This test method determines the ratio of mass/unit area of any nonwoven fabric. Many properties of nonwovens, including strength, thickness, porosity, tearing strength, and others are influenced by changes in mass/unit area. For this reason, many nonwovens specifications include targets and limits for this property, which may be verified using this procedure. Also, it is a useful procedure to use in controlling production of nonwovens and verifying the property of the material being delivered to the customer.
The procedure in this test method may be used for acceptance testing of commercial shipments, but caution is advised since information about between-laboratory precision is incomplete. Comparative tests in accordance with 5.2.1 are advisable.
5.2.1 In case of a dispute arising from differences in reported test results when using the procedures in this test method for acceptance testing of commercial shipments, the purchaser and the manufacturer should conduct comparative tests to determine if there is a 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 that are as homogeneous as possible and which are from a lot of material of the type in question. The test specimen then should be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using the appropriate Student’t-test and an acceptable probability level chosen by the two parties before testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and the manufacturer must agree to interpret future test results with consideration to the known bias.
