This study examined the morphological, rheological, viscoelastic, electrical, and microwave attenuation properties (RADAR absorbent and EMI shielding) of cyclo‐olefin copolymer (COC) composites prepared with the melt mixing method by using different amounts of graphite (0‐75 phr). Rheological percolation threshold of the graphite was determined as ∼38 phr. The RL analyses of the composites showed that the composites containing a moderate filler content (45 phr) exhibited the best radar absorption performance. Absorption bandwidth and minimum reflection loss (RL) value for the sample containing 45 phr of graphite were determined as 2.335 GHz (10.165‐12.5 GHz) and −39.89 dB, respectively. Total shielding effectiveness (SE_T) values of the sample including 75 phr of graphite varied in the ranges of 30 to 47.5 dB for the sample thicknesses of 7 mm. The correlation of the microstructural parameters and microwave attenuation properties of the composites indicated that the minimum RL value could be obtained at a filler concentration close to the rheological and electrical percolation thresholds. However, it was also revealed that acceptable shielding effectiveness values for commercial applications could be obtained by the samples with higher filler concentrations than the electrical percolation threshold.

中文翻译：

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石墨填充的环烯烃共聚物复合材料的微波衰减性能和结构性质关系的研究

这项研究研究了通过熔融混合法使用不同量的石墨（0-75 phr）制备的环烯烃共聚物（COC）复合材料的形态，流变，粘弹性，电和微波衰减特性（RADAR吸收剂和EMI屏蔽） 。石墨的流变渗透阈值确定为〜38 phr。复合材料的RL分析表明，含适量填料（45 phr）的复合材料表现出最佳的雷达吸收性能。含有45 phr石墨的样品的吸收带宽和最小反射损耗（RL ）值分别确定为2.335 GHz（10.165-12.5 GHz）和-39.89 dB。总屏蔽效能（SE _T）对于7 mm的样品厚度，包含75 phr石墨的样品的值在30到47.5 dB的范围内变化。复合材料的微结构参数和微波衰减特性的相关性表明，在接近流变和电渗流阈值的填料浓度下，可以获得最小的RL值。但是，还发现，填料浓度高于电渗流阈值的样品可以获得商业应用可接受的屏蔽效果值。