ISO 28641:2026

International
Standard
ISO 28641
Third edition
Rubber compounding ingredients —
2026-08
Organic chemicals — General test
methods
Ingrédients de mélange du caoutchouc — Produits chimiques
organiques — Méthodes d'essai générales
Reference number
© ISO 2026
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Published in Switzerland
ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 General requirements . 2
5.1 Thermometer .2
5.2 Desiccator.2
6 Sampling . 2
6.1 Apparatus .2
6.2 Sampling method .2
7 Test methods . 2
7.1 Density and relative density .2
7.1.1 General .2
7.1.2 Hydrometer method .3
7.1.3 Pyknometer method .3
7.1.4 Expression of results .5
7.1.5 Test report .6
7.2 Loss on heating . .6
7.2.1 General .6
7.2.2 Method A . . .6
7.2.3 Method B . .7
7.2.4 Precision .9
7.2.5 Method C .9
7.2.6 Expression of results . 12
7.2.7 Test report . 12
7.3 Sieve residue . 13
7.3.1 General . 13
7.3.2 Principle . 13
7.3.3 Reagents . 13
7.3.4 Apparatus . 13
7.3.5 Procedure . 13
7.3.6 Calculation .14
7.3.7 Expression of results .14
7.3.8 Precision .14
7.3.9 Test report .14
7.4 pH of water extract .14
7.4.1 Principle .14
7.4.2 Apparatus . 15
7.4.3 Procedure . 15
7.4.4 Test report .16
7.5 Melting point .16
7.5.1 General .16
7.5.2 Method A1 .16
7.5.3 Method B . .18
7.5.4 Method C .19
7.5.5 Expression of results .21
7.5.6 Precision .21
7.5.7 Test report .21
7.6 Temperature of solidification .21
7.6.1 Principle .21
7.6.2 Apparatus .21
7.6.3 Procedure . 22

iii
7.6.4 Expression of results . 23
7.6.5 Test report .24
7.7 Softening point .24
7.7.1 General .24
7.7.2 Principle .24
7.7.3 Apparatus .24
7.7.4 Procedure . 25
7.7.5 Expression of results . 26
7.7.6 Precision . 26
7.7.7 Test report . 26
7.8 Density of the bulk material . 26
7.8.1 Principle . 26
7.8.2 Method A (constant mass method) . 26
7.8.3 Method B (constant volume method) . 28
7.8.4 Test report . 28
7.9 Ash . 29
7.9.1 Principle . 29
7.9.2 Apparatus . 29
7.9.3 Procedure . 29
7.9.4 Calculation . 29
7.9.5 Expression of results . 30
7.9.6 Precision . 30
7.9.7 Test report . 30
7.10 Refractive index . 30
7.10.1 Principle . 30
7.10.2 Apparatus . 30
7.10.3 Procedure .31
7.10.4 Expression of results .32
7.10.5 Precision .32
7.10.6 Test report .32
Annex A (normative) Verification of accuracy of pH-meter .34
Annex B (normative) Calibration of the pH-meter .38
Annex C (informative) Precision .40
Annex D (informative) Conversion formulae between density and relative density .46
Annex E (normative) Automatic measurement methods of melting point . 47
Bibliography .51

iv
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 3, Raw materials (including latex) for use in the rubber industry.
This third edition cancels and replaces the second edition (ISO 28641:2018), which has been technically
revised.
The main changes are as follows:
— updating of the normative references and bibliography;
— addition of an automatic measurement in melting point (see methods A1, A2 and A3);
— addition of a new method of loss on heating (see method C);
— addition of permission for using an Abbe reflectometer with automatic reading device in refractive
index;
— addition of automatic measurement methods of melting point (methods A2 and A3) in Annex E.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
International Standard ISO 28641:2026(en)
Rubber compounding ingredients — Organic chemicals —
General test methods
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices and to determine
the applicability of any national regulatory conditions prior to use.
1 Scope
This document specifies sampling and test methods for the determination of the general characteristics of
organic chemicals such as accelerators, antidegradants (including wax) and vulcanizing agents (excluding
peroxides).
