【国外标准】 Standard Test Method for Unrestrained Linear Thermal Shrinkage of Plastic Film and Sheeting

4.1 As a result of the manufacturing process, internal stresses may be locked into the film which can be released by heating. The temperature at which shrinkage will occur is related to the processing techniques employed to manufacture the film and may also be related to a phase transition in the base resin. The magnitude of the shrinkage will vary with the temperature of the film.4.2 Shrinkage of a particular material produced by a particular process may be characterized by this test method by making measurements at several temperatures through the shrinkage range of the material.4.3 Following a characterization in a particular case, it is usually sufficient thereafter to measure shrinkage at only one selected temperature for purposes of process or quality control, or both.1.1 This test method covers determination of the degree of unrestrained linear thermal shrinkage at given specimen temperatures of plastic film and sheeting of 0.76 mm (0.030 in.) thickness or less. This test method does not cover shrinkage from loss of solvent in some materials.1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.NOTE 1: This standard and ISO 11501 address the same subject matter, but differ in technical content.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.