1.1本规程涵盖了热老化、自然或人工加速风化或化学暴露后热塑性塑料和热固性塑料性能保持指数（PRI）的计算程序。 1.2本规程的目的不是建立进行暴露试验的固定程序，而是提供一组特定程序，用于计算暴露后材料特性的保留指数。具体暴露试验条件的选择取决于被测材料和被测性能。 由用户确定哪些暴露试验条件与所使用的特定材料和使用条件最相关。使用的暴露试验必须根据特定暴露标准中描述的条件进行。 1.3本规程未描述待测试材料的取样程序。适用于被评估材料的标准和规范中描述了这些程序。 1.4用于计算PRI的程序取决于用于表征暴露材料的试验是破坏性的还是非破坏性的。 PRI可用于描述材料经过暴露试验后，在指定温度下塑料的短期机械、电气和其他性能。 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。 笔记 1-没有类似或等效的ISO标准。ISO DIS 11248有很大不同，因为它只适用于热固性树脂。 ====意义和用途====== 本规程确定的性能保持指数（PRI）主要旨在为设计工程师提供材料的相对耐久性性能信息。用户应确保使用适当的采样程序来选择要暴露的样本，以便获得的PRI数据实际上代表正在评估的材料。 获得的PRI取决于所测试的材料、所评估的性能和所使用的暴露条件。即使使用相同的暴露试验，为一种特性获得的PRI也可能与相同材料不同特性的PRI不同。 暴露于环境和热处理组合的塑料可能会发生功能性能变化。任何实验室加速老化程序，尤其是那些仅使用单一应力的程序，可能无法实际表明塑料在实际使用条件下可能发生的变化。该实践提供了一种表示特性变化的方法，作为各种测试中暴露时间的函数。获得的PRI数据最好用于比较同时进行相同暴露试验的材料的性能。 实验室加速试验和室外暴露试验都具有高度的可变性，PRI数据将受到这种可变性的影响。例如，室外暴露的PRI数据可能因暴露位置和进行暴露的时间而异。实验室加速暴露试验的可变性可能导致两个实验室进行假定相同试验的PRI数据存在较大差异。从实验室加速试验中获得的PRI数据不能用于预测暴露于自然风化或实际使用条件下的PRI，除非这两种类型的暴露有足够的数据来进行有效的统计比较。 许多不同的暴露技术可用于提供有关环境应力（如光、热和水）对塑料的影响的信息（见实践） D1435 , F1499 , D2565 , D4329 , D4364 和 D4459号 ; 试验方法 D4674 ; 和ISO 877和ISO 4892）。当需要单独评估热的影响时，应按照惯例进行暴露 D3045 . 当需要评估化学暴露的影响时，应根据试验方法进行暴露 D543 . 有许多因素影响物理性质以及暴露后这些性质的保留。 除所用暴露试验条件的完整描述外，参考本规程的任何报告中应包括以下信息:( 1. )测试材料的完整描述，包括类型、来源、制造商代码、形式和以往历史；( 2. )材料和单个试样的制备方法；( 3. )暴露前后用于样品调节的程序；( 4. )确定物理特性的环境的完整描述（例如，温度和相对湿度）； ( 5. )完整描述用于确定测试物理性能的程序，包括测试样本的速率（如适用）；( 6. )如适用，测试样本的孔隙含量以及用于测量孔隙含量的方法。 笔记 2-本规程的目的不是要求用户泄露有关成分的专有信息。为了避免泄露专有信息，可以使用通用描述来提供有关材料成分的信息。 当使用破坏性试验来确定由于暴露而发生的物理或化学变化或两者兼有时，变化量表示为在指定测试环境（例如温度和湿度）下测试的材料获得的值的函数。 在规定的试验环境中同时测量暴露试样和参考试样。 当使用无损检测来确定由于暴露而发生的物理或化学变化或两者兼有时，变化量表示为暴露前在试样上获得的值的函数。暴露前后的试样性能测量试验应在相同的条件下进行（例如，温度和湿度）。 待测量的性能可在ASTM、ISO或其他适用于被测材料的标准中规定，或通过相关方之间的任何事先协议规定。 如果ASTM、ISO或其他适当标准中没有描述用于测量被评估性能的方法，则测试结果报告中应包括测试方法的描述。 人们认识到，如果不指定制备方法，就无法测试材料。为了在比较试验中具有任何意义，应在相同的加工条件下从同一批次中制备或模制通过这些试验程序进行评估的每种材料的样品，并在所需条件下进行试验之前随机化。 必须认识到，材料的批次差异可能会导致结果的额外差异。 笔记 3-对于具有 甘油三酯 当温度高于环境温度时，自由体积的缓慢崩塌，以及随之而来的机械性能的显著变化，如抗疲劳性、抗冲击性、屈服应力和蒸汽传输等，将在温度低于环境温度时加速 甘油三酯 但当温度高于 甘油三酯 . 因此，在高温下培养 甘油三酯 范围可能不稳定地易受烘箱波动影响。 结果取决于试样的哪一侧暴露在某些测试中。例如，在弯曲试验中，根据试样的暴露表面或未暴露表面是否处于张力下，获得了不同的结果。必须注意确保所有暴露的样本在用于在暴露期间固定样本的测试夹具中具有相同的方向。此外，结果还取决于用于测量被监测特性的过程中试样的方向。 冲击试验尤其如此。在用于测量特性特性的过程中，必须注意确保所有试样在测试夹具中的方向相同。 在继续此实践之前，应参考被测材料的规范。材料规范中涵盖的任何试样制备、调节或尺寸，或其某些组合，以及测试参数应优先于本规程中提及的参数。如果没有材料规范，则本规程中描述的默认条件适用。

1.1 This practice covers procedures for the calculation of a property retention index (PRI) of thermoplastic and thermoset plastics after exposure to thermal aging, natural or artificial accelerated weathering, or chemical exposures. 1.2 This practice is not intended to establish a fixed procedure for conducting the exposure test, but it is intended to provide a set of specific procedures used to calculate the retention index of a characteristic property of the material after it has been exposed. Selection of the specific exposure test conditions depends on the material being tested and the property being measured. It is up to the user to determine which exposure test conditions are most relevant to the specific material and the service condition being used. The exposure test used must be conducted in accordance with conditions described in specific exposure standards. 1.3 This practice does not describe procedures for sampling the materials to be tested. These procedures are described in the standards and specifications applicable to the material being evaluated. 1.4 The procedure used to calculate the PRI depends on whether the test used to characterize the materials being exposed is destructive or nondestructive. The PRI can be useful in describing short-term mechanical, electrical, and other properties of plastics at specified temperatures after the materials have been subjected to an exposure test. 