Carbon Capture Utilization for Biopolymer Foam Manufacture: Thermal, Mechanical and Acoustic Performance of PCL/PHBV CO2 Foams

Biopolymer foams manufactured using CO₂ enables a novel intersection for economic, environmental, and ecological impact but limited CO₂ solubility remains a challenge. PHBV has low solubility in CO₂ while PCL has high CO₂ solubility. In this paper, PCL is used to blend into PBHV. Both unfoamed and foamed blends are examined. Foaming the binary blends at two depressurization stages with subcritical CO₂ as the blowing agent, produced open-cell and closed-cell foams with varying cellular architecture at different PHBV concentrations. Differential Scanning Calorimetry results showed that PHBV had some solubility in PCL and foams developed a PCL rich, PHBV rich and mixed phase. Scanning Electron Microscopy and pcynometry established cell size and density which reflected benefits of PCL presence. Acoustic performance showed limited benefits from foaming but mechanical performance of foams showed a significant impact from PHBV presence in PCL. Thermal performance reflected that foams were affected by the blend thermal conductivity, but the impact was significantly higher in the foams than in the unfoamed blends. The results provide a pathway to multifunctional performance in foams of high performance biopolymers such as PBHV through harnessing the CO₂ miscibility of PCL.

Supercritical CO2 Processed Polystyrene Nanocomposite Foams

Polystyerene (PS) nanocomposite foams were prepared using CO2 supercritical fluid (SCF) as a solvent and blowing agent. PS was first in situ polymerized with 0, 1, and 3% Montmorillonite-Layered Silicate (MLS) mixtures, which were then compression-molded into thin laminates. The laminates were foamed in a batch process at temperatures and pressures within the range of 60–85 C and 7.6–12 MPa. Characterization was accomplished with scanning electron microscopy (SEM), Differential Scanning Calorimetry (DSC), and X-ray Diffraction (XRD). SEM images revealed the effects of different processing parameters on the foam’s cellular morphology, and also showed that the MLS layers were arranged in alignment with the foam cell walls. DSC data indicated that different concentrations of MLS have a notable effect on the glass transition temperature (Tg) of the composite, and that the foaming process itself alters the endothermic behavior of the material. XRD spectra suggested that the PS–MLS composite had an intercalated structure at both the 1 and 3% mixtures, and that the intercalation may be enhanced by the foaming process.