ASTM D4776/D4776M-18

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Designation: D4776/D4776M − 10 D4776/D4776M − 18
Standard Test Method for
Adhesion of Tire Cords and Other Reinforcing Cords to
Rubber Compounds by H-Test Procedure
This standard is issued under the fixed designation D4776/D4776M; 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.
1. Scope
1.1 This test method covers the measurement of adhesion of reinforcing cords that are bonded to rubber compounds. This test
method is applicable to textile cord structures from both natural and manmade fibers, other than steel. For adhesion testing of steel
tire cords, refer to Test Method D2229.
1.2 This test method is primarily used to evaluate tire cords, using a suitable tire cord adhesive and a suitable rubber compound.
This test method is also used to evaluate (1) tire cord adhesives, and (2) the process of adhesive reaction on the cord using one
consistent form of tire cord and one consistent rubber compound. This test method may be used to evaluate cords in industrial hose
and belting products and other cord reinforced rubber products.
1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard.
1.4 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.
1.5 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:
D76 Specification for Tensile Testing Machines for Textiles
D123 Terminology Relating to Textiles
D1566 Terminology Relating to Rubber
D2229 Test Method for Adhesion Between Steel Tire Cords and Rubber
D4393 Test Method for Strap Peel Adhesion of Reinforcing Cords or Fabrics to Rubber Compounds
D6477 Terminology Relating to Tire Cord, Bead Wire, Hose Reinforcing Wire, and Fabrics
3. Terminology
3.1 Definitions:
3.1.1 For defintionsdefinitions of terms relating to tire cord, bead wire, hose wire, and tire cord fabrics, refer to Terminology
D6477.
3.1.1.1 The following terms are relevant to this standard: adhesion, adhesion, in tire fabrics, cord, curing, H-test adhesion,
industrial yarn, reinforcing cord, rubber, rubber compound, as used in the manufacture of rubber articles, vulcanization.
3.1.2 For definitions of other terms relating to rubber, refer to Terminology D1566.
3.1.3 For definitions of other textile terms related to textiles, refer to Terminology D123.
This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.19 on Industrial Fibers and Metallic
Reinforcements
Current edition approved Jan. 1, 2010Jan. 1, 2018. Published January 2010February 2018. Originally approved in 1988. Last previous edition approved in 20042010 as
ε1
D4776 – 04D4776 – 10. . DOI: 10.1520/D4776-10.10.1520/D4776-18.
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.
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D4776/D4776M − 18
4. Summary of Test Method
4.1 A cord specimen is sandwiched between two layers of rubber compound test stock in a form resembling an “H,” placed in
a heated mold, and cured at a specified temperature and pressure. The test specimen sandwich is then cut to create an H-test
specimen consisting of a single cord with each end embedded in the center of a tab end of the rubber test block (Fig. 1). The test
specimen is placed in the grips of the tensile tester, and then the grips are separated. The maximum force obtained is the H-test
adhesion force.
5. Significance and Use
5.1 Test Method D4776 for the determination of the H-test adhesion of reinforcing cords to rubber compounds may be used for
the acceptance testing of commercial shipments of reinforcing cords but caution is advised since information about
between-laboratory precision is incomplete. Comparative tests as directed in 5.1.1 may be advisable.
5.1.1 In cases of dispute arising from the differences in reported test results when using Test Method D4776 for acceptance
testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is statistical
bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the
two parties should take a group of test specimens which are as homogeneous as possible and which are from a lot of material of
the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The
average results from the two laboratories should be compared using Student’s t-test for unpaired data and an acceptable probability
level chosen by the two parties before testing begins. If a bias is found, either its cause must be found and corrected or the purchaser
and the supplier must agree to interpret future test results in light of the known bias.
5.2 This test method is used to measure the force required to extract the cord from a rubber compound test block.
5.3 This test method is designed to test the adhesion of textiles that are bonded to rubber compounds. Variables that may
contribute to differences in results of this test method include adhesive type, adhesive application procedure, adhesive cure, fiber
type, construction of cords, rubber type, rubber cure, and rubber thickness.
5.3.1 The deleterious effect of ozone in combination with atmospheric moisture on the ability of adhesives to bond with rubber
requires assiduous protection of cords prior to embedment.
FIG. 1 H-Test Specimen
D4776/D4776M − 18
5.4 The expected range of values which characterize acceptable adhesion can be determined in any cord-rubber combination
with experience. For this reason, the purchaser normally establishes a minimum level of adhesion to be obtained by the supplier
in either the supplier’s laboratory or the purchaser’s laboratory using either the supplier’s standard rubber compound or the
purchaser’s rubber compound.
5.5 Another procedure for testing adhesion of cords to rubber compounds is Test Methods D4393 . This procedure has been used
extensively in the trade for acceptance testing. Results obtained by this method cannot be used interchangeably since there is no
overall correlation between them.
6. Apparatus and Materials
6.1 Tensile Testing Machine—Although a constant-rate-of-extension (CRE) tensile testing machine is preferred, a constant-
rate-of-traverse (CRT type, pendulum type) may be used. The specification and methods of calibration and verification of these
machines shall conform to Specification D76. The testing machine shall be equipped with an autographic recorder (rectilinear
coordinates preferred) or an interface computer. There is a distinct difference between the CRE and CRT type testing machines.
Consequently, they cannot be used interchangeably unless a mathematical correlation has been established and agreed upon by the
purchaser and supplier.
6.2 Curing Press, capable of maintaining a minimum pressure of 3.5 MPa [500 psi] over the total area of the mold surface,
equipped with 300 by 300 mm [12 by 12 in.] platens or larger, and capable of a platen temperature control within 63°C [65°F]
of the temperature specified for curing the rubber compound.
6.3 Molds—The design of the molds shall be as shown in Fig. 2. The dimensions of the test specimen are controlled by the
specifications and tolerances of the mold. The dimensions of the mold (6.40 mm [0.250 in.] embedment) in Fig. 2a shall be used
for cords with a dtex of 1100/2 [denier larger than 1000/2] or less. The dimensions of the mold (9.52 mm [0.375 in.] embedment)
in Fig. 2b shall be used for cords with a dtex larger than 1100/2 [denier larger than 1000/2]. The slot size for each mold shall be
1.17 mm 6 0.13 mm [0.046 in. 6 0.005 in.].
6.4 Specimen Grips—The design of the specimen grips shall be as shown in Fig. 3. Two grips are required.
6.5 Tensioning Masses—The masses may be of the hook type, or designed in such a manner that they can be clamped to the
cord. In any event, the total mass shall be 50 g.
6.6 Sheeted Rubber Compound, (sometimes called skim stock), supported on a non hygroscopic non-hygroscopic backing, such
as a plasticizer-free plastic material. Polyethylene film has been found to be satisfactory. The thickness of the rubber stock required
to fill the mold properly shall be determined by experience. As a guide, the thickness of the rubber stock should be not less than
8 % greater than one-half of the mold cavity depth. In any event, the thickness is agreed upon between the purchaser and supplier.
NOTE 1—The important dimension is shown by an asterisk and shall not be altered. All other dimensions are included as guides and may be altered
if desired.
Dimension mm [in.]
A 1.6 [.06]
B 12.5 [.50]
C 25.0 [1.00]
D 40.0 [1.50]
E 7.0 [.28]
F 14.0 [.56]
G 4.0 [.16]
FIG. 3 Specimen Grips for H-Test
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