A Thermodynamic Investigation of the PVT, Solubility and Surface Tension of Polylactic Acid (PLA)/CO₂ Mixtures

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Abstract

This thesis illustrates a comprehensive study on the PVT, solubility and surface tension properties of polylactic acid (PLA) with dissolved CO₂ based on thermodynamic models. The solubility of CO₂ in PLA melt was calculated by means of a gravimetric method, using a Magnetic Suspension Balance (MSB). The swelling volume of the polymer/gas mixture due to dissolution of gas was compensated for by direct measurement through a view cell or by theoretical models such as Simha Somcynsky (SS) - Equation of State (EOS) and Sanchez Lacombe (SL) - Equation of State (EOS). Three grades of PLA (i.e., PLA3001D, PLA8051D, and PLA4060D) were chosen. It was observed that the pressure, temperature, D-content and Molecular weight variance had an effect on the swelling and solubility.

The surface Tension of PLA/CO₂ mixture was also calculated from the captured image using the Axsymmetric Drop Shape Analysis (ADSA). The effects of varying the pressure, temperature, and molecular weight on surface tension were investigated.

Cited Works (6)

Year	Entry
1995	Park CB, Baldwin DF, Suh NP. Effect of the pressure drop rate on cell nucleation in continuous processing of microcellular polymers. Polym Eng Sci. March 1995;35(5):432-440.
1996	Park CB, Suh NP. Filamentary extrusion of microcellular polymers using a rapid decompressive element. Polym Eng Sci. January 1996;36(1):34-48.
1999	Sato Y, Fujiwara K, Takikawa T; Sumarno, Takishima S, Masuoka H. Solubilities and diffusion coefficients of carbon dioxide and nitrogen in polypropylene, high-density polyethylene, and polystyrene under high pressures and temperatures. Fluid Phase Equilib. August 1999;162(1-2):261-276.
1993	Park CB. The Role of Polymer/gas Solutions in Continuous Processing of Microcellular Polymers [PhD thesis]. Cambridge, MA: Massachusetts Institute of Technology; May 1993.
2008	Li YGG. Development of a Novel Visualization and Measurement Apparatus for the PVT Behaviours of Polymer/gas Solutions [PhD thesis]. University of Toronto; 2008.
2008	Li G, Leung SN, Hasan MM, Wang J, Park CB, Simha R. A thermodynamic model for ternary mixture systems: gas blends in a polymer melt. Fluid Phase Equilib. April 25, 2008;266(1-2):129-142.