Lightweight, low temperature fatigue resistant, and low dielectric microcellular polyetheretherketone foams fabricated by microcellular injection molding

In this study, microcellular injection molding with supercritical nitrogen was employed to fabricate polyetheretherketone (PEEK) foams. The results showed that microporous PEEK specimens with weight loss up to 22% (specific strength of 58.16) and a low dielectric constant of 2.29 were achieved successfully. It is demonstrated that the microcellular structures and distribution varied with filling distance, due to the variation of pressure and temperature of melt in the mold cavity. Moreover, the low‐temperature resistance of foamed PEEK specimen was evaluated with ultra‐low temperature cycling test. It is found that foamed PEEK specimens demonstrate the same level of performance under low temperature conditions, which provides potential application in extreme environments. PEEK specimens have dielectric constant fluctuations in the X‐band due to the polarization of the molecular chains. In the PEEK foams, microcellular structure significantly influenced their dielectric properties. The wider cell layer enables higher gas content in PEEK foams, resulting in lower dielectric constant. Furthermore, crystallization can suppress the orientational polarization of molecular chains, and thus higher crystallinity results in a smaller dielectric constant. The lightweight, low‐temperature fatigue‐resistant, low‐dielectric microporous PEEK products have tremendous promise as insulation materials in many applications such as communications and microelectronics.