GB/T 533-2008 English PDF (GBT533-2008)

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GB/T 533-2008: Rubber, vulcanized or thermoplastic -- Determination of density
GB/T 533-2008
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.060
G 40
GB/T 533-2008 / ISO 2781:2007
Replacing GB/T 533-1991
Rubber, vulcanized or thermoplastic - Determination of
density
(ISO 2781:2007, IDT)
ISSUED ON: JUNE 04, 2008
IMPLEMENTED ON: DECEMBER 01, 2008
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Terms and definitions... 5 
3 Principle ... 6 
4 Equipment ... 6 
5 Specimen ... 6 
6 Time interval between forming and testing ... 7 
7 Conditioning of specimens ... 7 
8 Test temperature ... 7 
9 Procedure ... 7 
10 Representation of results ... 9 
11 Test report ... 10 
Rubber, vulcanized or thermoplastic - Determination of
density
WARNING - Personnel using this national standard shall have practical
experience in formal laboratory work. This standard does not point out all possible
safety problems. The user is responsible for taking appropriate safety and health
measures AND ensuring compliance with the relevant national laws and
regulations.
NOTE - Some substances, including some wastes, may be used or generated,
during the fulfillment of this standard procedure. It shall implement appropriate
documentation on safety work or post-use material destruction, during the
operation, meanwhile ensure that local environmental protection requirements
are met.
1 Scope
This standard specifies two methods for determining the density of solid vulcanized or
thermoplastic rubber.
This standard applies to the control of the quality of rubber compounds AND the
estimation of the amount of rubber compound, which is required to produce rubber
products of known volume.
This standard does not apply to the measurement of the relative density of rubber. The
relative density of rubber refers to the ratio -- of the mass of a certain volume of rubber
to the mass of an equal volume of pure water, at a certain temperature.
2 Terms and definitions
The following terms and definitions apply to this standard.
2.1
Density
The mass of rubber per unit volume, at a certain temperature, which is expressed in
megagrams per cubic meter (Mg/m3).
3 Principle
This standard specifies two test methods: Method A and Method B.
Method A: Use an analytical balance, which has a horizontal span, to measure the mass
of the specimen in air and the mass in water. When the specimen is completely
immersed in water, its mass in water is less than that in air; the reduction in mass is
equal to the mass of the water which is replaced by the specimen; the volume of the
drained water is equal to the volume of the specimen.
Method B: It is only used to test the density of specimens that need to be cut into small
pieces to eliminate voids, such as the test of small hole hoses and density of insulated
cables. The testing equipment is usually a balance and a density bottle.
Note: For convenience, all gravity in this standard is expressed in mass units.
4 Equipment
4.1 Common laboratory equipment
4.2 Analytical balance
The analytical balance shall be accurate to 1 mg.
4.3 Horizontal span
The size of the horizontal span is determined, by the size of the beaker, which is used
to weigh the specimen in water (Method A).
4.4 Beaker
The volume of the beaker is generally 250 cm3 (smaller can be selected, according to
the balance) (Method A).
4.5 Density bottle (Method B)
5 Specimen
5.1 The surface of the specimen shall be smooth. There shall be no cracks and dust. The
mass shall be at least 2.5 g. The shape of the specimen for Method B shall be made into
a suitable sheet (see 9.3).
5.2 At least two specimens shall be made for each sample.
with fabric, the covering fabric on the specimen surface shall be removed completely;
the exposed surface of the rubber shall be polished smooth (see GB/T 2941).
9.2 Method A
Use a filament of suitable length, to hang the specimen (Chapter 5) on the hook of the
balance (4.2), so that the bottom of the specimen is approximately 25 mm above the
horizontal span (4.3). The material of the filament shall neither be soluble in water NOR
absorb water. The mass of the filament can be ignored or weighed separately. If weighed
alone, its mass shall be subtracted from the weighing of the specimen (see Note 1).
First weigh the mass of the specimen in air, accurate to 1 mg. Weigh the mass of the
specimen in water again. Place a beaker (4.4), which contains freshly prepared cooled
distilled or deionized water, at standard laboratory temperature (23 °C ± 2 °C or 27 °C
± 2 °C), on the horizontal span rack. Immerse the specimen (with a weight if necessary,
see Note 2) in water. Remove the air bubbles (see Note 3 and Note 4), which are
attached to the surface of the specimen. Weigh it, accurate to 1 mg. Observe for a few
seconds, until it is sure that the pointer no longer drifts, before reading the result.
Note 1: If filaments, which have a mass less than 0.010 g, are used, such as fine nylon filaments,
their mass can be ignored. However, when the specimen is less than 2.5 g (such as measuring
the density of very small O-rings), ignoring the mass of the filament can lead to erroneous
results; in this case, it needs to be included in the calculation of the final result. If a hanging
wire other than filament is used, its volume and mass must be taken into the calculation of the
final result.
Note 2: If weighing a specimen, which has a density of less than 1.00 Mg/m3, a weight shall be
added. The mass of the weight in water shall be weighed separately. Other liquids other than
distilled water, that do not have any effect on the rubber, can also be selected as the weighing
liquid. In this case, the formula in 10.1 shall be used, to calculate the density value. In the
formula, the density of the weighing liquid is used to replace the density of water.
Note 3: The main source of error:
a) Air bubbles on the surface of the specimen, when weighed in water;
b) Influence of filament's surface tension;
c) The specimen is suspended in water with convection. To minimize this effect, the air
temperature inside the balance shall be kept the same as the water temperature.
Note 4: In order to remove air bubbles on the surface of the specimen, a small amount of
surface-active substances, which are similar to detergents, can be added to distilled water (the
recommended ratio is 1:10000), OR the specimen can be quickly dipped in a suitable liquid,
such as methanol or industrial alcohol; the liquid is easily soluble in water and does not swell
or dissolve with rubber. If the latter method is used to remove bubbles, it shall be ensured that
the residual amount of liquid, on the surface of the specimen, is controlled to a minimum.
9.3 Method B
Weigh the clean and dry density bottle and stopper (4.5), each before and after the
specimen (Chapter 5) is placed. Cut the specimen into small pieces; the exact shape and
size depends on the thickness of the original specimen. The size of the cut pieces shall
be not more than 4 mm in two directions, AND not more than 6 mm in the third direction.
The small pieces shall be as large as possible, within this limit. All cut edges shall be
smooth. At standard laboratory temperature, fill the density bottle, which contains the
specimen, with freshly prepared cooled distilled or deionized water, to remove air
bub...