EN ISO 8985:1998

SLOVENSKI STANDARD
01-maj-1999
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Plastics - Ethylene/vinyl acetate copolymer (EVAC) thermoplastics - Determination of
vinyl acetate content (ISO 8985:1998)
Kunststoffe - Ethylen-Vinylacetat-Copolymer (EVAC)-Formmassen - Bestimmung des
Vinylacetatgehalts (ISO 8985:1998)
Plastiques - Copolymeres éthylene/acétate de vinyle (EVAC) thermoplastiques - Dosage
de l'acétate de vinyle (ISO 8985:1998)
Ta slovenski standard je istoveten z: EN ISO 8985:1998
ICS:
83.080.20 Plastomeri Thermoplastic materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 8985
Second edition
1998-03-01
Plastics — Ethylene/vinyl acetate
copolymer (EVAC) thermoplastics —
Determination of vinyl acetate content
Plastiques — Copolymères éthylène/acétate de vinyle (EVAC)
thermoplastiques — Dosage de l'acétate de vinyle
A
Reference number
ISO 8985:1998(E)
ISO 8985:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 8985 was prepared by Technical Committee
ISO/TC 61, Plastics, Subcommittee SC 9, Thermoplastic materials.
This second edition cancels and replaces the first edition (ISO 8985:1989),
which has been technically revised.
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
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Printed in Switzerland
ii
©
INTERNATIONAL STANDARD  ISO ISO 8985:1998(E)
Plastics – Ethylene/vinyl acetate copolymer (EVAC) thermoplastics –
Determination of vinyl acetate content
1 Scope
This International Standard specifies two categories of method for the determination of the vinyl acetate
(VAC) content of ethylene/vinyl acetate (EVAC) copolymers, for use in the designation of such
copolymers in accordance with ISO 4613-1:1997. One category is referred to as "reference methods", the
other as "test methods".
Note – The abbreviation previously used for ethylene/vinyl acetate copolymer (E/VAC) has been replaced by the abbreviation
EVAC (see ISO 1043-1:1997, Plastics – Symbols and abbreviated terms – Part 1: Basic polymers and their special
characteristics).
The "reference methods" are used to calibrate the method used for the determination of the vinyl acetate
content of ethylene/vinyl acetate copolymers.
The "test methods" are other methods which can be used for the determination if they are calibrated using
one of the reference methods described in clause 3 provided they show a certain permissible repeatability.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of
this International Standard. At the time of publication, the editions indicated were valid. All standards are
subject to revision, and parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the standards indicated below. Members
of IEC and ISO maintain registers of currently valid International Standards.
ISO 4613-1:1993, Plastics – Ethylene/vinyl acetate (E/VAC) moulding and extrusion materials – Part 1:
Designation and specification.
ISO 4799:1978, Laboratory glassware – Condensers.
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ISO 8985:1998(E) ISO
3 Reference methods
3.1 Reference method 1: Hydrolysis and back titration
3.1.1  Principle
A test portion is dissolved in xylene and the acetate groups are hydrolysed with alcoholic potassium
hydroxide solution. An excess of sulfuric or hydrochloric acid is added. The acid is back titrated with a
standard sodium hydroxide solution in the presence of phenophthalein as indicator.
3.1.2  Reagents
During the analysis, use only reagents of recognized analytical quality and distilled water or water of
equivalent purity.
3.1.2.1 Xylene.
3.1.2.2 Sulfuric acid, approx. 5g/l solution, or hydrochoric acid, approx. 3,7g/l solution.
3.1.2.3 Potassium hydroxide, approx. 5,6g/l ethanol solution.
Dissolve 5,6g of solid potassium hydroxide (KOH) in 500ml of ethanol, make up to 1000ml,
leave to settle until the next day and decant the clear part of the solution.
3.1.2.4 Sodium hydroxide, standard solution, c(NaOH) = 0,1 mol/l.
Note – The nomenclature c(xxxx) is preferred to [xxxx] and used throughout, e.g. c(NaOH) = [NaOH], when referring to
concentrations.
3.1.2.5 Phenolphthalein, indicator solution.
Dissolve 0,7g of phenolphthalein in 100ml of ethanol.
