F-POSS nanofillers modified PVDF foam with excellent mechanical and thermal insulation properties

Abstract

Polyvinylidene fluoride (PVDF) foam, known for its low density, high strength, and inherent flame retardancy, has demonstrated significant advantages in various applications. Fluorinated polyhedral oligomeric silsesquioxane (F-POSS), recognized as an ideal nanofiller, contributes to the manufacture of lightweight, high-performance PVDF insulating foam. PVDF/F-POSS composite foams were successfully prepared in this work, employing melt blending and supercritical CO₂ (scCO₂) autoclave foaming techniques that exhibited excellent mechanical performance and thermal insulation capabilities. Crystallization behavior research findings indicated that F-POSS increased the crystallinity of PVDF, functioning as a crystallization nucleating agent. Concurrently, the use of scCO₂ foaming technology promoted phase transitions, increasing the content of β-phase. Scanning electron microscopy (SEM) observations revealed that F-POSS could also serve as a cell nucleating agent, which increased cell density and formed a more uniform cell structure. At 1 wt% of F-POSS, the foams demonstrated excellent compressive mechanical properties, which compressive specific modulus and compressive specific strength increased by 76.9 % and 197.5 %, respectively. In addition, the composite foams exhibited an outstanding low thermal conductivity value of 0.0305 W m⁻¹ K⁻¹. This study provides a simple, efficient and green way for preparing thermal insulation foams consisting of fluorinated polymers and fluorinated nanofillers.