Lightweight and High‐Strength Poly(vinylidene fluoride)/Potassium Sodium Niobate Composite Foams With High β‐Phase Content and Favorable Thermal Insulation via Supercritical CO ₂ Foaming

With the rapid advancement of technology, polymer foams have gained prominence for their lightweight properties, high strength, ease of processing, chemical stability, and thermal insulation capabilities, becoming highly coveted materials in advanced applications. In this study, poly(vinylidene fluoride) (PVDF)/potassium sodium niobate (KNN) composite foams with low density, excellent mechanical properties, and good thermal insulation were successfully fabricated via melt blending and supercritical carbon dioxide (scCO ₂ ) autoclave foaming technology. The results indicate that KNN not only acted as efficient heterogeneous nucleating agents during foaming, increasing cell density, but also promoted α to β‐phase transformation in PVDF. Analyses utilizing Fourier transform infrared spectroscopy and X‐ray diffraction demonstrated a notable rise in the content of β‐phase after foaming, which further increased with higher KNN loading. The foam exhibited significant compressive mechanical characteristics with a KNN concentration of 5 wt%, reflected in a 216.7% rise in compressive specific modulus and a 239.5% enhancement in specific strength. Furthermore, FPK5 achieved a favorable thermal conductivity of 0.031 W m ⁻¹ K ⁻¹ , demonstrating good thermal insulating capability. The work offers a straightforward, effective, and environmentally friendly method for creating PVDF‐based foams appropriate for use in flexible electronics and thermal management.