Expanded polystyrene boards are produced by mixing resin with polymers, injecting a catalyst during the heating process, and then extruding them into continuous closed-cell foamed rigid plastic sheets. These sheets feature an independent, sealed bubble structure inside, making them an environmentally friendly thermal insulation material with excellent properties such as high compressive strength, low water absorption, moisture resistance, impermeability, light weight, corrosion resistance, and ultra-anti-aging (virtually no aging after long-term use) with a low thermal conductivity coefficient.