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
1)
ISO 649-1 , Laboratory glassware — Density hydrometers for general purposes — Part 1: Specification
2)
ISO 649-2:1981 , Laboratory glassware — Density hydrometers for general purposes — Part 2: Test methods
and use
ISO 976:2013, Rubber and plastics — Polymer dispersions and rubber latices — Determination of pH
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 3838, Crude petroleum and liquid or solid petroleum products — Determination of density or relative
density — Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods
ISO 4625-1, Binders for paints and varnishes — Determination of softening point — Part 1: Ring-and-ball method
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
ISO 80000-1:2022, Quantities and units — Part 1: General
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
1) Withdrawn.
2) Withdrawn.
— IEC Electropedia: available at https:// www .electropedia .org/
4 Abbreviated terms
The abbreviations of the chemical names of the organic accelerators, antidegradants and vulcanizing agents
used in this document are in accordance with ISO 6472.
5 General requirements
5.1 Thermometer
Where a thermometer is used, it shall be a solid-stem thermometer meeting the requirements of partial
immersion type with the appropriate accuracy and measuring range according to the intended purpose. It
shall have been calibrated before use with a standard thermometer.
5.2 Desiccator
Where a vacuum desiccator is used, the pressure reduction in the desiccator shall not be more than 2,0 kPa,
unless otherwise specified.
6 Sampling
6.1 Apparatus
The apparatus used for sampling shall be suitable for each test method.
6.2 Sampling method
Carry out sampling in accordance with ISO 15528.
To ensure homogeneity, thoroughly blend at least 250 g of the sample before taking any test portions.
7 Test methods
7.1 Density and relative density
7.1.1 General
Select one of the following two methods for the determination of relative density, depending the nature
of the material under test (hereafter referred to as the “sample”), the quantity available and the accuracy
required:
a) hydrometer method (liquid sample);
b) pyknometer method (liquid or solid sample).
NOTE Relative density is generally measured at 20 °C and expressed as relative density (20 °C/20 °C). It
represents the ratio of the mass of the sample in air at 20 °C to the mass of an equal volume of water in air at the same
temperature.
7.1.2 Hydrometer method
7.1.2.1 Apparatus
7.1.2.1.1 Hydrometer, made of a suitable transparent glass, graduated in either density or relative
density at 20 °C, capable of measuring relative density at 20 °C over the range 0,600 to 2,000 and meeting
the requirements of ISO 649-1. The hydrometer shall have been calibrated before use with a standard
hydrometer and the instrumental error shall be known.
NOTE Annex D provides information about how to correct instrumental errors and how to convert density into
relative density or vice versa.
7.1.2.1.2 Thermometer, as specified in 5.1.
7.1.2.1.3 Hollow cylinder. made of glass, having an inside diameter which is at least 25 mm larger than
the maximum diameter of the hydrometer. The height shall be such that, when the hydrometer comes to
rest, its base is at least 25 mm above the bottom of the cylinder.
7.1.2.1.4 Constant-temperature water bath, capable of maintaining a temperature of (20 ± 0,5) °C.
7.1.2.2 Procedure
a) Put the sample in the cylinder, avoiding the inclusion of air bubbles. Maintain the cylinder in the constant-
temperature water bath. Stir the sample. Monitor the temperature of the sample with the thermometer,
immersing it to the designated mark.
b) Condition the hydrometer at (20 ± 0,5) °C. When the temperature of the sample has reached (20 ± 0,5) °C,
slowly put the conditioned hydrometer into the sample and allow it to come to rest. Then push the
hydrometer into the sample by about two-scale divisions and release it.
c) When the hydrometer has stopped moving and is not in contact with the cylinder wall, read the scale to
half the smallest graduation interval.
For a translucent sample, read the scale at the point corresponding to the plane of intersection of the
sample surface and the stem. Do this by gradually raising the eyes from a level a little below the sample
surface and reading the scale when the elliptical sample surface becomes straight.
