ASTM D3939-09

This test method is not considered satisfactory for acceptance testing of commercial shipments of fabrics because the between-laboratory precision of the test method is poor (see 15.1).

If there are differences of practical significance between reported test results for two laboratories (or more), comparative test should be performed to determine if there is a statistical significant difference between them, using competent statistical assistance. As a minimum, use the samples for such a comparative test that are as homogeneous as possible, drawn from the same lot of material as the samples that resulted in disparate results during initial testing and randomly assigned in equal numbers to each laboratory. The test results from the laboratories involved 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 testing for that material must be adjusted in consideration of the statistically significant differences.

This test method may be used for quality control testing of fabrics during manufacturing and product comparisons of different fabrics by manufacturers, retailers, and users. This test method may also be used by researchers to examine the effect of new fibers, yarns, fabric constructions, and finishes on the snagging resistance of fabrics.

This test method may be used to test the snagging resistance of most apparel and home furnishings fabrics. However, a different test method may be needed for different types of fabrics and different end-uses (such as towels, pants, and upholstery) (see 5.3.1).

Some fabrics that may not be suitable for this test method are described in 1.2. Many open construction fabrics can be tested for snagging resistance using AATCC Test Method 65. The snagging resistance of many pile floor coverings can be tested by Test Method D 1335. Test Method D 5362 (Bean Bag) may also be considered as an alternative for testing the snagging resistance of fabrics. This test method does not apply to the ABC Snag Tester.

Since fabric snagging can be affected by laundering or drycleaning, it may be advisable to test the snagging resistance of a fabric before and after laundering or drycleaning.

The snagging resistance of a specific fabric varies with individual wearers and general conditions of use. Therefore, it can be expected that garments of the same fabric will show a fairly wide snagging resistance spectrum after wear and much greater variation in wear than in replicate fabric specimens subjected to controlled laboratory tests. This factor should be considered when adopting levels of acceptability for any specification that includes snagging resistance.

Snags observed in worn garments vary appreciably in number and appearance. The appearance of a snag depends particularly on (1) the degree of color contrast between the snag and the surrounding area of the fabric or (2) the presence of long distortions or long protrusions. These conditions are not evaluated when snagging is rated solely on the number of snags. See Section 13 for a description of color contrast, distortion, and protrusion as used in this test method; and see Figs. 1 through 3 in Test Method D 5362 for pictures of fabric defects due to snagging. Because the overall acceptability of a specific fabric is dependent on both the characteristics of the snags and other factors affecting fabric appearance, it is recommended that fabrics tested in the laboratory be evaluated with regard to the defects that may be observed visually and not rated solely on the number of snags developed. A series of visual rating standards (see 6.2.4) may be set up to provide a basis for the ratings. The visual rating standards are most advantageous when the tested laboratory specimens correlate closely in appearance with fabrics from a wear test, for example, when tested laboratory specimens and fabrics from a wear test show similar color contrasts. In the preceding example, a series of fabrics from the wear test would be a good choice for the fabric standards described in 6.2.4.2.

1.1 This test method determines the snagging resistance of a fabric.

1.2 Studies of fabric snagging have shown that this test method is suitable for a range of woven and knitted fabrics made from textured or untextured filament yarns or spun yarns or combinations of these yarns. ^, This test method is not suitable for (1) open construction fabrics (such as a net) because the points on the mace will snag the felt pad rather than the specimen, (2) very heavy or very stiff fabrics that cannot be made to fit tightly on the drum and felt pad, and (3) tufted or nonwoven fabrics because the apparatus is designed for woven and knitted fabrics.

1.3 If after using this test method it is found to be too severe for your fabrics, an alternative method can be used, such as BS 8479 Textiles: Method for Determination of the Propensity of Fabrics to Snagging and Related Surface Defects - Rotating Chamber Method.

1.4 The values stated in either acceptable metric units or in other units shall be regarded separately as the standard. The values stated in each system may not be exact equivalents; therefore, each system must be used independently of the other, without combining values in any way. In case of referee decisions, the metric units will prevail.

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 and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 7.