(382d) Application of Plasticized Pema/PMMA Sensing Film for Sorption of BTEX Compounds in Vapor Phase Using a Quartz Crystal Microbalance (QCM) at 298.15 K

Detection of volatile organic compounds (VOC’s) in the environment is important for human-health and wellness. Long term exposure to certain VOC’s like benzene, toluene, ethyl-benzene and xylene (BTEX) have severe carcinogenic effects on human health. Acoustic wave devices such as the surface acoustic wave (SAW) device can be used for sensing BTEX compounds in both vapor and liquid phases. The quartz crystal microbalance (QCM) is a low frequency acoustic wave device, which can be used to characterize polymer film sensing quickly and easily by studying the sorption properties of BTEX compounds in them. In this work, thin films (~ 0.5 microns) of polymer/plasticizer blends are spin-coated on a 5MHz QCM for the detection of VOC’s. Polymer/plasticizer combinations of poly-ethyl methacrylate (PEMA), poly-methyl methacrylate (PMMA) and a copolymer of PEMA/PMMA with di-n-butyl phthalate (DBP), di-n-butyl sebacate (DBS) and n-butyl stearate (BS) are used for the detection of BTEX in vapor phase. The working apparatus consists of a stream of solvent vapor diluted with nitrogen to an arbitrary concentration passing over the QCM oscillated to its resonant frequency. The sorption data are reported at 298.15 K as activity vs. weight fraction curves and are interpreted with the Flory-Huggins ternary model. The addition of plasticizer modifies the free volume properties of the polymer, thereby increasing diffusion and sensitivity of BTEX vapors. The plasticizer composition is tailored to 17.5%, for maximum sorption with minimal viscoelastic effects. The sorption and sensitivity of BTEX is interpreted and studied in terms of plasticizer type and concentration.