1.1本规程涵盖了非金属材料直接暴露在环境中应遵循的程序。当风化试验的发起人由单独的机构进行实际暴露时，必须明确定义试验和对照样品暴露的具体条件，并由各方共同商定。 1.2关于玻璃后面的曝光，请参阅实践 G24集团 . 1.3以国际单位制表示的数值应视为标准。括号中的英寸-磅单位仅供参考。 1.4本规程在技术上等同于ISO 877中描述试样直接暴露于环境的部分。 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和健康实践，并确定监管限制的适用性。 ====意义和用途====== 由于紫外线（UV）辐射、湿润时间、温度、污染物和其他因素的差异，材料在自然暴露中的相对耐久性可能会因暴露位置而大不相同。因此，不能假设单个位置的一次暴露结果将有助于确定不同位置的相对耐久性。建议在不同气候的多个位置进行暴露，这代表了广泛的预期使用条件。 由于年复一年的气候变化，单次暴露试验的结果不能用于预测材料降解的绝对速率。需要几年的重复暴露才能获得 “ 平均的 ” 给定位置的测试结果。 太阳紫外线辐射随时间变化很大。 这可能会导致许多聚合物的表观降解速率存在很大差异。除非材料同时暴露在同一位置，否则不建议比较短期（少于一年）暴露材料的结果。 根据太阳总辐射能或太阳紫外线辐射能定义暴露期可以减少单独暴露结果的可变性。太阳紫外线测量通常使用记录宽带紫外线（例如295至385 nm）或窄带紫外线的仪器进行，如7.2.4和7.2.5所述。太阳辐射测量的一个固有限制是，它们不能反映温度和湿度的影响，这也可能影响降解的速率或类型。 暴露架的设计、样本在暴露架上的位置以及相邻样本的类型或颜色可能会影响样本温度和湿润时间。 为了将这些因素引起的可变性降至最低，建议将试样、对照试样和任何适用的风化标准物质放置在单个试验板上，或放置在暴露期间彼此相邻的试验板上。 强烈建议在任何暴露评估中至少使用一种对照材料。使用时，控制材料应符合术语要求 G113页 ，并且与试样具有相似的成分和结构。最好使用两种控制材料，一种具有相对良好的耐久性，另一种具有相对较差的耐久性。除非另有规定，否则对暴露的每个试验和对照材料至少使用两个复制试样。作为试验一部分的控制材料应用于比较试验材料相对于控制材料的性能。 笔记 -该测试架的详细图纸可从美国材料试验学会国际组织获得，地址:宾夕法尼亚州西康舍霍肯巴尔港100号，邮编:19428。请求附件ADJG0007。 图1典型曝光架

1.1 This practice covers procedures to be followed for direct exposure of nonmetallic materials to the environment. When originators of a weathering test have the actual exposure conducted by a separate agency, the specific conditions for the exposure of test and control specimens must be clearly defined and mutually agreed upon between all parties. 1.2 For exposures behind glass, refer to Practice G24 . 1.3 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only. 1.4 This practice is technically equivalent to the parts of ISO 877 that describe direct exposures of specimens to the environment. 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== The relative durability of materials in natural exposures can be very different depending on the location of the exposure because of differences in ultraviolet (UV) radiation, time of wetness, temperature, pollutants, and other factors. Therefore, it cannot be assumed that results from one exposure in a single location will be useful for determining relative durability in a different location. Exposures in several locations with different climates which represent a broad range of anticipated service conditions are recommended. Because of year-to-year climatological variations, results from a single exposure test cannot be used to predict the absolute rate at which a material degrades. Several years of repeat exposures are needed to get an “ average ” test result for a given location. Solar ultraviolet radiation varies considerably as a function of time of year. This can cause large differences in the apparent rate of degradation in many polymers. Comparing results for materials exposed for short periods (less than one year) is not recommended unless materials are exposed at the same time in the same location. Defining exposure periods in terms of total solar or solar-ultraviolet radiant energy can reduce variability in results from separate exposures. Solar ultraviolet measurements are typically made using instruments which record broadband UV (for example, 295 to 385 nm) or narrow band UV, as described in 7.2.4 and 7.2.5. An inherent limitation in solar-radiation measurements is that they do not reflect the effects of temperature and moisture, which may also influence the rate or type of degradation. The design of the exposure rack, the location of the specimen on the exposure rack, and the type or color of adjacent specimens can affect specimen temperature and time of wetness. In order to minimize variability caused by these factors, it is recommended that test specimens, control specimens, and any applicable weathering reference material be placed on a single test panel or on test panels placed adjacent to each other during exposure. It is strongly recommended that at least one control material be part of any exposure evaluation. When used, the control material shall meet the requirements of Terminology G113 , and be of similar composition and construction compared to test specimens. It is preferable to use two control materials, one with relatively good durability and one with relatively poor durability. Unless otherwise specified, use at least two replicate specimens of each test and control material being exposed. Control materials included as part of a test shall be used for the purpose of comparing the performance of test materials relative to the controls. Note —Detailed drawings of this test rack are available from ASTM International, 100 Barr Harbor Dr., W. Conshohocken, PA 19428. Request Adjunct ADJG0007. FIG. 1 Typical Exposure Rack