1.1 本试验方法 2. 包括在非常低的加载速率（51 mm（2 in.）下测定软塑料薄膜和薄板的抗撕裂性/最小值，用于测量引发撕裂的力。本试验方法的试样几何形状在试样的小面积内产生应力集中。最大应力通常出现在撕裂开始附近，记录为撕裂阻力，单位为牛顿（或磅力）。该方法不适用于在试验过程中发生脆性破坏或最大延伸大于101.6 mm（4 in.）的薄膜或薄片材料。 1.1.1 尽管抗撕裂性可以用试样厚度的牛顿/微米（磅/密耳）表示，但只有在确定了所测试特定材料的相关性时，才建议这样做。 在大多数情况下，不同厚度的薄膜之间的比较是无效的。 注1: 薄膜被任意定义为标称厚度不大于0.25 mm（0.010 in.）的薄板。 1.2 恒定握力分离率试验- 本试验方法采用固定试样的夹具的恒定分离速率。 1.2.1 在本试验方法中，应通过夹持分离测量试样延伸。 1.3 以国际单位制表示的数值应视为标准。括号中给出的值仅供参考。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 注2: 没有已知的ISO等效于本标准。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 塑料薄膜或片材的抗撕裂性是其抗断裂极限的复杂函数。本试验方法中的试样几何形状和试验速度受到控制，以在应力集中的小区域内以远低于使用中通常遇到的速率产生撕裂。经验表明，对于在测试过程中没有脆性破坏或伸长不超过200%的材料，该测试具有最佳的可靠性。 5.2 本试验方法的数据为类似成分塑料试样的抗撕裂性排序提供了比较信息。某些塑料撕裂的实际使用性能可能不一定与本试验方法的数据相关。 5.3 塑料薄膜和薄板的抗撕裂性虽然部分取决于厚度，但与试样厚度没有简单的相关性。因此，以牛顿（或磅力）为单位测量的撕裂力不能在很大的试样厚度范围内归一化，而不会产生材料实际撕裂阻力的误导性数据。本试验方法的数据仅可与样本进行比较，其变化不超过±10 % 根据所有测试样本的标称或平均厚度。因此，撕裂阻力用最大牛顿（或磅）表示- 力）撕裂试样的力。 5.4 塑料薄膜的耐撕裂性可能是一个要求使用本试验方法的规范，但在遵守规范时，应优先进行一些程序修改。因此，建议在使用本试验方法之前参考该材料规范。分类系统表1 D4000 列出了当前存在的ASTM材料标准。

1.1 This test method 2 covers the determination of the tear resistance of flexible plastic film and sheeting at very low rates of loading, 51 mm (2 in.)/min. and is designed to measure the force to initiate tearing. The specimen geometry of this test method produces a stress concentration in a small area of the specimen. The maximum stress, usually found near the onset of tearing, is recorded as the tear resistance in newtons (or pounds-force). The method is not applicable for film or sheeting material where brittle failures occur during testing or where maximum extension is greater than 101.6 mm (4 in.). 1.1.1 Although resistance to tear can be expressed in newtons per microns, (pounds-force per mil) of specimen thickness, this is only advisable where correlation for the particular material being tested has been established. In most cases, comparison between films of dissimilar thickness is not valid. Note 1: Film has been arbitrarily defined as sheeting having nominal thickness not greater than 0.25 mm (0.010 in.). 1.2 Constant-Rate-of-Grip Separation Test— This test method employs a constant rate of separation of the grips holding the test specimen. 1.2.1 Specimen extension shall be measured in this test method by grip separation. 1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information only. 1.4 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 2: There is no known ISO equivalent to this standard. 1.5 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. ====== Significance And Use ====== 5.1 Tear resistance of plastic film or sheeting is a complex function of its ultimate resistance to rupture. The specimen geometry and speed of testing in this test method are controlled to produce tearing in a small area of stress concentration at rates far below those usually encountered in service. Experience has shown the test to have its best reliability for materials which do not have brittle failure or do not elongate greater than two hundred percent during testing. 5.2 The data from this test method furnish comparative information for ranking the tearing resistance of plastic specimens of similar composition. Actual use performance in tearing of some plastics may not necessarily correlate with data from this test method. 5.3 The resistance to tear of plastic film and sheeting, while partly dependent upon thickness, has no simple correlation with specimen thickness. Hence, tearing forces measured in newtons (or pounds-force) cannot be normalized over a wide range of specimen thickness without producing misleading data as to the actual tearing resistance of the material. Data from this test method are comparable only from specimens, which vary by no more than ±10 % from the nominal or average thickness of all specimens tested. Therefore, the tearing resistance is expressed in maximum newtons (or pounds-force) of force to tear the specimen. 5.4 The tear resistance of plastic film may be a specification that requires the use of this test method, but with some procedural modifications that take precedence when adhering to the specification. Therefore, it is advisable to refer to that material specification before using this test method. Table 1 of Classification System D4000 lists the ASTM materials standards that currently exist.