Different organic peroxides that cure low-k 1,2-PB/SBS/EPDM composites for high-frequency substrate

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.