For an opaque sample, read the scale at the upper edge of the meniscus of the sample surface and
calculate the equivalent lower-edge value by applying a correction in accordance with Clause 4 of
ISO 649-2:1981.
d) Record the result.
NOTE It is not necessary to make a correction if a hydrometer with a scale designed to be read at the upper edge
of the meniscus is used.
7.1.3 Pyknometer method
7.1.3.1 General
Two procedures are specified: one for liquid samples and one for powder samples.

7.1.3.2 Apparatus
7.1.3.2.1 Warden pyknometer, as specified in ISO 3838, made of glass, with a capacity of about 50 cm
and fitted with a plug and a ground-glass cap as shown in Figure 1.
Key
1 cap
2 plug
3 capillary
Figure 1 — Warden pyknometer
7.1.3.2.2 Constant-temperature water bath, capable of maintaining the bath temperature at
(20 ± 0,5) °C.
7.1.3.2.3 Thermometer, as specified in 5.1.
7.1.3.2.4 Laboratory balance, capable of weighing to the nearest 0,5 mg.
7.1.3.3 Method for liquid samples
7.1.3.3.1 Procedure
a) Weigh the pyknometer (mass m ) to the nearest 0,5 mg. Fill it with water at a temperature slightly
rl0
below 20 °C. Immerse the pyknometer up to its neck in the constant-temperature bath maintained at
(20 ± 0,5) °C.
b) When the pyknometer and its contents have reached the bath temperature, insert the stopper, which
has also been brought to the bath temperature. Take the pyknometer out of the water bath and wipe the
top of the stopper so that it is dry and the meniscus of the water in the capillary is flush with the top of
the stopper.
c) Thoroughly wipe the external surface with, for instance, a clean dry cloth or tissue paper to remove all
moisture and put on the cap.
d) Weigh it (mass m ) to the nearest 0,5 mg.
rl2
e) Empty the pyknometer and dry it thoroughly. Then fill it completely with the sample at a temperature of
approximately 20 °C and immerse it up to its neck in the water bath maintained at (20 ± 0,5) °C.
f) When its temperature has become constant, put in the stopper that has been maintained at the same
temperature as the bottle. Wipe the top of the stopper so that it is dry and the meniscus of the sample in
the capillary is flush with the top of the stopper. Take the pyknometer out of the water bath. Thoroughly
wipe the external surface with, for instance, a clean dry cloth or tissue paper to remove all moisture and
put on the cap.
g) Weigh it (mass m ) to the nearest 0,5 mg.
rl1
7.1.3.3.2 Calculation
Calculate the relative density of the liquid sample using Formula (1):
mm
rl10rl
d  (1)
rl
mm
rl20rl
where
d is the relative density of the sample (at 20 °C/20 °C);
rl
m is the mass of the empty pyknometer, in grams;
rl0
m is the mass of the pyknometer filled with water, in grams;
rl2
m is the mass of the pyknometer filled with sample, in grams.
rl1
7.1.3.4 Method for powder samples
7.1.3.4.1 Procedure
If the sample is soluble in water, use another liquid, such as ethanol, toluene or n-octane to fill the pyknometer.
a) Weigh the pyknometer empty (mass m ) and filled with water (mass m ) as described in 7.1.3.3.1 a)
rp0 rp2
to d).
b) Empty the pyknometer and dry it thoroughly. Then take a test portion of about 4 cm from the sample
that has been dried, brought to a temperature of approximately 20 °C and put it into the pyknometer.
Immerse the pyknometer up to its neck in the water bath maintained at (20 ± 0,5) °C.
c) When its temperature has become constant, put in the stopper that has been maintained at the same
temperature as the bottle. Then take the pyknometer out of the water bath, wipe its external surface
with, for instance, a clean dry cloth or tissue paper to remove all moisture and put on the cap.
d) Weigh it (mass m ) to the nearest 0,5 mg.
rp1
e) Fill the pyknometer containing the test portion with water at approximately 20 °C. Immerse it up to its
neck in the water bath at (20 ± 0,5) °C. When its temperature has become constant, weigh it (mass m )
rp3
to the nearest 0,5 mg, following the same procedure as in c) above.
