Effects of Environmental and Test Conditions on VOC Emissions from “Wet” Coating Materials

Abstract

In this paper, numerical simulations have been conducted to study the effects of key environmental and test conditions (air velocity, temperature, film thickness, and sample application time) on volatile organic compound (VOC) emissions from a "wet" coating material (wood stain). Simulation results indicate that air velocity and sample application time only significantly affect the emission profiles in the early stage. Film thickness, on the other hand, affects long-term emissions. Temperature can affect both the short-term and long-term emissions.

Predicting emission characteristics of volatile organic compounds from wet surface coatings

“…Based on these arguments, it can concluded that the concentration dependence of VOC diffusivity in polymeric surface coating materials should be taken into account when there is a big change in the concentration of VOC during total emission period, which is the case for wet coatings and when the glass transition temperature of the coating material is around room temperature and higher. In the literature Yang et al [13,15,22] and Haghighat and Huang [19] used second-and third-order empirical equations to describe concentration dependence of VOC diffusivities. Different from these approaches, the diffusion model used in this study has a physical background and can be applied to any VOC-coating system if its parameters are available.…”

“…In a few diffusion models, external convective mass transfer resistance was neglected and only internal diffusion within the material was taken into account [11,12]. More complete models were developed by taking into account combined effects of internal and external mass transfer resistances [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. In these models, the material is treated as a homogenous medium that can be characterized by an effective diffusion coefficient.…”

“…The initial concentration of VOC was assumed to be either constant [13][14][15][16][17][18][19][20][21][22]24,25,28] or nonuniform [23,26,27]. To predict the concentration of VOCs in air, macroscopic mass balances were generally used [16][17][18][19][20][21][23][24][25][26][27][28], on the other hand, in a few studies, two-or three-dimensional momentum and mass transfer equations were solved [13][14][15]22]. Most of these models assume that equilibrium relationship is linear and the diffusivity of VOC in the coating material is constant.…”

“…In the case of wet coating materials, the initial concentration of VOC in the material is high, thus, the dependence of VOC diffusion coefficient on VOC concentration cannot be ignored and equilibrium relationship deviates from linearity. In a model developed by Yang et al [13,15,22] for simulating VOC emissions from wet coating materials, the diffusion was considered a thermally activated process and the temperature dependence of the diffusivity was described by Arhenius equation. To describe the concentration dependency, a third power empirical equation was used.…”

“…This diffusion model does not predict infinitely small diffusivities, however, the empirical factors in the model confine its relevancy. Both in the models of Yang et al [13,15,22] and Haghighat and Huang [19], Henry's law was used as an equilibrium relationship although this thermodynamic expression is valid at low concentrations.…”