1.1 本实施规程定义了在实施时适用的试验条件 D1435 和 G7/G7M 用于光降解塑料的室外暴露试验。 1.2 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: 没有已知的ISO等效于本标准。 1.3 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====== 4.1 当作为垃圾丢弃时，使用光降解塑料制成的物品会受到日光（尤其是太阳紫外线辐射）、氧气、热量和水的侵蚀。本实践中使用的5°暴露角代表了垃圾降解的典型条件。 4.2 该实践要求根据太阳紫外线辐射确定暴露持续时间。太阳紫外线辐射随位置和时间变化很大。这可能会导致在聚合物中产生指定降解水平所需的时间出现显著差异。达罗 4. 研究表明，当同一批含有铁盐降解剂的聚乙烯在一年中的不同时间暴露在单个位置时，每个分子产生两次平均链断裂所需的时间变化超过130 %. Daro，Zerlaut和Anderson 5. 已经表明，当使用总太阳辐射或太阳紫外线辐射或两者来表征暴露增量时，这种可变性可以显著降低。 4.3 除了日光和太阳紫外线辐射水平的变化外，不同地点之间、不同年份之间或一年内的同一地点的温度和水分应力也存在显著差异。由于这种可变性，本试验的结果不能用于预测光降解塑料降解的绝对速率。该试验的结果可用于比较在同一位置同时暴露的材料的相对降解率。在不同地点多次暴露常见材料（在几年的不同季节）的结果可用于比较特定光降解塑料在每个位置降解的相对速率。 注2: 太阳辐射测量的一个固有局限性是，它们不能反映温度和湿度暴露变化的影响，而温度和湿度暴露往往与太阳辐射一样重要。相同的太阳紫外线辐射增量不一定会在不同暴露位置引起相同的试样特性变化。这种做法的结果必须被视为仅给出降解程度的一般指示，并且应始终根据暴露部位的特征来考虑。 4.4 在无法测量太阳紫外线总辐射的情况下，暴露持续时间可以通过暴露的天数、周数或月数来确定。当使用本规程时，必须在暴露其他被测材料的同时，暴露降解性能已经确定的参考材料。 使用的参考材料必须经所有相关方同意。然后比较在这种同时暴露中每种材料产生指定降解水平的时间。当曝光长度由太阳总辐射或太阳紫外线辐射确定时，使用标准物质也是一种良好的做法。 注3: 参考物质可以是一批在多次暴露后显示出一致结果的物质。无需由公认的标准机构或团体对标准物质的成分或性质进行表征和认证。

1.1 This practice defines test conditions applicable when Practices D1435 and G7/G7M are employed for the outdoor exposure testing of photodegradable plastics. 1.2 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: There is no known ISO equivalent to this standard. 1.3 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 ====== 4.1 When discarded as litter, articles made using photodegradable plastics are subject to attack by daylight (particularly solar-ultraviolet radiation), oxygen, heat, and water. The 5° exposure angle used in this practice represents typical conditions for degradation experienced by litter. 4.2 This practice requires characterization of the duration of exposure in terms of solar-ultraviolet radiation. Solar-ultraviolet radiation varies considerably as a function of location and time of year. This can cause dramatic differences in the time required to produce a specified level of degradation in a polymer. Daro 4 has shown that when the same lot of polyethylene containing an iron-salt prodegradant is exposed at various times of the year in a single location, the time required to produce an average of two chain scissions per molecule varied by over 130 %. Daro, and Zerlaut and Anderson 5 have shown that this variability can be significantly reduced when total solar or solar-ultraviolet radiation, or both, is used to characterize the exposure increments. 4.3 In addition to variations in level of daylight and solar-ultraviolet radiation, there are significant differences in temperature, and moisture stresses between different locations, and between different years, or periods within a single year, at a single location. Because of this variability, results from this test cannot be used to predict the absolute rate at which photodegradable plastics degrade. Results from this test can be used to compare relative rates of degradation for materials exposed at the same time in the same location. Results from multiple exposures of a common lot of material (during different seasons over several years) at different sites can be used to compare the relative rates at which a particular photodegradable plastic will degrade in each location. Note 2: An inherent limitation in solar-radiation measurements is that they do not reflect the effects of variations in temperature and moisture exposure, which often can be as important as solar radiation. The same solar-ultraviolet radiation increment will not necessarily give the same changes in properties of the test specimen in different exposure sites. Results from this practice must be regarded as giving only a general indication of the degree of degradability and should always be considered in terms of characteristics of the exposure site as well. 4.4 Where measurement of total solar-ultraviolet radiation is not possible, exposure duration can be determined by the number of days, weeks, or months exposed. When this practice is used, a reference material whose degradation properties have been well established must be exposed at the same time as the other materials being tested. The reference material used must be agreed upon by all interested parties. The time to produce a specified level of degradation for each material in this simultaneous exposure is then compared. It is also a good practice to use reference materials when exposure length is determined by total solar or solar UV radiant exposure. Note 3: A reference material can be a single lot of material which has shown consistent results after a number of exposures. It is not necessary that the composition or properties of the reference material be characterized and certified by a recognized standards agency or group.