1.1 本标准涵盖了从液体化合物到硬固体材料的导热绝缘材料的热阻抗测量和表观热导率计算的测试方法。 1.2 术语“热导率”仅适用于均质材料。导热电绝缘材料通常是不均匀的，为了避免混淆，该测试方法使用“表观热导率”来确定均匀和不均匀材料的热传递特性。 1.3 以SI单位表示的值将被视为标准值。 1.4 本标准并不旨在解决与其使用相关的所有安全性问题（如果有）。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法规限制的适用性。1.5 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》中确立的国际公认的标准化原则制定的。 ======意义和用途====== 5.1 本标准测量用于增强电气和电子应用中传热的电绝缘材料的稳态热阻抗。本标准对于测量样品的热传递特性特别有用，这些样品要么太薄，要么机械稳定性不足，无法如试验方法中那样在样品中放置温度传感器 E1225 . 5.2 该标准规定了理想化的热流模式，并规定了平均样品测试温度。如此测量的热阻抗不能直接应用于不存在这些所需的均匀、平行热传导条件的大多数实际应用。 5.3 该标准可用于测量以下材料类型的热阻抗。 5.3.1 I型- 当施加应力时表现出无限变形的粘性液体。这些包括液体化合物，如润滑脂、糊剂和相变材料。这些材料没有表现出弹性行为的证据，也没有在消除偏转应力后恢复到初始形状的趋势。 5.3.2 II型- 粘弹性固体，其中变形应力最终由内部材料应力平衡，从而限制进一步变形。实例包括凝胶、软橡胶和硬橡胶。这些材料表现出相对于材料厚度具有显著偏转的线弹性性质。5.3.3 III型- 挠度可以忽略不计的弹性固体。例子包括陶瓷、金属和一些类型的塑料。 5.4 如果界面热阻与试样的热阻相比微不足道(标称小于1%)，则能够从测量的热阻抗和测量的试样厚度计算试样的表观热导率。 5.4.1 样品材料的表观热导率能够通过排除界面热阻而精确地确定。这通过测量被测材料的不同厚度的热阻抗并绘制热阻抗与厚度的关系图来实现。所得直线的斜率的倒数是表观热导率。零厚度处的截距是两个表面处的接触电阻之和。 5.4.2 接触电阻能够通过将热润滑脂或油施加到刚性测试样品（III型）的测试表面来降低。

1.1 This standard covers a test method for measurement of thermal impedance and calculation of an apparent thermal conductivity for thermally conductive electrical insulation materials ranging from liquid compounds to hard solid materials. 1.2 The term “thermal conductivity” applies only to homogeneous materials. Thermally conductive electrical insulating materials are usually heterogeneous and to avoid confusion this test method uses “apparent thermal conductivity” for determining thermal transmission properties of both homogeneous and heterogeneous materials. 1.3 The values stated in SI units are to be regarded as standard. 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. 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 This standard measures the steady state thermal impedance of electrical insulating materials used to enhance heat transfer in electrical and electronic applications. This standard is especially useful for measuring thermal transmission properties of specimens that are either too thin or have insufficient mechanical stability to allow placement of temperature sensors in the specimen as in Test Method E1225 . 5.2 This standard imposes an idealized heat flow pattern and specifies an average specimen test temperature. The thermal impedances thus measured cannot be directly applied to most practical applications where these required uniform, parallel heat conduction conditions do not exist. 5.3 This standard is useful for measuring the thermal impedance of the following material types. 5.3.1 Type I— Viscous liquids that exhibit unlimited deformation when a stress is applied. These include liquid compounds such as greases, pastes, and phase change materials. These materials exhibit no evidence of elastic behavior or the tendency to return to initial shape after deflection stresses are removed. 5.3.2 Type II— Viscoelastic solids where stresses of deformation are ultimately balanced by internal material stresses thus limiting further deformation. Examples include gels, soft, and hard rubbers. These materials exhibit linear elastic properties with significant deflection relative to material thickness. 5.3.3 Type III— Elastic solids which exhibit negligible deflection. Examples include ceramics, metals, and some types of plastics. 5.4 The apparent thermal conductivity of a specimen is able to be calculated from the measured thermal impedance and measured specimen thickness if the interfacial thermal resistance is insignificantly small (nominally less than 1 %) compared to the thermal resistance of the specimen. 5.4.1 The apparent thermal conductivity of a sample material is able to be accurately determined by excluding the interfacial thermal resistance. This is accomplished by measuring the thermal impedance of different thicknesses of the material under test and plotting thermal impedance versus thickness. The inverse of the slope of the resulting straight line is the apparent thermal conductivity. The intercept at zero thickness is the sum of the contact resistances at the two surfaces. 5.4.2 The contact resistance is able to be reduced by applying thermal grease or oil to the test surfaces of rigid test specimens (Type III).