Emission modeling of styrene from vinyl ester resins

The use of vinyl ester (VE) resins in the composites industry has increased in the last decade, and the trend is projected to continue. Styrene is a commonly used co-monomer in VE resins, which acts as a reactive diluent and is required in many liquid molding methods to reduce viscosity and increase gel time. The emission rate of styrene from VE resins is affected by various parameters, including styrene content, temperature, and resin surface-to-volume ratio. This study experimentally measured the effect of these parameters on styrene emission rates from VE resins. It was observed that the emission rate and amount of styrene decreased with decreasing surface-to-volume ratio, temperature, and styrene content. It is also shown that diffusion coefficient and evaporation coefficient of styrene have an exponential relationship with temperature, while they remained constant with initial styrene concentration and aspect ratio. Emission rate and amount decreased with increasing resin initial depth to radius ratio. The emission profiles were self-similar for different aspect ratios and were scaled by the ratio of the instantaneous sample depth to radius. Overall, the effect of these various parameters on the emission profile can be accurately modeled using a modification of a simple one-dimensional diffusion model based on the Crank solution to diffusion through a planar sheet.