7.1.3.4.2 Calculation
Calculate the relative density of the powder sample using Formula (2):
mm
rp10rp
d  D (2)
rp
mmmm
rp12rp rp03rp
where
d is the relative density of the sample (at 20 °C/20 °C);
rp
m is the mass of the empty pyknometer, in grams;
rp0
m is the mass of the pyknometer filled with water or the liquid used, in grams;
rp2
m is the mass of pyknometer plus test portion, in grams;
rp1
m is the mass of pyknometer plus test portion and water or the liquid used, in grams;
rp3
D is the relative density of water or the liquid used.
7.1.4 Expression of results
Round the result, to four decimal places, in accordance with ISO 80000-1:2022, Clause B.2.

7.1.5 Test report
The test report shall include the following information:
a) all details necessary for the identification of the sample;
b) a reference to this document, i.e. ISO 28641:2026;
c) the test method used (7.1.2 or 7.1.3);
d) the test temperature (20 °C);
e) the size of the test portion;
f) the laboratory temperature and humidity;
g) the test result;
h) any operation not included in this document as well as any unusual features noted during the
determination;
i) the date of the test.
7.2 Loss on heating
7.2.1 General
Use one of the following three methods:
— method A, in which the loss in mass of the sample when heated at 70 °C is regarded as the loss on heating;
— method B, in which the heating conditions (temperature, time) are selected from Tables 1 and 2 and the
loss in mass of the sample when heated under these conditions is regarded as the loss on heating;
— method C, in which the loss in mass of the sample is automatically and rapidly measured using an
infrared drying automatic analyser. This method can be substituted for either method A or B by setting
conditions based on the results of methods A or B. Method C consists of method C1 and method C2.
7.2.2 Method A
7.2.2.1 Apparatus
7.2.2.1.1 Weighing bottle, low form.
7.2.2.1.2 Forced-air convention oven, capable of maintaining the temperature at (70 ± 2) °C.
7.2.2.1.3 Analytical balance, accurate to within ±0,1 mg.
7.2.2.1.4 Desiccator.
7.2.2.2 Procedure
a) Dry a clean weighing bottle (7.2.2.1.1) and stopper (stopper removed) for 30 min in an oven (7.2.2.1.2)
maintained at (70 ± 2) °C. Place the bottle and stopper in the desiccator (7.2.2.1.4) and allow them to
cool room temperature. Weigh the bottle with the stopper to the nearest 0,1 mg (m ).
hA0
b) Weigh approximately a test portion of 5 g to 20 g into the weighing bottle, stopper and weigh to the
nearest 0,1 mg (m ).
hA1
c) Place the weighing bottle, containing the test portion, and the stopper (with the stopper removed) in the
oven, which has been equilibrated at 70 °C, for 3 h.
d) After heating, stopper the weighing bottle and transfer it to the desiccator. Allow sufficient time for the
assembly to reach equilibrium at room temperature. Reweigh the bottle to the nearest 0,1 mg (m ).
hA2
e) Repeat the procedure on a second test portion.
7.2.2.3 Calculation
Calculate the value of the loss on heating, W , expressed in per cent with Formula (3):
hA
mm
hA12hA
W  100 (3)
hA
mm
hA10hA
where
m is the mass of weighing bottle and stopper, in grams;
hA0
m is the mass of weighing bottle, stopper, and test portion before heating, in grams;
hA1
m is the mass of weighing bottle, stopper, and test portion after heating, in grams.
hA2
7.2.3 Method B
7.2.3.1 Apparatus
7.2.3.1.1 Weighing bottle, squat form, 30 mm in height and 60 mm in diameter, fitted with a ground-
glass stopper.
7.2.3.1.2 Drying oven, capable of maintaining a temperature selected from the range 35 °C to 110 °C
within ±2 °C.
