Investigation of the Use of a Plasticizer-Polymer Sensor Coating with Improved Long-Term Stability in the Liquid Phase
Date of Award
Master of Science (MS)
Electrical and Computer Engineering
Benzene is one of the volatile organic compounds present in crude oil and gasoline. Leakage from underground storage tanks or hazardous waste sites can introduce benzene contamination into nearby groundwater. Benzene is a known carcinogen and its exposure is limited by the Environmental Protection Agency to 5 parts per billion (ppb) in drinking water. Early, accurate detection of the presence of benzene contamination in groundwater supplies is extremely important. Shear horizontal surface acoustic wave (SH-SAW) devices with a chemically sensitive coating can be used for the detection of volatile organic compounds in liquid, such as BTEX (benzene, toluene, ethylbenzene and xylenes). Not all polymers that are chemically suitable to absorb benzene are able to do so in a reasonable time frame due to their glassy nature. The polymer is too rigid which does not allow for rapid benzene absorption. A plasticizer can be added to the selected polymer to lower the glass transition temperature. This makes the polymer more rubbery allowing for rapid analyte absorption. However, most plasticizers will tend to leach out of the polymer over time. The leaching of the plasticizer into the surrounding environment results in an unstable coating. Without a stable coating, reliable, repeatable measurements are not possible. It is the intent of this work to use the plasticizer DINCH in the polymer polystyrene to create a stable coating for the detection of BTEX compounds, with the focus on benzene. Various plasticizer concentrations are investigated as well as coating thickness. Sensitivity to benzene and long-term stability of the coating are tested.