Embedded Eggshells as a Bio-Filler in Natural Rubber for Thermal Insulation Composite Foams

Abstract

Thermal insulation composite foams were prepared from the natural rubber as a matrix phase and an eggshell powder as a calcium carbonate dispersed phase, using chlorinated polyethylene acting as a flame retardant and curing agent at the vulcanization temperature 150°C in a two-roll mill. The main composition of eggshell is calcium carbonate which is more than 96.35 wt%. The obtained composite rubber foams with 50 phr eggshell added possessed the thermal conductivity, compression set, crosslink density, bulk density, and relative foam density values equal to 0.070 W/m.K, 45.0%, 6.95 × 10⁻⁵mol/cm³, 0.58, and 0.63, respectively. The obtained composite rubber foams were of good thermal resistance, good compression set, short curing time, good crosslink density, and light weight, suitable for various applications such as automobiles, storage tank, and transport packaging. Furthermore, the scanning electron micrographs, X-ray diffraction patterns, specific heat, and physical properties (bulk density, crosslink density, and relative foam density) were taken or measured to investigate the microstructures, phase compositions, thermal properties, and characteristics of the insulating composite foams and were reported here.