5.1 This test method is not recommended for acceptance testing of commercial shipments because information on between-laboratory precision is known to be poor.

5.1.1 If there are differences of 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, the test samples to be used are as homogenous as possible, are drawn from the material from which the disparate test results were obtained, and are randomly assigned in equal numbers to each laboratory for testing. Other fabrics with established test values may be used for this purpose. 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 a bias is found, either its cause must be found and corrected, or future test results must be adjusted in consideration of the known bias.

5.2 The measurement of the resistance to abrasion of textile fabrics is very complex. The resistance to abrasion is affected by many factors that include the inherent mechanical properties of the fibers; the dimensions of the fibers; the structure of the yarns; the construction of the fabrics; the type, kind, and amount of treatment added to the fibers, yarns, or fabric; the nature of the abradant; the variable action of the abradant over the specimen area abraded; the tension on the specimen; the pressure between the specimen and the abradant; and the dimensional changes in the specimen.

5.3 The measurement of the relative amount of abrasion can be affected by the method of evaluation and is often influenced by the judgment of the operator. It is recognized that with this test method other means of evaluation besides cycles to rupture and breaking strength have been used by the industry, such as color change, appearance change, and so forth. Experience has shown these to be highly variable parameters and they are not recommended without exact criteria identified in an applicable material specification or contract. Consequently, the criteria of breaking strength and cycles to rupture are the recommended means of evaluation because they are considered the least variable and interlaboratory agreement is likely to be obtained more easily.

5.4 Abrasion tests are subject to variations due to changes in the abradant bar during specific tests. The abradant bar is considered a permanent abradant that uses a hardened metal surface. It is assumed that the abradant will not change appreciably in a specific series of tests, but obviously similar abradants used in different laboratories will not likely change at the same rate due to differences in usage. Permanent abradants may also change due to pickup of treatments or other material from test fabrics and must accordingly be cleaned at frequent intervals. Consequently, depending upon its usage, the abradant bar must be checked periodically against a standard.

5.5 The resistance of textile materials to abrasion as measured by this test method does not include all the factors which account for wear performance or durability in actual use. While the abrasion resistance stated in terms of the number of cycles and durability (defined as the ability to withstand deterioration or wearing out in use, including the effects of abrasion) are frequently related, the relationship varies with different end uses. Different factors may be necessary in any calculation of predicted durability from specific abrasion data.

5.5.1 Laboratory tests may be reliable as an indication of relative end use in cases where the difference in abrasion resistance of various materials is large, but they should not be relied upon where differences in laboratory test findings are small. In general, the results should not be relied upon for prediction of performance during actual wear life for specific end uses unless there are data showing the specific relationship between laboratory abrasion tests and actual wear in the intended end use.

5.6 This test method is useful for pretreating material for subsequent testing for strength or barrier performance.

5.7 The pressure and tension used is varied, depending on the mass and nature of the material and the end-use application. Whenever possible, all materials that are to be compared with each other should be tested under the same pressure and tension.

5.8 When abrasion tests are continued to total destruction, abrasion resistance comparisons are not practical for fabrics having a different mass because the change in abrasion resistance is not directly proportional to the change in the fabric mass.

5.9 All the test methods and instruments that have been developed for abrasion resistance may show a high degree of variability in results obtained by different operators and in different laboratories, however, they represent the methods most widely used in the industry. Because there is a definite need for measuring the relative resistance to abrasion, this test method is one of several standardized test methods that is useful to help minimize the inherent variation that may occur in results.

5.10 These general observations apply to most fabrics, including woven and nonwoven fabrics that are used in automotive, household, and wearing apparel applications.