Abstract Macroencapsulation of phase change material (PCM) is one of the enhancement techniques to maximise heat transfer area between PCM and the surrounding heat transfer fluid (HTF). However, the selection of suitable encapsulation material, that can address the volumetric expansion problem and does not react with the core PCM, while being stable at elevated temperature, possesses a challenge. In this work, the thermo-mechanical characterisation of polymeric material is reported, which can be used for medium temperature (200–350 °C) solar applications. Three materials, such as polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK) and polyether ketone ketone (PEKK) are chosen as an encapsulation material for storing a commercially available organic PCM, A164 in the capsule. Capsules of three materials are fabricated and the mechanical properties of the materials are evaluated after every 10 accelerated thermal cycles near the degradation temperature of the materials to understand their behaviour in extreme conditions. Dimensional and weight analyses of the macro encapsulated capsules is also performed to gauge any change in their physical properties. Thermo-mechanical properties show that the polymers chosen can be used as an encapsulation material for solar applications. Dimensional and weight analysis indicate no significant change in the properties of the polymers. High-temperature stability of these polymers even for extended duration indicates a maximum of 3 wt% change only. The compression test on these materials reveals that the PEKK can be used up to 275 °C with Young’s modulus decreases to 0.4 GPa. These results would form the ground for their applications as PCM-encapsulating materials targeting medium temperature solar applications.

中文翻译：

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PTFE、PEEK、PEKK 作为中温太阳能应用封装材料的热机械特性

摘要 相变材料（PCM）的宏观封装是使相变材料（PCM）与周围传热流体（HTF）之间的传热面积最大化的增强技术之一。然而，选择合适的封装材料，既可以解决体积膨胀问题，又不与核心 PCM 发生反应，同时在高温下保持稳定，这是一个挑战。在这项工作中，报告了聚合物材料的热机械特性，可用于中温（200-350°C）太阳能应用。选择三种材料，例如聚四氟乙烯 (PTFE)、聚醚醚酮 (PEEK) 和聚醚酮酮 (PEKK) 作为封装材料，用于在胶囊中存储市售有机 PCM A164。制造三种材料的胶囊，并在接近材料降解温度的每 10 次加速热循环后评估材料的机械性能，以了解它们在极端条件下的行为。还对宏观封装胶囊进行尺寸和重量分析，以衡量其物理特性的任何变化。热机械性能表明所选择的聚合物可用作太阳能应用的封装材料。尺寸和重量分析表明聚合物的性能没有显着变化。这些聚合物的高温稳定性即使在延长的时间内也显示最大仅 3 wt% 的变化。对这些材料的压缩测试表明，PEKK 可在高达 275 °C 的温度下使用，杨氏模量降低至 0.4 GPa。