1.1 本试验方法包括通过测量浸没在5.1-cm（2-in.）压力下产生的浮力变化来测定硬质泡沫塑料的吸水率规定浸泡时间96小时的水头。 1.2 本试验方法描述了用于测量浮力变化的两个程序。程序A适用于经历快速吸水或暴露期间体积增加或两者兼有的材料。不具有上述任一特性的材料应通过程序B进行评估。 1.3 对于特定应用，制造商和买方应商定不同于正常96小时试验要求的浸泡时间。 1.4 以国际单位制表示的数值应视为标准。 1.5 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1: 本试验方法等同于ISO 2896 1.6 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 本试验方法的目的是提供一种比较不同泡沫塑料之间相对吸水趋势的方法。它用于规范、产品评估和质量控制。它仅在以下情况下适用于特定的最终用途设计要求:- 使用条件类似于浸泡时间（通常为96小时）和5.1厘米（2英寸）试验方法的水头要求。 注2: ASTM小组委员会D20.22的研究表明，一些泡沫塑料，特别是那些具有开孔或自然间隙的泡沫塑料，在96小时浸泡期后继续吸收大量额外的水。还发现，当暴露在更大的压头下时，某些泡沫塑料的吸水率明显更高，这可能在某些水下装置中遇到。 5.2 本试验方法提供了一种测量因直接接触游离水而产生的吸收的方法。该试验方法的结果不能用于比较泡沫塑料对水蒸气传输和随后在电池内冷凝的阻力。要确定耐水蒸气传输性，请参阅测试方法 E96 . 5.3 吸水率测试受几个重要变量的影响，如果不考虑这些变量，则无法在测试实验室之间达成充分一致。 该测试方法的开发考虑了最严重的可能误差源。看见 注释3- 6. ，了解一些可能的错误来源。 注3: 在某些方法中，由于在获得准确的初始重量之前快速吸水，会遇到错误。本试验方法通过提供用于以这种方式工作的材料的程序A来解释潜在误差。在该程序中，唯一需要的浸没测量是96小时浸没期后进行的最终称重。 注4: 程序A中说明了某些泡沫浸入时体积的增加。该程序适用于表现出此类行为的材料。这是基于浸没期结束时湿试样体积的所有浮力计算得出的。 注5: 通过指定除氧蒸馏水，将附着在浸没试样上并影响最终结果的气泡问题降至最低。 注6: 在计算试样的表观体积时，试样制备过程中打开的表面单元会导致错误。这种误差的程度是单元格大小的函数。该试验方法解释了该误差，因为所有计算均基于真实试样体积。真实试样体积在程序A中确定为测量体积减去切割打开的表面细胞体积。由于真实样品体积是通过直接测量确定的，因此程序B中不需要进行这种校正。 5.4 与试样制备过程中打开的表面细胞相关的体积误差随着细胞尺寸的减小而减小。该试验方法提供了一种选择，即使用平均孔径为0.03 cm或更小的泡沫塑料忽略该变量。对于平均泡孔直径大于0.03-cm的泡沫塑料，在所有有争议的情况下，在确定试样体积时，必须测量泡孔尺寸。 5.5 对于大多数材料，与现场实际安装的产品尺寸相比，试样尺寸较小。如果试样和相应产品的表面体积比不同，则测试结果可能会产生误导。 5.6 在大多数情况下，保水性是一种次要性能特征，对主要特性有影响，例如热性能、表面水分积聚、电解质局部收集、尺寸稳定性等。 5.7 在继续进行本试验方法之前，应参考被测材料的规范。材料规范中涵盖的任何试样制备、调节、尺寸或测试参数应优先于本试验方法中提及的参数。如果没有材料规范，则本标准中的默认条件应适用。

1.1 This test method covers the determination of the water absorption of rigid cellular plastics by measuring the change in buoyant force resulting from immersion under a 5.1-cm (2-in.) head of water for the specified immersion period of 96 h. 1.2 This test method describes two procedures that shall be used to measure the change in buoyant force. Procedure A shall be used for materials that either experience rapid water absorption or that show an increase in volume during the exposure period, or both. Materials that do not exhibit either of these characteristics shall be evaluated by Procedure B. 1.3 For specific applications, immersion periods varying from the normal 96-h test requirement shall be agreed upon between the manufacturer and the purchaser. 1.4 The values stated in SI units are to be regarded as the standard. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Note 1: This test method is equivalent to ISO 2896. 1.6 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 The purpose of this test method is to provide a means for comparing relative water absorption tendencies between different cellular plastics. It is intended for use in specifications, product evaluation, and quality control. It is applicable to specific end-use design requirements only to the extent that the end-use conditions are similar to the immersion period (normally 96 h) and 5.1-cm (2-in.) head requirements of the test method. Note 2: Studies by ASTM Subcommittee D20.22 show that some cellular plastics, particularly those with open cells or natural interstices, continue to absorb additional significant amounts of water beyond the 96-h immersion period. It was also found that water absorption of some cellular plastics is significantly higher when exposed to a greater pressure head, as might be encountered in certain underwater installations. 5.2 This test method provides a means for measuring absorption as a result of direct contact exposure to free water. Results by this test method cannot be used to compare the resistance of cellular plastics to water vapor transmission and subsequent condensation within the cells. To determine resistance to water vapor transmission, see Test Methods E96 . 5.3 Water absorption testing is subject to several important variables, which if not considered, prohibit sufficient agreement among testing laboratories. Development of this test method has taken into account the most serious of the possible sources of error. See Notes 3- 6 , below, for some possible sources of error. Note 3: In some methods, an error is encountered due to a rapid absorption of water before an accurate initial weight can be obtained. This test method accounts for that potential error by providing Procedure A for use with materials that behave in this manner. In this procedure the only submerged measurement required is a final weighing taken after the 96-h immersion period. Note 4: The increase in volume that occurs with some foams when immersed is accounted for in Procedure A. This procedure shall be used for materials that exhibit this type of behavior. This is accounted for by basing all buoyant force calculations on the volume of the wet specimen at the conclusion of the immersion period. Note 5: The problem of air bubbles clinging to the submerged specimen and affecting the end result is minimized by specifying deaerated distilled water. Note 6: Surface cells opened during specimen preparation result in an error when calculating the apparent volume of the test specimen. The degree of this error is a function of cell size. This test method accounts for this error in that all calculations are based on the true specimen volume. The true specimen volume is determined in Procedure A as the measured volume minus the volume of surface cells opened by cutting. This correction is not required in Procedure B since the true specimen volume is determined by direct measurement. 5.4 The volume error associated with surface cells opened during specimen preparation decreases as the cell size decreases. This test method provides the option to ignore this variable with cellular plastics that have an average cell diameter of 0.03 cm or less. For cellular plastics having greater than 0.03-cm average cell diameter and in all cases of dispute, measurement of cell size shall be mandatory in determining the specimen volume. 5.5 For most materials, the size of the test specimens is small compared with the size of the products actually installed in the field. If the surface-to-volume ratios for the test specimens and the corresponding products are different, it is possible that the test results will be misleading. 5.6 In most cases water retention is a secondary performance characteristic that has an influence on a primary characteristic, such as thermal performance, surface accumulation of moisture, localized collection of electrolytes, dimensional stability, etc. 5.7 Before proceeding with this test method, reference shall be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters covered in the material specification shall take precedence over those mentioned in this test method. If there are no material specifications, then the default conditions in this standard shall apply.