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.

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.

This test method is used to measure the force required to extract the cord from a rubber compound test block.

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.

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.

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.

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.