Viscosity studies of poly(DL‐lactic acid) in supercritical CO2 |
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| Authors: | Catherine A Kelly Steven M Howdle Kevin M Shakesheff Mike J Jenkins Gary A Leeke |
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| Institution: | 1. School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom;2. School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom;3. School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom;4. School of Metallurgy and Materials, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom |
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| Abstract: | The effect of supercritical CO2 on the viscosity and activation energy to viscous flow of PDLLA is investigated, using a high pressure parallel plate rheometer, over a range of temperatures (50–140 °C) and pressures (5–12 MPa). The Cross model is fitted to the data to enable calculation of the zero shear viscosity and critical shear rate. A significant decrease in the viscosity is observed on increasing both variables; however, at high temperatures, the pressure effect becomes negligible. An increase in the critical shear rate is also observed on raising the pressure, indicative of a reduction in the relaxation time of the polymer. Manipulation of the Arrhenius equation shows a reduction in the activation energy to viscous flow as the pressure is increased. Together, these results show that the melt processing temperature of PDLLA can be reduced in the presence of supercritical and high pressure CO2. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 |
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| Keywords: | activation energy polylactide processing supercritical CO2 viscosity |
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