Graduation Year

2005

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Chemical Engineering

Major Professor

Venkat R. Bhethanabotla, Ph.D.

Committee Member

Babu Joseph, Ph.D.

Committee Member

Scott W. Campbell, Ph.D.

Keywords

QCM, VLE, Benzene, N-hexane, Dichloroethane, Chloroform

Abstract

Thickness shear mode (TSM) sensors, also known as quartz crystal microbalances (QCM) are a class of acoustic wave sensors that have been used for gas phase sensing. In this thesis this device is used to measure vapor-liquid equilibrium data for copolymers of poly(styrene-butadiene) at 294K.

Copolymers of poly(styrene-butadiene) with varying percentages of styrene (85%, 45% and 21 %) were studied with benzene, n-hexane, dichloroethane and chloroform as solvents. Literature data for pure polystyrene/benzene and polystyrene/chloroform and polybutadiene/benzene were obtained to complement the measured data.

Obtained experimental data were fit with a modified Flory-Huggins model and compared with the predictions of three models (UNIFAC-FV, Entropic-FV, and GK-FV). Flory-Huggins model gave a good quantitative fit for the solvent activities in the copolymer solutions. All models UNIFAC-FV, GK-FV and Entropic-FV gave good predictions for poly(85% styrene-15% butadiene) copolymer/solvent and poly(45% styrene-55% butadiene) copolymer/solvent systems. All models could not predict well for poly(21% styrene-79% butadiene)/ chloroform system, yet the same models gave good predictions for the same copolymer with benzene, n-hexane and dichloroethane systems. All models predicted very well for 21% styrene in copolymer and n-hexane system and did not do well with chloroform as solvent. GK-FV and entropic-FV predicted better for 21% styrene in copolymer and solvents except chloroform.

A fully instrumented and automated test-bed consisting of a temperature controlled vapor dilution system, a precision impedance analyzer, and computer for data acquisition in Labview was developed in-house to evaluate the performance of the coated TSM devices in sensor applications as well as in sorption data measurement.

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