Date of Award

2008

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Chemical Engineering

First Advisor

A Lohi

Second Advisor

S Upreti

Third Advisor

J Wu

Abstract

Solubility and its measurement of different materials including polymers, drugs, proteins, peptides and many other organic or non organic compounds in supercritical fluids are of great importance in a wide variety of applications. These applications include: production of controlled drug delivery systems, powder processing, pollution prevention, spraying paints and coatings, and food processing.

Supercritical fluids are getting more interest since the last two decades due to their abilities in replacing VOC solvents, and because of their tunable properties that could be achieved by varying their pressure and temperature in getting powerful solvents. Supercritical fluid is a substance under pressure above its critical temperture. Under supercritical conditions the distinction between gases and liquids does not apply and substnace can only be described as a fluid. Superciritical fluides have properties intermediate between those of gases and liquids, controlled by the pressure. They do not condense or evaporate to form a liquid or a gas. Fluids such as supercritical carbon dioxide offer a range of unusual chemicla possibilites in both synthetic and analytical chemistry. Supercritical fluids have solvent poer similar to a light hydrocarbon for most solutes.

Carbon Dioxide as supercritical fluid is the msot common and useful sovlent in dissolving different kinds of materials because of its unique features like non toxicity, inflammability, its low critical pressure and critical temperature values, and its low cost. By adjusting the pressure and temperature of Carbon Dioxide above its Pc and Tc, we can modify its powerful to dissolve materials such as Polymers, Drugs, Proteins, and other organic and non organic materials.

Polyethylene Glycol polymers have a low toxicity and they are used in a wide variety of products. As a biodegradable polymer, PEG can be used alone or with other biogdegradable polymers as a drug career into humans and/or animals bodies after getting dissolve with the compatible drugs or proteins in supercritical carbon dioxide.

The solubility of Peg of different molecular weights (PEG 600, PEG 1500 , PEG 6000, and PEG 12000) in Supercritical Carbon Dioxide is measured at different pressures (from 15 to 50 Mpa) and at temperatures (from 313 to 366 K). Also the saturation time that needed to reach the equilibrium state between the polymer and the supercritical fluid at the desired conditions is estimated. In general, the solubility of PEG in SC C0₂ increased with pressure and decreased with temperature due to the density effect of SC CO₂ which is increasing with pressure and decreasing with temperature. Almost PEG of different molecular weights is follow the same solubility pattern.

Static method is used to measure the PEG solubility and the measurement is analyzed by using a microgram scale and this method is compared with other methods.

Low molecular weight PEG polymers have higher solubility than that of high molecular weight polymers at the same supercritical conditions of P, V, and T. Mixing process was found to have a strong effect in reaching the two phase equilibrium state and in getting polymer dissovled properly. Best fitting empirical equation is used to figure out the solubility pattern and its relationship to pressure and temperature.


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