5.1 Test Method D3106 for testing permanent deformation of elastomeric yarns is considered satisfactory for acceptance testing of commercial shipments when there is prior agreement as to the exact value of elongation to be used for testing, since current estimates of between-laboratory precision are acceptable.

5.1.1 If there are differences or practical significance between reported test results for two laboratories (or more) comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, test samples that are as homogeneous as possible, drawn from the material from which the disparate test results were obtained, and randomly assigned in equal numbers to each laboratory for testing. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If bias is found, either its cause must be found and corrected, or future test results for that material must be adjusted in consideration of the known bias.

5.2 Yarns are subjected to long periods of tension resulting in an appreciable amount of stretch during normal use. A portion of the induced stretch may be permanent. The amount of permanent deformation is influenced by the amount of tension, the time the yarn is under tension and the time available for recovery between successive uses.

5.3 For optimum processing of elastomeric yarns, the permanent deformation value should be low or zero.