7.2.3.1.3 Analytical balance, capable of weighing to the nearest 0,1 mg.
7.2.3.1.4 Desiccator.
7.2.3.2 Procedure
a) Dry the clean weighing bottle and the stopper in the drying oven. Allow them to cool to room
temperature in the desiccator. Weigh the weighing bottle with the stopper to the nearest 0,1 mg. Record
the mass (m ).
hB0
b) Take a test portion of between 3 g and 5 g from the sample and put it into the weighing bottle. Insert the
stopper and weigh the bottle to the nearest 0,1 mg. Record the mass (m ).
hB1
c) Place the weighing bottle in the drying oven. Remove the stopper and place it near the bottle. Heat
under the conditions specified in Table 1 (for accelerators and vulcanizing agents) or Table 2 (for
antidegradants). After heating, transfer the weighing bottle and stopper to the desiccator and leave
them to reach equilibrium at room temperature. Weigh the weighing bottle and stopper to the nearest
0,1 mg. Record the mass (m ).
hB2
d) Repeat procedure a) to c) to give a second result.

Table 1 — Heating temperature and heating time (accelerators and vulcanizing agents)
Accelerator and vulcanizing Temperature Time Accelerator Temperature Time
agent
°C h °C h
3)
BA (CAS Registry Number®
a
CMBT (CAS RN® 37437-20-0)
68411-20-1)
DPG (CAS RN® 102-06-7) CBS (CAS RN® 95-33-0)
DOTG (CAS RN® 97-39-2) TBBS (CAS RN® 95-31-8)
MBT (CAS RN® 149-30-4) DCBS (CAS RN® 4979-32-2)
MBTS (CAS RN® 120-78-5) TETD (CAS RN® 97-77-8)
100 ± 2 2
ZMBT (CAS RN® 155-04-4) DPTH (CAS RN® 971-15-3)
55 ± 2 3
ZDMC (CAS RN® 137-30-4) DPTT (CAS RN® 120-54-7)
ZDEC (CAS RN®14324-55-1) ZDBC (CAS RN®136-23-2)
CuDMC (CAS RN®137-29-1) TeDEC (CAS RN®20941-65-5)
ZEPC (CAS RN® 14634-93-6) DETU (CAS RN® 105-55-5)
b
FeDMC (CAS RN® 14484-64-1) DBTU (CAS RN® 109-46-6)
c
ETU (CAS RN® 96-45-7) TMU (CAS RN® 2489-77-2)
MBSS (CAS RN® 95-32-9) DIBS (CAS RN® 95-29-4) 50 ± 2 3
TMTM (CAS RN® 97-74-5)
80 ± 2 2
TMTD (CAS RN® 137-26-8)
BQD (CAS RN® 105-11-3)
DBQD (CAS RN® 120-52-5)
a
Salt of 2-mercaptobenzothiazole.
b
Ferric dimethyldithiocarbamate.
c
Trimethylthiourea.
Table 2 — Heating temperature and heating time (antidegradants)
Antidegradant Temperature Time Antidegradant Temperature Time
°C h °C h
ADPA (CAS RN® 68412-48-6) ETMQ (CAS RN® 91-53-2)
SPH (CAS RN® 61788-44-1) AANA (CAS RN® 3568-26-1) 75 ± 2 2
MBI (CAS RN® 583-39-1) PAN (CAS RN® 90-30-2)
ZMBI (CAS RN® 3030-80-6) ODPA (CAS RN® 101-67-7, 68411-
46-1)
100 ± 2 2 70 ± 2 2
o-MBp24 (CAS RN® 88-24-4) SDPA (CAS RN® 68442-68-2)
a
p-BBp14 (CAS RN® 85-60-9) DCD (CAS RN® 10081-67-1)
p-TBp14 (CAS RN® 96-69-5) TMQ (CAS RN® 26780-96-1)
DBHQ (CAS RN® 88-58-4) NDBC (CAS RN® 13927-77-0) 50 ± 2 3
DAHQ (CAS RN® 79-74-3) MBMTB (CAS RN® 119-47-1)
a
4,4′-dicumyldiphenylamine.
7.2.3.3 Calculation
Calculate the value of the loss on heating using Formula (4):
3) CAS Registry Number® is a trademark of the American Chemical Society (ACS). This information is given for the
convenience of users of this document and does not constitute an endorsement by ISO of the product named. Equivalent
products may be used if they can be shown to lead to the same results.

