Application of Carbon Dioxide Capture Technology in the Process of Polyethylene Foaming Materials

Blowing agents are key compounds for the preparation of polymer foams. However, the use of chemical blowing agents is being curtailed to address the adverse impacts on public health and the environment issues. Moreover, physical blowing agent supercritical carbon dioxide (CO₂) requires harsh experimental conditions such as high temperature and pressure, resulting in high energy consumption and safety problems. In this study, CO₂ was captured through amines under atmospheric pressure to form ammonium carbamate salts, which reversibly released under heating as blowing agent. Integrated nucleating-blowing agents were fabricated by heterogeneous nucleating agent (cyclodextrin nanosponges, NS) loaded with ammonium carbamate salts. The effects of types and contents of amines on the thermal and CO₂ capture efficiency were investigated. Results revealed that only amines with strong basicity like 1,2-cyclohexanediamine (TRK) was the CO₂ capture candidate to prepare ammonium carbamate salts. The mass ratio was 1:4 for NS and TRK (NS: TRK-CO₂(1:4)), and the release temperature of CO₂ was 137 ℃. Foamed polyethylene (PE) composites were prepared by molding process with NS: TRK-CO₂(1:4). Scanning electron microscopy (SEM) images were used to study the morphology of the nanocomposites. The optimum cell morphology was obtained with 5 wt% NS: TRK-CO₂(1:4), the cell diameter was 116 μm, and the cell density was 7.9 × 10⁴ cell/cm³. The best fabricated microcellular PE/NS: TRK-CO₂(1:4) composite presented excellent mechanical, thermal and sound insulating performance. The maximum tensile strength of the PE composite was 25.48 MPa, and the maximum bending strength was 11.27 MPa. The impact strength was 5.77 KJ•m^-2, more than 1.5 times higher than pure PE. The thermal conductivity was as low as 0.076 W/m•k, the sound absorption coefficient was 0.737 at 1500 Hz, and the noise reduction coefficient was 0.459.