绝热材料老化 闭孔泡沫塑料热阻的长期变化测定(实验室加速法

[中文适用范围]： 本国际标准规定了两种基于切片和缩放技术的实验室测试方法，以确定闭孔（通常为 90%）多孔塑料材料热阻的长期变化，这些材料含有气体，通过扩散过程影响泡沫随时间变化的特性。 使用热阻测量的标准方法，方法 A 包括在受控环境温度环境下对薄样品进行短时间间隔的定期测量。 随时间相对变化的结果与数学技术结合使用，可得出较大厚度材料的热阻随时间的变化。 方法 B 描述了一种简单的测试，用于确定无表面、闭孔、多孔塑料产品的保守设计寿命值（25 年或更长）。 该方法目前仅限于未饰面的均质材料。 对于该方法，在初级热阻率斜率变化和样品内时间关系小于10%的材料芯和表面的多个样本被认为是均匀的。 一般来说，具有天然表皮或通常在此类产品中发现的密度偏差的产品可以被认为可以接受该技术的测试。 [外文原描述]： This International Standard specifies two laboratory test methods, based on slicing and scaling techniques, to determine the long-term changes in the thermal resistance of closed-cell (normally 90 %) cellular plastic materials that contain gases which, through diffusion processes, affect the properties of a foam with time. Using standard methods for the measurement of thermal resistance, method A consists of periodic measurements performed over a short time interval on thin specimens conditioned in a controlled ambient temperature environment. The results of relative change with time are used in conjunction with a mathematical technique to derive the thermal resistance of greater thicknesses of the material as a function of time. Method B describes a simple test to determine a conservative design life-time value (25 years and longer) for an unfaced, closed-cell, cellular plastic product. This method is limited currently to unfaced homogeneous materials. For this method, multiple specimens of the core and surfaces of materials with variations in the slope of the primary stage thermal resistivity and a time relationship of less than 10 % within a sample are considered to be homogeneous. Generally, products with natural skins or with density deviations normally found with such products may be considered acceptable for test by this technique.