3.1.3 Apparatus
Standard laboratory apparatus, plus the following:
3.1.3.1 Burette, 50ml capacity, for the sodium hydroxide solution (3.1.2.4).
3.1.3.2 Pipette, 30ml capacity, for the acid solution (3.1.2.2).
3.1.3.3 Pipette, 25ml capacity, for the potassium hydroxide solution (3.1.2.3).
3.1.3.4 Test tube, 50ml capacity, for the xylene (3.1.2.1).
3.1.3.5 Flask, up to 300ml capacity, with stopper.
3.1.3.6 Dropping bottle, for the phenolphthalein indicator solution (3.1.2.5).
3.1.3.7 Reflux condenser, at least 500ml long, in accordance with ISO 4799.
3.1.3.8 Heating equipment: sand bath, oil bath or heating jacket, adjustable to 200°C.
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ISO
ISO 8985:1998(E)
3.1.3.9 Analytical balance, with an accuracy of 0,1mg.
3.1.4 Procedure
3.1.4.1 Determination
3.1.4.1.1 Weigh a quantity of dry polymer as shown in table 1 into the flask (3.1.3.5) to the nearest
0,1mg. The mass of each sample particle shall be less than approx. 0,05g.
Table 1 – Guide to the mass of the sample to be used
Assumed vinyl acetate content, w(VAC) Approximate mass of test portion
% g
w(VAC) ≤ 10
0,5
10 < w(VAC) ≤ 20
0,3
20 < w(VAC) ≤ 40
0,2
40 < w(VAC)
When analysing an unknown sample, first carry out a preliminary test under conditions which are valid for
a copolymer containing 20% to 40% VAC.
3.1.4.1.2 Add 50ml of xylene (3.1.2.1) to the contents of the flask and 25ml of potassium hydroxide
(3.1.2.3), using the pipette (3.1.3.3). Heat the flask, topped with the reflux condenser (3.1.3.7), for 2 hours
using the heating apparatus. After hydrolysis, remove the flask from the heating apparatus and allow to
cool to ambient temperature. Add 30ml of sulfuric or hydrochloric acid (3.1.2.2), using the pipette
(3.1.3.2), stopper the flask and shake vigorously. Add several drops of phenolphthalein solution (3.1.2.5)
and titrate the excess acid with standard sodium hydroxide solution (3.1.2.4), shaking the flask during the
titration.
3.1.4.2  Blank test
Carry out a blank test in parallel with the determination, following the same procedure and using the same
reagents but omitting the test portion.
3.1.5 Expression of results
3.1.5.1 The vinyl acetate content w(VAC), expressed as a percentage by mass, is given by the formula:
8,609 v− v c
()
w VAC=
()
m
where
ν is the volume, in millilitres, of sodium hydroxide solution used for the determination;
ν is the volume, in millilitres, of sodium hydroxide solution used for the blank test;
c is the actual concentration, expressed in moles per litre, of the sodium hydroxide solution used
for the titration;
m is the mass, in grams, of the test portion (see 3.1.4.1.1).
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ISO 8985:1998(E) ISO
3.1.5.2 Carry out two determinations. If the results differ by more than 1%, discard them and run the
determinations again. Report the arithmetic mean of the two determinations.
3.1.6 Test report
The test report shall contain the following information:
a) a reference to this International Standard and the method used;
b) all details necessary for the complete identification of the sample;
c) the result, expressed in accordance with 3.1.5.2.
3.2 Reference method 2: Saponification and potentiometric titration
3.2.1 Principle
A test portion is dissolved in a mixture of xylene and hexan-1-ol and the acetate groups are hydrolysed
with alcoholic potassium hydroxide solution. Acetone is added to prevent copolymer precipitation. The
excess alkali is titrated with standard hydrochloric acid using a potentiometric titrimeter.
3.2.2 Reagents
During analysis use only reagents of recognized analytical quality and distilled water or water of
equivalent purity.
3.2.2.1  Xylene.
3.2.2.2  Hexan-1-ol.
3.2.2.3  Potassium hydroxide, approx. 28g/l ethanolic solution.
3.2.2.4  Acetone.
3.2.2.5  Hydrochloric acid, standard solution, c(HCl) = 0,3mol/l.
3.2.2.6  Lithium chloride, 40g/l ethanolic solution.
3.2.3 Apparatus
Standard laboratory equipment, plus the following:
3.2.3.1  Potentiometric titrator, with a 10ml capacity burette graduated every 0,02ml, a millivoltmeter
or other suitable type of voltmeter, a glass measurement electrode, a silver/silver chloride reference
electrode and a connecting bridge and beaker filled with an ethanolic solution of lithium chloride
(3.2.2.6). Other types of potentiometric titrator may be used.
