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UDC 678.073 : 620.192.2
IS0
IN TE RN AT1 ON A L O RG A N I Z AT I O N FOR STAND AR D IZ AT1 ON
IS0 RECOMMENDATION
R 306
PLASTl CS
DETERMINATION OF THE VICAT SOFTENING TEMPERATURE
OF THERMOPLASTICS
2nd EDITION
October 1968
This second edition supersedes the first edition
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 306, Determination of the Vieat softeningpoint of thermoplastics, was drawn
up by Technical Committee ISO/TC 61, Plastics, the Secretariat of which is held by the United States of America
Standards Institute (USASI).
Work on this question by the TechnicalCommittee began in 1956 and led,in 1959, to the adoption of a Draft
IS0 Recommendation.
In October 1960, this Draft IS0 Recommendation (No. 380) was circulated to aii the IS0 Member Bodies
for enquiry. It was approved by 22 Member Bodies. Two Member Bodies opposed the approval of the Draft : Italy
and U.S.S.R.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Council which decided, in
May 1963, to accept it as an IS0 RECOMMENDATION.
BRIEF HISTORY RELATING TO THE 2nd EDITION
In September 1964, a Draft Revision (No. 750) was circulated to all the IS0 Member Bodies
for enquiry. It was approved, subject to a few modifications of an editorial nature, by the foliowing
Member Bodies :
Argentina Germany Romania
Australia Hungary South Africa, Rep. of
Austria India Spain
Belgium Israel Sweden
Bulgaria Italy Switzerland
Canada
Japan Turkey
Czechoslovakia Korea, Rep. of
U.A.R.
Denmark Netherlands United Kingdom
Finland New Zealand
U.S.A.
France Poland
Yugoslavia
--
One Member Body opposed the approval of the Draft :
U.S.S.R.
The Draft Revision was then submitted by correspondence to the IS0 Council, which decided,
in October 1968, to accept it.
The title of IS0 Recommendation R 306-1963 has been modified as follows : Plastics -
Determination of the Vicat softening temperature of thermoplastics.
This edition (2nd edition) supersedes the first edition of IS0 Recommendation R 306-1963.
-2-
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ISO/R 306-1968 (E)
IS0 Recommendation R 306
October 1968
P LAST I CS
DETERMINATION OF THE VICAT SOFTENING TEMPERATURE
OF THERMOPLASTICS
1. SCOPE
1.1 ïhis IS0 Recommendation describes two methods for the determination of the Vicat softening
temperature of thermoplastics materials under compression:
- method A using a load of 1 kgf;
- method B using a load of 5 kgf.
These two methods are only applicable to thermoplastics, for which they give a measure of the
1.2
temperature at which they start to soften rapidly.
2. PRINCIPLE
Determination of the temperature at which a standard indenter penetrates ,1 mm into the surface of a
plastics test specimen under one of the loads given in clause 1 .l. During the test the temperature is
raised at a uniform rate.
The temperature at 1 mm penetration is quoted as the Vicat softening temperature (VST) in Celsius
degrees.
3. APPARATUS
The apparatus consists essentially of :
3.1 A rod provided with a loud cunying plate, held in a rigid metal frame so that it can move freely
and vertically, the base of the frame serving to support the test specimen under the indenter at
the end of the rod (see Figure, page 7).
3.2 An indenting tip, preferably of hardened steel, 3 mm (1/8 in) long, of circular cross-section,
and area 1.000 k 0.015 mm2 is fixed at the bottom of the rod. The lower surface of the
indenting tip should be square to the axis of the rod and free from burs.
3.3 A micrometer dial gauge (or other suitable measuring instrument), graduated in divisions of
0.01 mm, should be used to measure the penetration of the indenter into the test specimen. The
thrust of the dial gauge, which contributes to the thrust on the test specimen, should be known
and should comply with clause 3.4 below.
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ISO/R 306-1968 (E)
3.4 A load carrying plate should be fitted to the rod (3.1) and a slotted weight adjusted centrally
such that the total thrust applied to the test specimen can be made up to between 1000 gf and
1050 gf for Method A, and to between 5000 gf and 5050 gf for Method B. The combined
masses of the rod, indenter and load carrying plate should not exceed 100 g.
NOTE. - The construction of the apparatus should be such that the micrometer dial gauge reading caused by
differential thermal expansion over the intended temperature range does not exceed 0.02 mm when the test
specimen is replaced by a piece of borosilicate glass or low thermal expansion alloy steel.
It is recommended that the apparatus be constructed of low thermal expansion alloy.
A heating bath, containing a suitable liquid (see Notes 1 and 2 below), should be provided in
3.5
which the apparatus is placed so that the specimen is at least 35 mm (1.5 in) below the surface
of the liquid. An efficient stirrer should be provided. The heating bath should be equipped with
a means of control so that the temperature can be raised at a uniform rate of 50 ? 5 "C per hour
(see Note 3, below).
3.6 A mercury in glass thermometer (or other accurate temperature measuring device), of appro-
priate range, and with graduations at least at each 0.5 OC should be used to measure tempera-
ture. The scale error at any reading should not exceed 0.5 OC.
NOTES
1. Liquid paraffin, transformer oil, glycerol and silicone oils may be suitable liquid heat-transfer media, but
other liquids may be used. In all cases, it should be established that the liquid chosen is stable at the
temperature used and does not affect the materi
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