Microcellular long-chain branched polyphenylene oxide (PPO) with excellent comprehensive properties and comprehensive analysis of its dielectric properties

Abstract

High-frequency and high-speed communications impose stringent requirements on low-dielectric materials with exceptional comprehensive properties. The development of dielectric materials with low dielectric constants and low dielectric dissipation factors holds significant value in reducing interconnect delay, power consumption, and crosstalk in high-frequency communication. In this study, polyphenylene oxide (PPO), known for its excellent properties, was chosen as the base material. Modified PPO with a long-chain branched structure was prepared using the multi-epoxy modifier ADR-4468. The increase in molecular weight and the formation of a long-chain branched structure improved the thermal stability, flexural properties, and foamability of PPO. Introduction of low-dielectric air into the material was achieved through supercritical CO2 foaming, resulting in a series of microcellular PPO foams exhibiting low dielectric properties (with a dielectric constant as low as 1.12 and a dielectric dissipation factor as low as 0.000636). Concurrently, the dielectric properties of microcellular PPO foams were examined at 10 GHz, revealing that the foam’s dielectric properties were minimally impacted by the properties of the raw materials. Based on water absorption analysis, an improved equation for calculating the dielectric dissipation factor was proposed, comprehensively analyzing the influencing factors on the foam’s dielectric dissipation factor. The study unveiled that water absorption significantly affects the foam’s dielectric dissipation factor, and under high expansion ratios, water absorption’s impact on the dielectric dissipation factor exceeds that of air introduction. These microcellular PPO foams, possessing excellent comprehensive properties and low dielectric characteristics, hold promise for applications in the realm of high-frequency and high-speed communications.