Rheological studies of polycaprolactone in supercritical CO2

A high pressure parallel plate rheometer is utilised to probe the rheological properties of polycaprolactone (PCL) over a range of temperatures (80–120 °C) and CO2 pressures (atmospheric to 100 bar). Interpretation of storage/loss modulus against angular frequency plots show that the reptation time of PCL can be significantly reduced by the addition of 60 bar CO2. This reduction is equivalent to heating the polymer by 20 °C. Application of a time/temperature superposition, coupled with the Arrhenius equation, shows that the addition of CO2 also lowers the activation energy to flow from 31.3 to approximately 21 kJ mol−1.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Reduction in the reptation time of PCL on the addition of supercritical CO2. ► Reduction equivalent to heating the polymer by 20 °C. ► Activation to flow of PCL calculated as 31.3 kJ mol−1. ► Reduction in the activation energy to flow of 10 kJ mol−1 on the addition of scCO2.