Different Organic Peroxides that Cure Low‐ k 1, 2‐PB / SBS / EPDM Composites for High‐Frequency Substrate

Abstract Since the advent of 5G network, polymeric low dielectric constant (low‐ k ) materials have been indispensable for high speed and stable signal transmission at microwave frequency. Herein, the low‐ k composites of 1,2‐polybutadiene/styrene‐butadiene‐styrene triblock copolymer/ethylene‐propylene‐dicyclopentadiene (1,2‐PB/SBS/EPDM) were prepared with cured organic peroxide. Two structurally different organic peroxides, namely dicumyl peroxide (DCP) and bis(1‐(tert‐butylperoxy)‐1‐methylethyl)‐benzene (BIPB), were used as free‐radical initiators. The composites with highly efficient initiator—BIPB exhibited considerably enhanced conversion rate, thermal stability, and cross‐link density compared with the DCP system. Furthermore, the increased cross‐link density contributed to dielectric stability over a broad range of frequency (3‐15 GHz) and superior mechanical properties. The cross‐linked composites possessed the typical low polarity group of C─C single bond with suppressed dielectric constant ( D k ) and loss ( D f ). Especially, the average D k of 2.36 and average D f of 0.0054 were obtained for the composite containing 4 part‐by‐weight (pbw) BIPB. This work demonstrated that the 1,2‐PB/SBS/EPDM composite with 4 pbw BIPB is a good candidate for high‐frequency substrate materials.