ASTM D6576-20

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6576 − 13 D6576 − 20
Standard Specification for
Flexible Cellular Rubber Chemically Blown
This standard is issued under the fixed designation D6576; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This specification establishes requirements for chemically blown cellular rubber.
1.2 In the case of conflict between the provisions of this specification and those of detailed specifications or test methods for
a particular product, the latter shall take precedence.
1.3 Unless specifically stated otherwise, by agreement between the purchaser and the supplier, all test methods shall be
performed in accordance with the test methods specified in this specification.
1.4 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for
information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 There is no known ISO equivalent to this specification.
NOTE 1—This specification was revised using the updated test methods and specifications in the latest version of Specification D1056.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D297 Test Methods for Rubber Products—Chemical Analysis
D471 Test Method for Rubber Property—Effect of Liquids
D635 Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position
D883 Terminology Relating to Plastics
D1055 Specifications for Flexible Cellular Materials—Latex Foam (Withdrawn 2014)
D1056 Specification for Flexible Cellular Materials—Sponge or Expanded Rubber
E176 Terminology of Fire Standards
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Conducting Equivalence Testing in Laboratory Applications
2.2 SAE Standard:
SAE J 1351-1993 Hot Odor Test for Insulation Materials
This specification is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plastics
and Elastomers.
Current edition approved Nov. 15, 2013July 1, 2020. Published December 2013July 2020. Originally approved in 2000. Last previous edition approved in 20072013 as
D6576 - 07.D6576 - 13. DOI: 10.1520/D6576-13.10.1520/D6576-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6576 − 20
2.3 Military Standards/Specifications:
MIL STD 105 Sampling Procedures and Tables for Inspection by Attributes
MIL STD 129 Marking for Shipment and Storage
MIL STD 293 Visual Inspection Guide for Cellular Rubber Items
MIL R 6130C Standard Specification for Flexible Cellular Rubber Chemically Blown
2.4 Federal Standards/Specifications:
PPP-B576 Box, Wood, Cleated, Veneer, Paper Overlaid
PPP-B591 Box, Fiberboard, Wood-Cleated
PPP-B601 Box, Wood, Cleated Plywood
PPP-B621 Box, Wood, Nailed and Lock-Corner
PPP-B636 Box, Shipping, Fiberboard
3. Terminology
3.1 For definitions of technical Terms used in this standard are defined in accordance with Terminology D883terms pertaining
to cellular flexible rubber , unless otherwise specified. For terms relating to precision and bias and associated issues, the terms used
in this specification, refer standard are defined in accordance with Terminology E456to . For terms relating to fire, the terms used
in this standard are defined in accordance with Terminology D883E176.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.2.1 cellular material—material, n—a generic term for materials containing many cells (either open or closed, or both)
dispersed throughout the mass.
3.2.2 closed cell—cell, n—a product whose cells are totally enclosed by its walls and hence not interconnecting with other cells.
3.2.3 open cell—cell, n—a product whose cells are not totally enclosed by its walls and open to the surface, either directly or
by interconnecting with other cells.
4. Classification
4.1 Types—This specification covers two types of cellular rubber designated as follows:
4.1.1 Type I—Open cell (sponge rubber).
4.1.2 Type II—Closed cell (expanded rubber).
4.2 Grades—Both types are divided into three grades designated by the letters A, B, and C added to the roman numeral prefix.
4.2.1 Grade A—Oil- and flame-resistant.
4.2.2 Grade B—No requirements for oil, flame resistance, or low temperature.
4.2.3 Grade C—Low-temperature resistant (oil and flame resistance not required).
4.3 Conditions—Each type and class has been divided into three different conditions. Each condition is based on a specific range
of firmness as expressed by compression deflection as follows:
4.3.1 Condition—Super soft a compression >0 to #13.8 kPa
deflection range of (>0 to #2 psi)
4.3.2 Condition—Soft a compression >13.8 to #34.5 kPa
deflection range of (>2 to #5 psi)
4.3.3 Condition—Soft-medium a compression >34.5 to #62.1 kPa
deflection range of (>5 to #9 psi)
4.3.4 Condition—Medium a compression >62.1 to #89.6 kPa
deflection range of (>9 to #13 psi)
4.3.5 Condition—Medium-firm a compression >89.6 to #117.2 kPa
deflection range of (>13 to #17 psi)
4.3.6 Condition—Firm a compression >117.2 to #172.4 kPa
deflection range of (>17 to #25 psi)
5. Significance and Use
5.1 This specification is a revision of MIL R 6130C retaining most of the MIL R 6130C material designations and property
requirements while conforming to ASTM form and style. It is intended to establish requirements for chemically blown cellular
rubber used by government and industry, and is intended as a direct replacement for MIL R 6130C.
