1.1本试验方法主要用于在日光照明下对均匀、非荧光、几乎无色透明或几乎白色半透明或不透明塑料的黄度（或黄度变化）进行仪器测量。测量在颗粒上进行，并基于使用分光光度计或色度计获得的三刺激值。 1.2本试验方法适用于塑料颗粒的颜色分析。每种材料都可能具有决定颜色值的独特特性。 1.3本程序概述了确定颜色测量值的方法，例如黄度指数、CIE X、Y、Z和Hunter L、a、b或CIE L*、a*、b*。 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和健康实践，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。 ====意义和用途====== 4.1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，或其组合，应优先于本试验方法中提及的。如果没有材料规范，则默认条件适用。 注释2 — 一些材料，例如聚酰胺（尼龙），在颗粒的生产过程中可以以非常不同的方式冷却。 颗粒冷却的这种变化可能仅导致颗粒中结晶度的不同水平。更多结晶尼龙将比非晶态尼龙更不透明。这将导致颗粒不透明度的差异。颗粒形状与材料的结晶度无关。由于结晶度的不同，颗粒外观的这种变化不会影响最终性能。 附注3 — 本试验方法不适用于一般材料规范。 4.2本试验方法描述了一种用于对颗粒形式的树脂进行颜色比较的技术，该技术快速方便，因为它不需要制备，例如成型或挤压试样。该试验方法仅用于比较具有类似颗粒形状、尺寸、纹理和半透明程度的试样。例如，将半透明的盘状颗粒与半透明的盘状颗粒进行比较，而不是与不透明的矩形颗粒进行比较。 4.3由于变量众多，例如生产变量、方法和颗粒形状和尺寸，树脂颗粒颜色的精确测量不一定与最终铸造、模制或挤压产品的颜色直接相关。 当所有样品的形状和尺寸相似时，颜色测量可用于比较颗粒形式的树脂。 4.4需要一个三位数的三刺激系统来完全准确地量化颜色。本程序中使用的一般方法使用规程E308、试验方法D2244、CIE 1976（X，Y，Z）系统和CIELAB 1976颜色空间中描述的CIE系统测量颜色。 3. 4.5三色刺激测量的单个分量，如CIE Y（亮度）、Hunter L、a、b或CIE L*、a*、b*值或其他有用指标，如黄色指数，可用于描述材料的颜色属性。 本试验方法描述了如何进行这些测量的标准程序。

1.1 This test method is intended primarily for the instrumental measurement of the degree of yellowness (or change of degree of yellowness) under daylight illumination of homogeneous, nonfluorescent, nearly-colorless transparent or nearly-white translucent or opaque plastics. The measurement is made on pellets and based on tristimulus values obtained with a spectrophotometer or colorimeter. 1.2 This test method is applicable to the color analysis of plastic pellets. It is possible that each material will have unique characteristics that determine the color values. 1.3 This procedure outlines a method to determine color measurements, such as Yellowness Index, CIE X, Y, Z, and Hunter L, a, b, or CIE L*, a*, b*. 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 and health practices and determine the applicability of regulatory limitations prior to use. Note 1 — There is no known ISO equivalent to this standard. ====== Significance And Use ====== 4.1 Before proceeding with this test method, make reference should be made to the specification of the material being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or a combination thereof, covered in the materials specification shall take precedence over those mentioned in this test method. If there are no material specifications, then default conditions apply. Note 2 — Some materials, such as polyamide (nylon), can be cooled very differently during the production of the pellets. This variation in the cooling of the pellets can result in different levels of crystallinity in the pellets only. More crystalline nylons will be more opaque than amorphous nylons. This will result in differences in pellet opacity. The pellet shape is independent of the crystallinity of the material. This variation in pellet appearance, due to varying levels of crystallinity, does not affect final properties. Note 3 — This test method should not be used for general material specifications. 4.2 This test method describes a technique useful for making color comparisons of resins in pellet form that is fast and convenient as it does not require preparation, such as molding or extruding specimens. The test method shall be used only to compare specimens of similar pellet shape, size, texture, and degree of translucency. For example, compare translucent disc-shaped pellets to translucent disc-shaped pellets, not with opaque, rectangular shaped pellets. 4.3 Exact measurements of resin pellet color are not necessarily directly related to the color of the final cast, molded or extruded product due to the multitude of variables, such as producing variables, methods, and pellet shape and size. Color measurements can be useful for comparing resins in pellet form when all samples are similar in shape and size. 4.4 A three-number tristimulus system is necessary to quantify color completely and precisely. The general method used in this procedure measures color using the CIE Systems described in Practice E308, Test Method D2244, the CIE 1976 (X, Y, Z) system, and, the CIELAB 1976 color space. 3 4.5 Individual components of the tristimulus measurement such as CIE Y (Luminance), Hunter L, a, b, or CIE L*, a*, b* values or other useful metrics like yellowness index can be used to describe color attributes of materials. This test method describes a standard procedure on how these measurements are made.