Sorption and diffusion of volatile organic compounds in polydimethylsiloxane membranes

Abstract

Sorption and diffusion of ethanol, 1,1,1-trichloroethane (TCA), and trichloroethylene (TCE) were investigated in polydimethylsiloxane (PDMS) membranes using a gravimetric technique. The thermodynamic equilibrium and kinetic properties were evaluated at temperatures of 25, 100, and 150ЊC. The sorption isotherms for TCA and TCE can be correlated well using the Flory-Huggins model. However, a three parameter Koningsveld-Kleinjtens variation to the Flory-Huggins equation is required for correlation of the ethanol isotherm. The solubility coefficients of TCA and TCE increase with activity, but it remains almost constant for ethanol. The calculated sorption energies reveal high positive heat of mixing for ethanol. TCA and TCE sorption in PDMS decreases strongly with temperature as opposed to ethanol. Clustering function analysis is used to explain the anomalous ethanol sorption and diffusion behavior in PDMS. TCA and TCE diffusivities do not exhibit large variations with volatile organic compound activity. However, ethanol demonstrates a maxima in its diffusivity at activities where it has minimum clustering tendencies.

Sorption studies of volatile organic compounds in a divinyl‐terminated poly(dimethylsiloxane)–oligo polymer

“…A Flory–Huggins (F–H) model has been applied to describe VOC sorption isotherms 10–14. For a binary polymer–VOC system, the F–H model can be written as follows: where χ 12 is the F–H interaction parameter between a VOC (component 1) and a polymer (component 2) and ϕ 1 is the VOC volume fraction in the polymer film.…”

Vapour permeation of VOC emitted from petroleum activities: Application for low concentrations

“…Given that solubility is the limiting step in VOC permeation through rubbery polymers, one can infer that propylene transport depends on its inherent solubility in the PDMS membrane, which is relatively low. The effect of VOC components on permeation of other could be better explained in terms of thermodynamic parameters using Flory-Huggins interaction parameters or engaged species induced clustering (ENSIC) model [49,[51][52][53]. However, such an analysis was beyond the scope of this paper.…”

D-Fiber volatile organic compound sensor

“…Polydimethylsiloxane (PDMS), a polymer commonly used in micro fabrication, exhibits selective transport for organic molecules with respect to polar molecules such as water and low molecular weight gases such as nitrogen, oxygen, and helium [7]. PDMS is more penetrable to large, hydrocarbon-based VOCs than to small molecules [8].…”

“…5 is due to the solubility coefficient of dichloromethane in PDMS. As the concentration in PDMS increases, the solubility increases due to considerable swelling of the polymer and creation of more free volume in the polymer to hold additional VOCs [7]. The exponential increase in solubility for each chemical type is dependent on the difference of solubility parameters between the chemical and PDMS.…”