6. Materials and Manufacture
6.1 Materials—The materials shall be homogeneous. Except for the following production allowances:
6.1.1 Tears and edge cracks that do not interfere with specified product yield.
6.1.2 Depression and pock marks not exceeding 1 in.
6.1.3 Splices and butt splices.
Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
D6576 − 20
6.1.4 Laminating sheets to achieve thickness.
6.2 The material shall not include the following:
6.2.1 Cemented, bonded, shredded, or reprocessed cellular rubber.
6.2.2 Grade A cellular rubber shall not contain natural rubber.
6.3 Form—Chemically blown cellular rubber shall be furnished as sheets, rolls, or molded shapes as specified, and shall have
a uniform cell structure, with thin skin or rind surfaces. Cut or split sheets void of skin or rind surfaces are permitted to be furnished
only for Type II material when specified.
6.4 Skin or Rind—The surface formed by contact with the mold shall be considered a skin or rind. It shall be of the same
compound, and vulcanized integrally with the cellular structure. Type I shall have skin or rind. It is acceptable for Type II to have
or not have skin or rind.
6.5 Cut or Split Sheets (Type II Only)—When two or more sheets are derived from one thick sheet, the cut or split sheets shall
not be required to possess a skin or rind on either major surface.
6.6 Surfacing—Cellular rubber shall be backed or surfaced with fabric, adhesive, or other materials, when and as specified in
the contract or order or by applicable drawings.
7. Physical Properties
7.1 The various types and grades of cellular rubber shall conform to the physical properties listed in Table 1 together with any
additional requirements indicated by suffix letters in the grade designations as described in Section 4 and Table 2.
8. Tolerances on Dimensions
8.1 Tolerances on dimensions of flexible cellular rubber materials are given in Table 3.
A
TABLE 1 Physical Properties
Type I Type II
Test Method,
Property Basic Requirements Basic Requirements
Section
(Open Cell) (Closed Cell)
super soft >0 to #13.8 (>0 to #2) >0 to #13.8 (>0 to #2) 11
soft >13.8 to #34.5 (>2 to #5) >13.8 to #34.5 (>2 to #5)
soft-medium >34.5 to #62.1 >34.5 to #62.1
(>5 to #9) (>5 to #9)
Compression deflection, kPa (psi), 25 % medium >62.1 to #89.6 >62.1 to #89.6
deflection (>9 to #13) (>9 to #13)
medium-firm > 89.6 to #117.2 > 89.6 to #117.2
(>13 to #17) (>13 to #17)
firm >117.2 to #172.4 >117.2 to #172.4
(>17 to #25) (>17 to #25)
Low-temperature resistance, flex, 180° bend Grade A –40°C (–40°F) pass pass 12
Grade B –40°C (–40°F) pass pass
Grade C –55°C (–67°F) pass pass
B B
Accelerated aging, % retention of original 25 % all grades and conditions ±20 % ±30 % 13
deflection after 7 days at 158°F
Recovery, min, %, after 50 % deflection all grades and conditions 90 60 14
Flame resistance, max, s Grade A 30 30 15
Grade B not required not required
Grade C not required not required
Shrinkage, max, %, 7 days at 158°F All grades and conditions not required 10 16
Water Absorption, max, % all grades and conditions not required 10 % max for densities 10 lb/ft and 17
under
5 % max for densities over 10 lb/ft
Oil aging, % change in volume, IRM Oil 902 Grade A –15 to +30 –15 to +30 18
Grade B not required not required
Grade C not required not required
Color all grades and conditions as manufactured unless as manufactured unless visual
otherwise specified otherwise specified
A
Unless otherwise specified, the basic requirements listed are for all types, grades, and conditions.