mm
hB12hB
W  100 (4)
hB
mm
hB10hB
where
W is the loss on heating, in per cent;
hB
m is the mass of the weighing bottle and stopper, in grams;
hB0
m is the mass of the weighing bottle, stopper and test portion before heating, in grams;
hB1
m is the mass of the weighing bottle, stopper and test portion after heating, in grams.
hB2
7.2.4 Precision
See Clause C.1.
7.2.5 Method C
7.2.5.1 Principle
A test portion is continuously weighed to constant mass by a thermogravimetric method using an automatic
analyser with infrared drying unit. The loss on heating is calculated as the mass lost during this procedure.
7.2.5.2 Apparatus
Use ordinary laboratory apparatus and an automatic analyser consisting of the following components:
a) an infrared drying unit, a far-infrared drying unit or a near-infrared drying unit;
b) a balance, capable of weighing to the nearest 1 mg;
c) a microprocessor, capable of controlling drying conditions such as the temperature and the drying
endpoint, and of continuously calculating loss on heating as the mass lost during drying.
7.2.5.3 Procedure
7.2.5.3.1 General
Either method C1 (which uses a pre-defined drying time) or method C2 (in which drying ends when the
mass loss rate has decreased to a pre-defined level) can be chosen, provided the automatic analyser used
offers the choice. The endpoint (the pre-defined drying time for method C1 or the pre-defined mass loss
rate for method C2) shall be determined for the type or the grade of rubber compounding ingredients to be
analysed.
Examples of test conditions are given in Table 3.
7.2.5.3.2 Determination of endpoints for method C1 and method C2
a) First, the reference sample with a known loss on heating is prepared to carry out the following
procedure 7.2.5.3.2 b) or 7.2.5.3.2 c). If the loss on heating is unknown, measure it in accordance with
the procedure 7.2.5.3.2 d).
b) For method C1, take a test portion of between 2 g and 15 g and weigh it to the nearest 1 mg. Operate
the automatic analyser in accordance with the manufacturer’s instructions, set a drying temperature
(temperature should be below the melting point or decomposition point) and obtain a drying profile
(X axis: time in min, Y axis: loss on heating, in per cent) as shown in Figure 2. From the drying profile,
determine the time at which the value of the loss on heating is equal to the value measured in 7.2.2
(method A) or 7.2.3 (method B). Take this drying time as the pre-defined drying time to be used in
method C1 for this particular type or grade of rubber compounding ingredients.

c) For method C2, take a test portion of between 2 g and 15 g and weigh it to the nearest 1 mg. Operate
the automatic analyser in accordance with the manufacturer’s instructions, set a drying temperature
(temperature should be below the melting point or decomposition point) and obtain a drying profile
(X axis: time, Y axis: mass) as shown in Figure 3. From the drying profile, determine the mass loss rate
at the point on the profile where the value of the loss on heating corresponds to that determined in
7.2.2 (method A) or 7.2.3 (method B). Take this value of the mass loss rate as the endpoint for use in
method C2 for this particular type or grade of rubber compounding ingredients.
NOTE The automatic analyser can be programmed to calculate the value of the loss on heating to determine
the endpoint automatically.
d) In the case of new or unknown substances, first measure the melting point or the decomposition point
of the substance, and then measure the loss on heating at the temperature below whichever is lower
in accordance with 7.2.2 (method A) or the closest condition expected in 7.2.3 (method B). After the
measurement, confirm that there is no change in the state of the test portion such as melting, scorching,
decomposition, etc. If there is any change, lower the temperature condition and measure, then
determine the measurement conditions. Carry out the determination of endpoint for either method C1
or method C2 in accordance with the procedure 7.2.5.3.2 b) or 7.2.5.3.2 c) respectively.
e) The procedure of 7.2.5.3.2 a), 7.2.5.3.2 b), 7.2.5.3.2 c) or 7.2.5.3.2 d) shall be performed individually for
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