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Effect of Pressure on the Melting Point of Pluronics in Pressurized Carbon Dioxide

Ruchir Bhomia, Vivek Trivedi, John C. Mitchell, Nichola J. Coleman, Martin J. Snowden
2014 Industrial & Engineering Chemistry Research  
The melting points of Pluronic® F-77, F-127, F-68, F-38 and F-108 were investigated in pressurised CO 2 between a pressure range of (2.0 to 50.0) MPa. Unprocessed and CO 2processed Pluronic® samples were analysed by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). A melting point depression in the range of (18.1± 0.5 to 19.3± 0.3) K was observed for all Pluronics® studied in this work. The melting point of Pluronics® in pressurised CO 2 was found to be independent of
more » ... o be independent of their molecular weight and poly (propylene oxide) [PPO] content. Analysis by DSC and PXRD revealed that CO 2 processing had no impact on the morphology of Pluronics®. Introduction- Any substance above its critical temperature and pressure can be defined as a supercritical fluid 1 . A supercritical fluid has liquid-like density and gas-like diffusivity which can also be tuned by varying operational temperature and pressure 2 . SCCO 2 is by far the most commonly used supercritical fluid because of its low critical temperature (304.3 K) and critical pressure (7.33 MPa). Moreover, it is readily available, nontoxic, non-flammable, non-corrosive, inexpensive, environmentally benign and easy to remove from reaction systems. SCCO 2 has found its use in the chemical industry as an alternative to organic solvents and it is also considered to be desirable for the processing of thermolabile materials 3,4 . Supercritical fluid technology has applications in a variety of fields such as, extraction, cleaning, synthesis etc. 5 . One such application includes polymer processing. The interaction of CO 2 with polymers is an interesting phenomenon and plays a significant role in various polymer processing operations 6-8 . The depression in melting point (T m ) or glass transition (T g ) temperature in polymers due to the sorption of CO 2 is a well-known phenomenon which is dependent on various factors such as crystallinity and presence of CO 2 -philic moieties 9-14 . Amorphous polymers are reported to show higher interactions with CO 2 than crystalline polymers 15,16 . These interactions can be
doi:10.1021/ie501344m fatcat:gl2vxqevrfekdhbhcjmgmeyewi