B
If the super-soft grade after aging still falls within the compression deflection requirement of 0 – 13.8 kPa (0 – 2 psi), it shall be considered acceptable even though the
change from original was greater than ±20 % or ±30 %, respectively.
D6576 − 20
TABLE 2 Optional Requirements Added by Suffix Letters
Type I Type II
Test Method
Property Optional Requirements Optional Requirements
Section
(Open Cell) (Closed Cell)
Suffix H: Flexing, max, % set in accordance all grades and conditions 10 10 Appendix X1
with Specification D1055
Suffix O: Odor in accordance with SAE all grades and conditions rating to be determined rating to be determined Appendix X1
J-1351
Suffix W: Density in accordance with Specifi- all grades and conditions density to be determined density to be determined
cation D1056
Suffix Y: Sulfur Content, max, % by weight in all grades and conditions 0.60 0.60 Appendix X1
accordance with Test Methods D297
TABLE 3 Dimensions and Tolerances of Cellular Rubber Products for General Applications
Sponge Rubber
Length and Width
Thickness Dimension, Thickness Tolerance, Length and Width Dimension,
Form Tolerance,
mm (in.) mm (in.)± mm (in.)
mm (in.)±
Sheet and strip 3.2 (0.125) and under 0.4 (0.016) 152 (6) and under 1.6 (0.063)
over 3.2 (0.125) to 12.7 (0.50), incl 0.8 (0.032) over 152 (6) to 457 (18), incl 3.2 (0.125)
over 12.7 (0.50) 1.2 (0.047) over 457 (18) 0.5 %
Molded or special shapes 6.4 (0.250) and under 0.8 (0.032) 6.4 (0.250) and under 0.8 (0.032)
over 6.4 (0.250) to 76.2 (3), incl 1.6 (0.063) over 6.4 (0.250) to 76 (3), incl 1.6 (0.063)
over 76 (3) to 457 (18), incl 3.2 (0.125)
over 457 (18) 0.5 %
Expanded Rubber
Sheet and strip 12.7 (0.50) and under 1.6 (0.063) 152 (6) and under 6.4 (0.250)
over 12.7 (0.50) 2.4 (0.094) over 152 (6) to 305 (12), incl 9.6 (0.375)
over 305 (12) 3 %
Molded or special shapes 3.2 (0.125) to 12.7 (0.50), incl 1.6 (0.063) 152 (6) and under 6.4 (0.250)
over 12.7 (0.50) to 38.1 (1.50), incl 2.4 (0.094) over 152 (6) to 305 (12), incl 9.6 (0.375)
over 38.1 (1.50) to 76.2 (3), incl 3.2 (0.125) over 305 (12) 3 %
8.2 Molded Shapes—Tolerance requirements for molded shapes shall be as specified in drawings, contracts, or by the procuring
activity.
8.3 Sheets and Rolls—Unless otherwise specified, the tolerance requirements for thickness, lengths and width of sheets shall be
as specified in Table 3.
9. Test Methods
9.1 Unless specifically stated otherwise, all test methods shall be in accordance with the test methods specified in Sections 10
– 18.
9.2 Precision and Bias—See Section 19.
10. Test Conditions
10.1 Standard Conditions—Unless otherwise specified herein, conduct the test method at 23 6 2°C (73.4 6 3.6°F) and a
relative humidity of 50 6 10 %.
10.2 Specimen Conditioning—Unless otherwise specified, condition all test specimens at standard conditions for at least 22 h
prior to testing.
11. Compression Deflection
11.1 Test in accordance with Sections 17 to 22 of Specification D1056.
12. Low-Temperature Flex Resistance
12.1 Test in accordance with Sections 57 to 61 of Specification D1056. Exposure temperatures shall be in accordance with Table
4.
