Improving thermal insulation properties of lightweight epoxy resin matrix composites with millimeter-sized hollow glass microspheres/epoxy hollow spheres

• Millimetric hollow glass microspheres/epoxy(HGMs/EP) hollow spheres were prepared. • HGMs/EP hollow spheres showed low density and excellent mechanical properties. • A lightweight, thermal insulated EP composite with lattice structure was designed. • EP composites showed good thermal insulation properties. • Thermal insulation mechanism of the EP composites was proposed. In this study, a novel, lightweight, thermally insulated epoxy resin (EP) composite was designed and fabricated by arranging hollow glass microspheres/epoxy resin (HGMs/EP) hollow spheres and EP matrices using a combination of templates and a simple casting method. The designed HGMs/EP exhibited low density and excellent thermal insulation properties, and their size was of the order of millimeters. HGMs/EP hollow sphere–reinforced EP composites exhibit considerably lower density (0.73 ± 0.06 g/cm 3 ; 39.16% lower) and thermal conductivity (0.121 ± 0.016 W/(m·K); 37.31% lower) than the traditional HGMs/EP composites with the same HGM content. Overall, the designed HGMs/EP hollow sphere–reinforced EP composites are excellent candidates for providing thermal insulation in construction materials.