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. Note 1—There is no similar or equivalent ISO standard. ISO DIS 11248 is significantly different since it pertains only to thermosetting resins. ====== Significance And Use ====== The property retention index (PRI) determined by this practice is intended primarily to provide relative durability performance information on materials for design engineers. It is up to the user to ensure that appropriate sampling procedures are used for the selection of specimens to be exposed so that the PRI data obtained is actually representative of the material being evaluated. The PRI obtained depends on the material being tested, property being evaluated, and exposure condition used. A PRI obtained for one property will probably not be the same as the PRI for a different property of the same material, even if the same exposure test is used. Plastics exposed to a combination of environmental and thermal treatments may undergo a change in functional performance. Any laboratory-accelerated aging procedure, especially those that use only a single stress, may not realistically indicate the changes a plastic may undergo in actual use conditions. This practice provides a means for expressing the changes in properties as a function of time exposed in a wide variety of tests. The PRI data obtained is best used for comparing the performance of materials subjected to the same exposure test simultaneously. Both laboratory-accelerated and outdoor exposure testing can be highly variable, and the PRI data will be influenced by this variability. For example, PRI data from outdoor exposures can vary depending on the exposure location and the time of year when the exposure is conducted. Variability in laboratory-accelerated exposure tests can result in large differences in PRI data from two laboratories running supposedly identical tests. PRI data obtained from exposure to laboratory-accelerated tests cannot be used to predict the PRI for exposure to natural weathering or actual use conditions unless there is a sufficient amount of data from both types of exposure to allow valid statistical comparisons. A number of different exposure techniques can be used to provide information on the effects of environmental stresses such as light, heat, and water on plastics (see Practices D1435 , F1499 , D2565 , D4329 , D4364 , and D4459 ; Test Method D4674 ; and ISO 877 and ISO 4892). When it is desirable to evaluate the effects of heat alone, exposures should be conducted in accordance with Practice D3045 . When it is desirable to evaluate the effects of chemical exposures, the exposures should be conducted in accordance with Test Method D543 . There are a number of factors influencing the physical properties and the retention of these properties after exposure. In addition to a complete description of the exposure test conditions used, the following information shall be included in any report referencing this practice: ( 1 ) complete description of the material tested, including the type, source, manufacturer's code number, form, and previous history; ( 2 ) methods of preparation for the material and individual test specimens; ( 3 ) procedure used for specimen conditioning prior to and after exposure; ( 4 ) complete description of the environment in which the physical properties were determined (for example, temperature and relative humidity); ( 5 ) complete description of the procedure used to determine the physical properties tested, including the rate at which