GB/T 6670-2008 English PDF (GBT6670-2008)

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GB/T 6670-2008: Flexible cellular polymeric materials -- Determination of resilience by ball rebound
GB/T 6670-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.080.01
G 31
Replacing GB/T 6670-1997
Flexible cellular polymeric materials - Determination of
resilience by ball rebound
(ISO 8307:2007, MOD)
ISSUED ON: AUGUST 19, 2008
IMPLEMENTED ON: MAY 01, 2009
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Principle ... 5
5 Apparatus ... 5
6 Test pieces ... 6
7 Number of test pieces ... 7
8 Test conditions ... 7
9 Procedure and expression of results ... 7
10 Test report ... 9
Annex A (informative) Example of electronic measurement procedure ... 10
Annex B (informative) Comparison of clause and sub-clause numbers between this
Standard and ISO 8307:2007 ... 11
Annex C (informative) Technical differences and reasons between this Standard and
ISO 8307:2007 ... 13
Foreword
This Standard adopts ISO 8307:2007 Flexible cellular polymeric materials -
Determination of resilience by ball rebound by modification, and revises GB/T 6670-
1997 Determination of the rebound properties of soft foam plastics.
The comparison table of clause and sub-clause numbers between this Standard and ISO
8307:2007 is shown in Annex B; the main differences and reasons between this
Standard and ISO 8307:2007 are shown in Annex C.
This Standard replaces GB/T 6670-1997 Cellular plastics - Flexible polyurethane foam
- Determination of resilience.
Compared with GB/T 6670-1997, the main changes of this Standard are as follows:
-- CHANGE the name of this Standard to “Flexible cellular polymeric materials -
Determination of resilience by ball rebound”;
-- ADOPT two determination methods, namely method A and method B, in this
Standard.
Annexes A, B and C of this Standard are informative annexes.
This Standard was proposed by China National Light Industry Council.
This Standard shall be under the jurisdiction of National Technical Committee 48 on
Plastic Products of Standardization Administration of China.
This Standard was drafted by Beijing Technology and Business University and
Sinomax Kuka (Zhejiang) Foam Co., Ltd.
Main drafters of this Standard: Wang Xiuxian, Wang Lei, Qian Hongxiang.
This Standard was previously released as GB 6670-1986.
Flexible cellular polymeric materials - Determination of
resilience by ball rebound
1 Scope
This Standard specifies two methods for determining the resilience of flexible cellular
polymeric materials.
This Standard applies to the determination of resilience by ball rebound of flexible
cellular polymeric materials.
2 Normative references
The terms in the following documents become the terms of this Standard by reference
to this Standard. For dated references, all subsequent amendments (not including errata
content) or revisions do not apply to this standard. However, parties to agreements that
are based on this Standard are encouraged to study whether the latest versions of these
documents can be used. For undated references, the latest edition applies to this
Standard.
GB/T 2918-1998, Plastics - Standard atmospheres for conditioning and testing (idt
ISO 291:1997)
3 Terms and definitions
The following terms and definitions are applicable to this Standard.
3.1
open-cell flexible cellular material
flexible cellular material with less than 25% of its cell volume closed
3.2
closed-cell flexible cellular material
flexible cellular material with more than 25% of its cell volume closed
Note: This preflex conditioning is not applicable to closed-cell material as defined
in 3.2.
9.2 Test method A
9.2.1 Carry out the test immediately after conditioning, preferably in the same
atmosphere as was used to condition the test pieces.
9.2.2 Centre the test piece at the base of the tube and adjust the height of the tube so
that zero rebound is 16 mm ± 0.5 mm above the surface of the test piece. Clamp the
tube to make light contact with the test pieces without causing visible compression.
9.2.3 Mount the steel ball on the release mechanism, then drop it and note the maximum
rebound height to the nearest percentage point. If the ball strikes the tube on the drop
or rebound, the value obtained is invalid. This condition is usually due to the tube not
being vertical or to irregularities on the test piece surface. In order to minimize parallax
error, the eye-level of the observer shall be such that the markings on the tube in the
region where the percentage rebound value is read appear as straight lines. Trial drops
are necessary in order to establish the correct eye-level.
9.2.4 At least three rebound values in succession within 1 min shall be obtained on each
of the three test pieces.
9.2.5 For each test piece, determine the median of the three rebound height values. If
any value deviates by more than 20% (one-fifth) of the median value from the median,
make two additional drops and determine the median for all five rebound height values.
Using the median values obtained for the three test pieces, determine the overall median
value as the rebound resilience value of the material.
If automated measurement is employed, the results shall also be expressed to the nearest
integer.
9.3 Test method B
9.3.1 Carry out the test immediately after conditioning in Clause 8, preferably in the
same atmosphere as was used to condition the test pieces.
9.3.2 Place the test piece horizontally on the rebound test apparatus and adjust the drop
height of the bottom of the steel ball from the fixed position to the sample surface to
460 mm.
9.3.3 Carry out tests according to 9.2.3 ~ 9.2.4.
9.3.4 Expression of results: 3 results are measured for each test piece, and the maximum
value is taken from the 3 results. Then the average value of the 3 maximum values is
calculated as the rebound resilience of the test piece.
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