3.2.3.2  Test tube, capacity 50ml, for the xylene (3.2.2.1) and the acetone (3.2.2.4).
3.2.3.3  Burette, capacity 5ml, for the potassium hydroxide solution (3.2.2.3).
3.2.3.4  Pipette, capacity 10ml, for the hexan-1-ol (3.2.2.2).
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ISO
ISO 8985:1998(E)
3.2.3.5  Flask, capacity 100ml.
3.2.3.6  Reflux condenser, at least 300mm long, in accordance with ISO 4799.
3.2.3.7  Heating apparatus: sand bath, oil bath or heating jacket, adjustable to approx. 200°C
3.2.3.8  Analytical balance, with an accuracy of 0,1mg.
3.2.3.9  Magnetic stirrer.
3.2.4 Procedure
3.2.4.1 Determination
3.2.4.1.1 Weigh a quantity of dry polymer as shown in table 2 into the flask to the nearest 0,1mg. The
mass of each sample particle shall be less than approx. 0,05g.
Table 2 – Guide to the mass of sample to be used
Assumed vinyl acetate content, w(VAC) Approximate mass of test specimen
% g
w(VAC) ≤ 2
0,5
2 < w(VAC) ≤ 5
0,2
5 < w(VAC) ≤ 30
0,1
30 < w(VAC)
When analysing an unknown sample, first of all carry out a preliminary test under conditions which are
valid for a copolymer containing 5% to 30% vinyl acetate.
3.2.4.1.2 Add 25ml of xylene (3.2.2.1) to the contents of the flask and 10ml of hexan-1-ol (3.2.2.2) and
5ml of potassium hydroxide solution (3.2.2.3). Heat the flask, topped with the reflux condenser (3.2.3.6),
for 30 min., using the heating apparatus (3.2.2.7) set at boiling temperature. After 30 min., remove the
flask from the heating apparatus and allow to cool for 5-6 min., then introduce 35ml of acetone (3.2.2.4)
through the top of the condenser. Remove the condenser and place the flask (if conical) on the magnetic
stirrer (3.2.2.9), otherwise transfer the solution to a beaker first. Immerse the glass electrode (see 3.2.3.1)
and one of the ends of the connecting bridge into the flask or beaker. Immerse the other end of the
connecting bridge and the silver/silver chloride reference electrode (see 3.2.3.1) in the beaker filled with
the ethanolic solution of lithium chloride (3.2.2.6).
Carry out the potentiometric titration immediately, adding standard hydrochloric acid (3.2.2.5) until the
first drop in potential and stirring all the time. When close to the end point, add acid in 0,04ml to 0,06ml
increments.
When the end point is reached, read off the voltage, in millivolts, on the titrator as well as the volume of
hydrochloric acid added.
The end point of the titration is that point at which the greatest variation in potential occurs for a given
increment of acid added. In the event of two such points occurring, take the first value as the end point.
The end point may also be determined graphically.
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ISO 8985:1998(E) ISO
3.2.4.2  Blank test
Carry out a blank test in parallel with the determination, following the same procedure and using the same
reagents but omitting the test portion. Plot the titration curve. The mean value of the peak on the titration
curve is taken as the end point.
3.2.5  Expression of results
3.2.5.1 The vinyl acetate content w(VAC), expressed as a percentage by mass, is given by the formula:
8,609 v− v c
()
w()VAC=
m
where
ν is the volume, in millilitres, of standard hydrochloric acid used for the blank test;
ν is the volume; in millilitres, of standard hydrochloric acid solution used for the determination;
c is the actual concentration, in moles per litre, of the standard hydrochloric acid solution used for the
titration;
m  is the mass, in grams, of the test portion (see 3.2.4.1.1).
3.2.5.2 Carry out two determinations. If the results differ by more than 1%, discard them and run the
determination again. Report the arithmetic mean of the two determinations.
3.2.6  Test report
The test report shall contain the following information:
a) a reference to this International Standard and the method used;
b) all details necessary for complete identification of the sample;
c) the result, expressed in accordance with 3.2.5.2.
3.3 Reference method 3: Measurement of oxygen
3.3.1  Principle
The determination of the oxygen content is carried out using one of the traditional methods of e
...