Melting and crystallization temperatures, foaming, and fluid-induced crystallization of poly (ε-caprolactone) in compressed CO2 and N2

Abstract

Melting and crystallization temperatures of poly(ε-caprolactone)(PCL) exposed to CO2 and N2 have been evaluated at pressures up to 125 bar using High Pressure Torsional Braid Analysis. It is shown that in contrast to CO2, exposure to high pressure N2 does not lead to a significant depression of Tm or Tc. Instead, these transition temperatures tend to increase in nitrogen, reflecting more of a hydrostatic pressure rather than a solvent effect. Another factor that may play a role is the fluid-induced crystallization which tends to increase the melting temperature. By conducting foaming at properly selected temperatures along the rigidity reduction paths which are scaled with respect to the melting temperatures in CO2 or N2, foams with low bulk foam densities of about 0.2 g/cm3 could be generated in CO2 at 100 bar and in N2 at 200 bar.