specimens were tested, if applicable; ( 6 ) if applicable, void content of the specimens tested and the method used to measure void content. Note 2—It is not the intent of this practice to require users to divulge proprietary information regarding composition. To avoid divulging proprietary information, generic descriptions may be used to provide information on material composition. When destructive tests are used to determine a physical or chemical change, or both, which occurs as a result of exposure, the amount of change is expressed as a function of the value obtained for the material tested at a specified test environment (for example, temperature and humidity). The exposed and reference specimens are measured at the same time in the specified test environment. When nondestructive tests are used to determine a physical or chemical change, or both, which occurs as a result of exposure, the amount of change is expressed as a function of the value obtained on the specimens prior to exposure. Property measurement tests on the specimens before and after exposure shall be conducted at the same conditions (for example, temperature and humidity). The property or properties to be measured may be specified in an ASTM, ISO, or other appropriate standard for the material being tested, or by any prior agreement between interested parties. If the method used to measure the property being evaluated is not described in an ASTM, ISO, or other appropriate standard, a description of the test method shall be included in the report of test results. It is realized that a material cannot be tested without specifying the method of preparation. To have any meaning in comparative testing, specimens of each material being evaluated by these test procedures should be prepared or molded from the same lot under identical processing conditions and randomized prior to testing at the conditions desired. It must be realized that lot-to-lot variation in the material may cause additional variability in results. Note 3—For those plastics with a Tg greater than ambient, the slow collapse of free volume, with attendant significant changes in mechanical properties such as fatigue resistance, impact resistance, yield stress, and vapor transmission, etc. will be accelerated at elevated temperatures below the Tg but will be reversed at temperatures above the Tg . Therefore, incubation at elevated temperatures in the Tg range may be erratically susceptible to oven fluctuation effects. The results depend on which side of the test specimen is exposed with some tests. In bending tests, for example, different results are obtained in accordance with whether the exposed surface or the unexposed surface of the test specimen is placed under tension. Care must be taken to ensure that all specimens being exposed have the same orientation in the test fixture used to hold the specimens during exposure. In addition, the results also depend on the orientation of test specimens during the procedure used to measure the property being monitored. This is especially true with impact tests. During the procedure used to measure the characteristic property, care must be taken to ensure that all specimens are oriented the same way in the test fixture. Before proceeding with this practice, reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, or dimensions, or some combination thereof, and testing parameters covered in the material's specification shall take precedence over those mentioned in this practice. The default conditions described in this practice apply if there are no material specifications.