GB/T 6670-2008 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 is applicable to the determination of resilience of flexible cellular polymeric materials.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding any corrigendum), or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the latest editions of the standards indicated below. For undated references, the latest edition of the document referred to applies.
GB/T 2918-1998 Plastics - Standard atmospheres for conditioning and testing (idt ISO 291:1997)
3 Terms and definitions
For the purposes of this standard, the following terms and definitions apply.
3.1
open-cell flexible cellular material
flexible foam material with less than 25 % of its cell volume closed
3.2
closed-cell flexible cellular material
flexible foam material with more than 25 % of its cell volume closed
4 Principle
A steel ball of specified mass and diameter is dropped onto the specimen surface from a fixed height. Measure the rebound height of the steel ball, and calculate the percentage ratio of the rebound height to the drop height.
5 Apparatus
5.1 Method A
5.1.1 Apparatus and main parameters
The ball rebound test apparatus (see Figure 1) shall consist of a 30 mm to 65 mm inside diameter transparent tube, a 16 mm ± 0.5 mm diameter steel ball with a mass of 16.8 g ± 1.5 g, which is released by a magnet or other suitable device. The steel ball falls without rotation and is always centred. The height of the drop is 500 mm ± 0.5 mm. The top of the ball shall be 516 mm above the surface of the test piece. Thus, “zero” rebound shall be the diameter of the ball above the specimen surface.
Measurement errors can arise if the tube is not held in a vertical position, and measurements may be invalid due to contact of the rebounding ball and the inner surface of the tube. Use a spirit level or similar device to ensure that the baseplate is horizontal tube, and the transparent tube and stand are vertical.
5.1.2 Apparatus with manual reading
The scale on the back of the tube shall be graduated in per cent as follows: every 5 % (25 mm) a complete circle shall be scribed and at every 1 % (5 mm) a 120° arc shall be scribed on the tube. The complete circles are an essential part of the apparatus, since they can eliminate parallax error.
5.1.3 Apparatus with automatic reading
A device capable of determining the rebound height of the steel ball by electronic means can, which has been demonstrated to give the same results as the manual-reading apparatus. The rebound height can be calculated from the rebound velocity or the time interval between the first and second contacts of the ball with the foam surface. The apparatus mounted shall indicate a height precision of ±1% (5 mm). For this type of apparatus, the tube does not require graduations (see Annex A for the example of electronic measurement).
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Apparatus
6 Test pieces
7 Number of test pieces
8 Test conditions
9 Procedure and expression of results
10 Test report
Annex A (Informative) Example of electronic measuring
Annex B (Informative) Comparison between this standard and ISO 8307:2007 in terms of clause number
Annex C (Informative) Technical differences between this standard and ISO 8307: 2007 and their justifications
GB/T 6670-2008 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 is applicable to the determination of resilience of flexible cellular polymeric materials.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated reference, subsequent amendments to (excluding any corrigendum), or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the latest editions of the standards indicated below. For undated references, the latest edition of the document referred to applies.
GB/T 2918-1998 Plastics - Standard atmospheres for conditioning and testing (idt ISO 291:1997)
3 Terms and definitions
For the purposes of this standard, the following terms and definitions apply.
3.1
open-cell flexible cellular material
flexible foam material with less than 25 % of its cell volume closed
3.2
closed-cell flexible cellular material
flexible foam material with more than 25 % of its cell volume closed
4 Principle
A steel ball of specified mass and diameter is dropped onto the specimen surface from a fixed height. Measure the rebound height of the steel ball, and calculate the percentage ratio of the rebound height to the drop height.
5 Apparatus
5.1 Method A
5.1.1 Apparatus and main parameters
The ball rebound test apparatus (see Figure 1) shall consist of a 30 mm to 65 mm inside diameter transparent tube, a 16 mm ± 0.5 mm diameter steel ball with a mass of 16.8 g ± 1.5 g, which is released by a magnet or other suitable device. The steel ball falls without rotation and is always centred. The height of the drop is 500 mm ± 0.5 mm. The top of the ball shall be 516 mm above the surface of the test piece. Thus, “zero” rebound shall be the diameter of the ball above the specimen surface.
Measurement errors can arise if the tube is not held in a vertical position, and measurements may be invalid due to contact of the rebounding ball and the inner surface of the tube. Use a spirit level or similar device to ensure that the baseplate is horizontal tube, and the transparent tube and stand are vertical.
5.1.2 Apparatus with manual reading
The scale on the back of the tube shall be graduated in per cent as follows: every 5 % (25 mm) a complete circle shall be scribed and at every 1 % (5 mm) a 120° arc shall be scribed on the tube. The complete circles are an essential part of the apparatus, since they can eliminate parallax error.
5.1.3 Apparatus with automatic reading
A device capable of determining the rebound height of the steel ball by electronic means can, which has been demonstrated to give the same results as the manual-reading apparatus. The rebound height can be calculated from the rebound velocity or the time interval between the first and second contacts of the ball with the foam surface. The apparatus mounted shall indicate a height precision of ±1% (5 mm). For this type of apparatus, the tube does not require graduations (see Annex A for the example of electronic measurement).
Contents of GB/T 6670-2008
Contents
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Apparatus
6 Test pieces
7 Number of test pieces
8 Test conditions
9 Procedure and expression of results
10 Test report
Annex A (Informative) Example of electronic measuring
Annex B (Informative) Comparison between this standard and ISO 8307:2007 in terms of clause number
Annex C (Informative) Technical differences between this standard and ISO 8307: 2007 and their justifications
