Preparation of pros-foam sheets and their epoxy foams using the solid-state carbamate-foaming technique

The foaming of epoxy resin is a challenge process in optimizing the flow foaming and curing to obtain a homogeneous cellular structure. This study presents a new method for preparing of epoxy foams, which is called solid-state carbamate foaming technique. The epoxy resin was formulated based on epoxy, hardener (amine or polyamide) and carbamate. The first step is to precure an epoxy resin and hardener to form a solid-state pros-foam sheet. The second steps are foaming and complete curing. Carbamate decomposes to form CO2 for foaming and revived amine for final curing. By changing the amine or polyamide hardener, and their ratio with carbamate, epoxy foam with density of 110–150 kg/m3 after free expansion was achieved. Epoxy foams with 3 mm (density of 407–434 kg/m3) and 4 mm thickness (density of 332–352 kg/m3) were expanded in a mold. The final foams have a glass transition temperature of 119–157 °C and storage modulus at 30 °C of 90–210 MPa.