

The shear stress 7 and the shear rate j are not con-stant over the annular cross-section of rotational vis-cometers with coaxial cylinders, but decrease fromthe inside to the outside (Searle type) or vice versa(Conette type). Moreover, the variation in j also de-pends on the theological propetiies of the materialunder test.

It is convenient to calculate T and j asrepresentativeValuesl)which do not occur at thesurface of the measuring system itself (i.e. at the ex-ternal radius re or the internal radius q), but at a certaindistance inside the annulus. It has been shown (bothby theory and experiment) that the representativevalues ~rePand j,,P, as calculated from equations (A.2)and (A.3), describe, to a very good approximation, theflow behaviour of fluids with a local power law indexin the range 0,3 to 2,

The shear stress, expressed in pascals, is calculated,using equations (Al ) and (A.2), from the torque Mmeasured at the inner cylinder (i.e. at radius q) or atthe outer cylinder (i.e. at radius re), these two radiibeing expressed in metres.

Ti =M . ~= M

. (Al)2xLr~C~ e 2nLr~C~

Ti + 7 l+6*x T,_l+#x Trep = =

-

2 262 2 e

_l+d2x M. . . (A,2)

2132 2nLr/k~

where, in addition to the above-mentioned quantities

M is the torque, expressed in newton metres;

6 is the ratio of the radius of the outer cylinderto that of the inner cylinder;

L is the length, in metres, of the inner cylinder;

q is an end-effect correction factor that ac-counts for the torque acting at the end facesof the measuring system (this correctionfactor depends on the geometry of themeasuring system and on the theologicalproperties of the liquid, and must be deter-mined experimentally for each type ofmeasuring-system geometry).

The representative shear rate, expressed in radiansper second, is obtained from

-{

. 1+C52Yrep=@x62_1 . . . (A.3)

where co is the rotational velocity, in radians per sec-ond.

If the rotational frequency n is expressed in rev-olutions per minute, then

.=:: =o,lo47n

A.3 Standard geometry (see figure A. 1) ~.The dimensions of this type of measuring systemmatched to a given viscometer are based on the fol-lowing ratios ensuring a geometrically similar flowfield for all tasks and basic instruments:

1) See Giesekus H. and Langer G.: Determination of the true flow curves of non-Newtonian liquids and plastics using therepresentative viscosity method, Rheo/ogica Acts, 16, 1977,No. 1, pp. 1-22.

5

IS 13360( Part 11/Sec 11 ) :1999ISO 3219:1993

. .4

b is the

L. is the

L. is the

L is the

q is the

e is the

rs is the

6=+=1,0847

L _ ,r,

rs=0,3q

a=120

*

ratio of the radius of the outer cylinder to that of the inner cylinder;

length of the inner cylinder;

distance between the bottom edge of the inner cylinder and the bottom of the outer cylinder;

length of the immersed part of the shaft;

radius of the inner cylinder;

radius of the outer cylinder;

radius of the shaft;

a is the apex angle of the cone at the bottom of the inner cylinder.

NOTES

1 The cone at the lower end of the inner cylinder facilitates insertion of the cylinder into the cup filled with the liquid undertest without causing the formation of air bubbles.

2 Coaxial-cylinder systems require precise alignment of the axes of the inner and outer cylinders.

Figure A,l Standard-geometry coaxial-cylinder system

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IS 13360( Part 11/Sec 11 ) :1999ISO 3219:1993 d

The sample volume depends only on the radius q andis given by the equation:

Forthethe

V=8,17r~ . . . (A.4)

measuring systems with this standard geometry,end-effect correction factor CL is independent ofradius q. For Newtonian liquids,

CL=l,10

has been found as an empirical value. For non-Newtonian liquids, CL is not constant, but depends onthe shear rate jI and on the theological properties ofthe liquid.

NOTE 6 For shear-thinning liquids, CL may reach valuesof up to 1,2 at certain shear rates. For visco-plastic liquidsexhibiting a yield value, CL values of up to 1,28 have beenobserved at low shear rates.

Using CL= 1,10 (Newtonian liquids), 62= 1,17657and ~r~P= 0,925~i = 1,0887,, the following numericalrelationships are obtained if the representative shearstress Trepis expressed in pascals, the torque M innewton metres, the representative shear rate jJr~Pandthe rotational velocity o in radians per second, theinternal radius q in metres and the rotational fre-quency n in reciprocal minutes:

~,,P = 0,0446 X ~ ,.. (A.5)r,

j+,~ = 12,33 w = l,291n . . . (A.6)

A.4

If forused,

Other geometries

any reason the standard geomet~ cannot bemeasuring systems of other dimensions may

be chosen. In o~der to use the methods of calculationgiven in A.2, the following requirements shall be met:

+- lr,

v

90< a< 150

The end-effect correction CL has different (usually

1

!

higher) values from those with the standard ge- ---,4ometry.

NOTE 7 The choice of a narrow annulus, e.g. d

A*L

IS 13360( Part 11/Sec 11 ): 1999ISO 3219:1993

Annex B(normative)

.

Cone-and-plate system

B.1 System characteristics B.2 Method of calculation

The measuring system consists of a rotating cone and If a< 0,05 rad (i.e. a< 3), the following equationsshaft and a stationary plate (see figure B. 1). are applicable for the calculation of the shear stress 7

The angle a between the cone and the date shall beand shear rate j.

as small as possible, preferably not greater than 10 ~= 3M (B.1)and in no case greater than 4. When the angle is 2nr3

. . .

greater than 10, this shall be stated in the test report.The advantage of the cone-and-plate system is that, i=: . . . (B.2)at such small angles, the shear rate across the conicalgap may be considered constant. where

M is the torque, in newton metres;

r is the radius, in metres, of the cone;

a is the angle, in radians, between the coneand the plate (1 rad = 1800/K);

Ii) is the angular velocity, in radians per second.

+In order to avoid friction caused by contact betweenthe cone and the plate, truncated cones can be used.

M

This configuration can also be used if the liquid undertest contains solid particles.

Cone-and-plate systems require precise alignment ofthe cone axis perpendicular to the plate and also exactsetting of the point of contact between the apex ofthe cone and the plate (or exact setting of the gap inthe case of truncated cones).

Precise filling of the gap between cone and plate isalso important (do not overfill or underfill).

NOTE 8 The fact that the gap width changes with tem-Figure B.1 Cone-and-plate system geometry perature will also have to be taken into account.

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Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of /ndian Standards Act, 1986 topromote harmonious development of the activities of standardization, marking and qualitycertification of goods and attending to connected matters in the country.

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This Indian Standard has been developed from Doc : No. PCD 23 (1580).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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