13. Accelerated Aging
13.1 Test in accordance with Sections 35 to 41 of Specification D1056.
D6576 − 20
TABLE 4 Low-Temperature Flex-Resistance Temperatures
Type Grade Temperature
I A and B –40 ± 1°C (–40 ± 2°F)
I C –55 ± 1°C (–67± 2°F)
II A and B –40 ± 1°C (–40 ± 2°F)
II C –55 ± 1°C (–67± 2°F)
14. Recovery
14.1 Specimen Size—Round test specimen shall be cut 41.3 6 1 mm (1.625 6 0.04 in.) in diameter. Specimens taken from either
sheets or molded shapes shall have a minimum thickness of 6.4 mm (0.250 in.) and a maximum thickness of 28.6 mm (1.125 in.).
Skin on top face, or bottom face, or both, is allowed. Specimens shall be cut so that opposite edges are parallel. The thickness of
the test specimens is permitted to vary, but shall be measured and stated in the report. Measure the thickness of each test specimen
to 0.0254 mm (0.001 in.).
14.2 Compress the specimen to 50 %50 6 1 % of the original thickness for a period of 46 h 6 30 minutes.
14.3 Remeasure the thickness of each specimen 24 h 6 15 minutes after removal from the compression apparatus.
D6576 − 20
14.4 Calculate the average recovery of three specimens as follows:
B
recovery, %5 3100 (1)
A
where:
A = original thickness, and
B = thickness 24 h 6 15 minutes after removal from apparatus.
14.5 Report—The average recovery of the three specimens to the nearest 0.1 %
14.6 Precision and Bias:
14.6.1 See Section 19.
15. Flame Resistance
15.1 Test in accordance with Test Method D635 with the following exceptions:
15.2 Test three specimens and record average propagation time.Three specimens shall be tested.
15.3 Specimen Size: 7.0 6 1 mm (0.275 6 0.04 in.) thick by 12.7 6 1 mm (0.5 6 0.04 in.) wide by 125 6 5 mm (4.92 6 0.2
in.) in length.
15.4 Clamp the specimen on one end with its longitudinal axis horizontal.
15.5 The blue flame shall be 38 6 2 mm (1.49 6 0.078 in.) in height.
15.6 Apply the flame for 60 6 1 s.
15.7 Remove the flame after 60 6 1 s and record the average propagation time in seconds.
15.8 Report the average propagation time of the three specimens to the nearest second.
16. Shrinkage
16.1 Scope—This test method covers the evaluation of shrinkage of flexible cellular elastomeric materials.
16.2 Significance and Use—This test method provides a relatively simple and short-term evaluation of in-use performance with
regard to shrinkage.
16.3 Apparatus—Air-circulating oven equipped with a control to maintain a temperature of 70 6 1°C2°C (158 6 2°F)3.6°F)
during the test and having an expanded metal shelf, and a steel rule, graduated in millimetres (inches), capable of measuring to
minimum increments of 1.0 mm (0.05 in.).
16.4 Test Specimen—Use three specimens approximately 300 by 75 mm (12 by 3 in.) cut from each of the test samples.
16.5 Procedure—At each of two points, approximately 250 mm (10 in.) apart on the centerline of each specimen, place a
benchmark. Condition the specimen a minimum of 24 h at a temperature of 23 6 2°C (73 6 3.6°F) and measure the distance
between the benchmarks to the nearest 1.0 mm (0.05 in.). Place the specimens on an expanded metal shelf in an oven operating
at a temperature of 70 6 1°C2°C (158 6 2°F).3.6°F). After 7 days 6 2 hours, remove the specimens from the oven, condition
for at least 2 h at 23 6 2°C, and remeasure.
16.6 Calculation—Calculate percent shrinkage as follows:
L 2 L
1 2
change in length, %5 3100 (2)
L
where:
L = original length, and
L = length after oven-aging.
16.7 Report—Report the shrinkage as the average change in length of three specimens between the two benchmarks expressed
as a percentage of the length originally measured.
D6576 − 20
16.8 Precision and Bias:
16.8.1 See Section 19.
17. Water Absorption (Type II Only)
17.1 Test in accordance with Sections 43 to 48 of Specification D1056.
18. Oil Aging
18.1 Determine the volume of specimens. Measure the diameter and thickness to the nearest 0.40 mm (0.015 in.).
18.2 Specimen Size—Round test specimen shall be cut 41.3 6 1 mm (1.625 6 0.04 in.) in diameter. Specimens taken from either
sheets or molded shapes have a minimum thickness of
...