A method for fabricating polyvinylidene fluoride/poly methyl methacrylate/graphite nanoplates nanocomposites foams with high strength, large expansion ratio and outstanding heat insulation properties

Developing lightweight and high-performance polymer foams for heat insulation is of utmost significance for energy conservation, emission reduction, and improving energy efficiency. Introducing carbon fillers such as graphite nanoplates (GNPs) can effectively reduce heat radiation in foams and greatly enhance their mechanical and flame-retardant properties. However, there are technical challenges in achieving eco-friendly and scalable production of lightweight polymer/GNP nanocomposite foams, including poor dispersion of GNPs and lower foaming ratios. In this work, a method for fabricating lightweight nanocomposite foams through melt blending combined with a carbon dioxide molten-foaming process was proposed. By using this method, the ultralight, high-strength, and hydrophobic polyvinylidene fluoride (PVDF)/poly (methyl methacrylate) (PMMA)/GNP nanocomposite foams with excellent heat insulation and flame-retardant properties were successfully prepared. It was found that the addition of GNP improves the melt viscoelasticity and increases the initial crystallization temperature of PVDF. Furthermore, GNPs can also expand the foaming temperature window, refine the cell size, and induce open-cell structures in the foams. The nanocomposite foams fabricated using this method have a foaming temperature window of over 20 °C, a foaming ratio exceeding 40, and a density below 0.04 g/cm3. Thanks to the higher foaming ratio, well-developed open-cell structures, and the heat radiation attenuation effect of GNPs, the nanocomposite foam exhibits a remarkably low thermal conductivity of 30.14 mW⋅m−1⋅K−1. Additionally, the foams display favorable compressive mechanical properties, hydrophobicity, and flame retardancy.