Some thermodynamic and kinetic properties of the system PETG-CO2, and morphological characteristics of the CO2-blown PETG foams

The solubility of CO2 in PETG, a glycol-modified PET, was measured at diffe rent temperatures and over a broad pressure range, and diffusion coefficien ts were derived at the corresponding conditions. The solubility of CO2 is q uite high. For example, almost 15 wt% CO2 can be dissolved in PETG at 35 de grees C and 6.0 MPa. Consequently, CO2 is a good blowing agent for PETG. Ce llular foams in the density range of about 0.04 to 1.2 g/cm(3) and cell dia meters in the range of about 10 to 150 mu m were produced. The foam density and the cell size were found to depend on the foaming temperature and time , with larger cells obtained at higher temperatures or when the sample was foamed for a longer time. The foam density decreased with an increase in th e foaming temperature to about 90 degrees C, beyond which the density tende d to increase slightly due to the cell collapse or coalescence. The density reduction also depended on the pressure at which the polymer was saturated with CO2; the higher the saturating pressure at a given temperature, the g reater the density reduction.