1.1 本试验方法包括使用玻璃态二氧化硅膨胀计测定膨胀系数大于1µm/（m.°C）的塑料材料的线性热膨胀系数。在试验温度和施加的应力下，塑料材料应具有可忽略的蠕变或弹性应变率，或两者兼而有之，只要这些特性会显著影响测量的准确性。 1.1.1 试验方法 E228 应用于-30°C和+30°C以外的温度。 1.1.2 本试验方法不得用于测量膨胀系数非常低（即小于1µm/（m.°C））的材料。对于膨胀系数非常低的材料，建议使用干涉仪或电容技术。 1.1.3 一种常见的替代技术是热机械分析，如试验方法所述 E831 ，这允许在扫描的温度范围内测量该特性。 1.2 塑料的热膨胀由一个可逆的成分组成，其上叠加了由于含水量、固化、增塑剂或溶剂的损失、应力释放、相变和其他因素的变化而导致的长度变化。本试验方法旨在尽可能排除这些因素，以确定线性热膨胀系数。一般来说，不可能完全排除这些因素的影响。因此，这种测试方法只能给出真实热膨胀的近似值。 1.3 以国际单位制表示的值应被视为标准值。括号中的值仅供参考。 1.4 本标准并不旨在解决与其使用相关的所有安全问题（如果有的话）。本标准的使用者有责任在使用前建立适当的安全、健康和环境实践，并确定监管限制的适用性。 注1: 目前还没有与该标准等效的ISO。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 =====意义和用途====== 5.1 温度之间的线性热膨胀系数α T 1. 和 T 2. 对于长度为 L 0 在参考温度下的温度由以下方程式给出: 在哪里？ L 1. 和 L 2. 温度下的试样长度 T 1. 和 T 2. 分别。因此，α是通过将单位长度的线性膨胀除以温度变化而获得的。 5.2 大多数塑料的性质和膨胀计的结构使-30°C至+30°C（-22°F至+86°F）成为塑料线性热膨胀测量的方便温度范围。 该范围涵盖了塑料最常用的温度。当在该温度范围之外进行测试时，或者当特定塑料的线性热膨胀特性在此温度范围内未知时，应特别注意以下因素 1.2 . 注2: 在这种情况下，通过热机械分析进行特殊的初步调查，如《实践》中规定的那样 D4065 为了避免过度的误差，可能需要调整过渡温度的位置。使用膨胀计本身定位相变或转变温度的其他方法可以通过使用小于30°C（86°F）的步长或通过观察试样温度稳定上升期间的膨胀率来覆盖所讨论的温度范围。一旦确定了这样的转变点，就应该确定转变点以下和以上温度范围的单独膨胀系数。 为了规范和比较的目的，应使用-30°C至+30°C（-22°F至+86°F）的范围，前提是已知该范围内不存在过渡。 5.3 在继续进行此测试方法之前，如果合适，请参考与被测材料或产品相关的规范。相关ASTM材料或产品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到的那些。如果没有相关的ASTM规范，则默认条件适用。

1.1 This test method covers determination of the coefficient of linear thermal expansion for plastic materials having coefficients of expansion greater than 1 µm/(m.°C) by use of a vitreous silica dilatometer. At the test temperatures and under the stresses imposed, the plastic materials shall have a negligible creep or elastic strain rate or both, insofar as these properties would significantly affect the accuracy of the measurements. 1.1.1 Test Method E228 shall be used for temperatures other than −30°C and +30°C. 1.1.2 This test method shall not be used for measurements on materials with a very low coefficient of expansion (that is, less than 1 µm/(m.°C)). For materials with a very low coefficient of expansion, interferometer or capacitance techniques are recommended. 1.1.3 A common alternative technique is thermomechanical analysis, as described in Test Method E831 , which permits measurement of this property over a scanned temperature range. 1.2 The thermal expansion of a plastic is composed of a reversible component on which are superimposed changes in length due to changes in moisture content, curing, loss of plasticizer or solvents, release of stresses, phase changes, and other factors. This test method is intended for determining the coefficient of linear thermal expansion under the exclusion of these factors as far as possible. In general, it will not be possible to exclude the effect of these factors completely. For this reason, this test method can be expected to give only an approximation to the true thermal expansion. 1.3 The values stated in SI units are to be regarded as standard. The values in parentheses are for information only. 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, 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. 1.5 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 coefficient of linear thermal expansion, α, between temperatures T 1 and T 2 for a specimen whose length is L 0 at the reference temperature, is given by the following equation: Where L 1 and L 2 are the specimen lengths at temperatures T 1 and T 2 , respectively. Therefore, α is obtained by dividing the linear expansion per unit length by the change in temperature. 5.2 The nature of most plastics and the construction of the dilatometer make −30°C to +30°C (−22°F to +86°F) a convenient temperature range for linear thermal expansion measurements of plastics. This range covers the temperatures in which plastics are most commonly used. When testing outside of this temperature range or when linear thermal expansion characteristics of a particular plastic are not known through this temperature range, particular attention shall be paid to the factors mentioned in 1.2 . Note 2: In such cases, special preliminary investigations by thermo-mechanical analysis, such as that prescribed in Practice D4065 for the location of transition temperatures, may be required to avoid excessive error. Other ways of locating phase changes or transition temperatures using the dilatometer itself may be employed to cover the range of temperatures in question by using smaller steps than 30°C (86°F) or by observing the rate of expansion during a steady rise in temperature of the specimen. Once such a transition point has been located, a separate coefficient of expansion for a temperature range below and above the transition point should be determined. For specification and comparison purposes, the range from −30°C to +30°C (−22°F to +86°F) should be used, provided it is known that no transition exists in this range. 5.3 Before proceeding with this test method, if appropriate, make reference to the specification associated with the material or product being tested. Any test specimen preparation, conditioning, dimensions, or testing parameters, or combination thereof, covered in the relevant ASTM material or product specification shall take precedence over those mentioned in this test method. If there are no relevant ASTM specifications, then the default conditions apply.