1.1 本标准涵盖了从液体化合物到硬固体材料的导热电绝缘材料的热阻抗测量和表观导热率计算的测试方法。 1.2 术语“导热性”仅适用于均质材料。导热电绝缘材料通常是非均质的，为了避免混淆，本试验方法使用“表观导热系数”来确定均质和非均质材料的热传导特性。 1.3 以国际单位制表示的数值应视为标准值。 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、健康和环境实践，并确定监管限制的适用性。 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热传递的电绝缘材料的稳态热阻抗。本标准特别适用于测量过薄或机械稳定性不足的试样的热传导特性，以便按照试验方法在试样中放置温度传感器 E1225 . 5.2 本标准规定了理想的热流模式，并规定了平均试样试验温度。这样测量的热阻抗不能直接应用于大多数实际应用中，因为这些应用中不存在所需的均匀、平行热传导条件。 5.3 本标准适用于测量以下材料类型的热阻抗。 5.3.1 I型- 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、糊状物和相变材料。这些材料没有表现出弹性行为或在消除挠度应力后恢复初始形状的趋势。 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。例如凝胶、软橡胶和硬橡胶。这些材料表现出线弹性特性，相对于材料厚度具有显著的挠度。 5.3.3 III型- 具有可忽略挠度的弹性固体。例如陶瓷、金属和某些类型的塑料。 5.4 如果界面热阻非常小（名义上小于1），则可以根据测量的热阻抗和测量的试样厚度计算试样的表观导热系数 %) 与试样的热阻进行比较。 5.4.1 通过排除界面热阻，可以准确测定样品材料的表观导热系数。这是通过测量被测材料不同厚度的热阻抗并绘制热阻抗与厚度的关系来实现的。所得直线斜率的倒数是表观导热系数。零厚度处的截距是两个表面的接触电阻之和。 5.4.2 通过在刚性试样（III型）的试验表面上涂抹热润滑脂或油，可以降低接触电阻。

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).