Semi-Rigid Composite Foams of Calcium Sodium Aluminosilicate from Eggshells Embedded in Polyurethane

Abstract Calcium sodium aluminosilicate (CaNaAlSi2O7) ceramic powder was prepared from eggshells as a raw material via the sol-gel process at room temperature. The CaNaAlSi2O7 ceramic particles were embedded as a dispersed phase in the polyurethane (PU) foam matrix via a direct foaming process. The calcium sodium aluminosilicate (CaNaAlSi2O7) ceramic powder had a high specific surface area of 38.89 m2 g−1, and a fine average particle size of 13.27 μm, whereas the PU foam had a low specific surface area of 1.00 m2 g−1, and of light weight. After adding 10 vol% CaNaAlSi2O7 to the PU, the composite foams possessed a high specific surface area of 6.0 m2 g−1, a bulk density of 0.213 ± 0.012 g cm−3, a high decomposition temperature of 790 °C, and a high compressive Young's modulus of 346.0 ± 76.5 kPa. The CaNaAlSi2O7/PU composite foams provided good thermal conductivity, uniform pore size and particle size distribution, good bridge bonding, and with microcellular interconnecting cells. The CaNaAlSi2O7/ PU semi-...