Polymer Sorption of VOCs for Indoor Air Quality and Atmospheric Sampling

Melissa Morris, ANYL 3rd year,
Jimenez group

"Polymers comprise a substantial fraction of the surfaces in indoor environments, where we spend about 90% of our time. It is well-known that polymers absorb gas-phase volatile organic compounds (VOCs), which directly affect indoor and outdoor air quality, but few studies have investigated the interactions between polymers relevant to indoor materials and VOCs. To better understand the role of carpets on indoor air quality, we have extended recent studies from our groups on polymer-VOC interactions to include polymers relevant to carpets (nylon, polyester, polypropylene, polyethylene), as well as carpet itself. We use a Vocus proton transfer mass spectrometer to measure sorption of a series of 2-ketones by polymer or rolled-carpet tubes. Then, we use two sorption models adapted from Pagonis et. al. (2017) and Algrim et. al. (2020) to quantify sorptive capacities (and for highly-sorptive polymers, VOC diffusion coefficients) for these materials. The polymers were found to increase in sorptive capacity as: nylon, polyester, polypropylene and polyethylene. Polypropylene and polyethylene (often used in carpet backing) are more sorptive for the same geometry. However, nylon and polyester (the materials of carpet fibers), do comparable sorption when scaled up to account for the enormous surface area of carpet fibers. The sorptive capacities of carpet polymers suggest that carpet indoors is comparable in sorptive capacity to paint (Algrim et al. 2020) and wood (Ziola et al. 2022). Sorption experiments also showed that nylon carpet irreversibly sorbs C4-C9 acids. While testing carpet-relevant polymers for VOC sorption, we tested a few additional polymers relevant to atmospheric sampling, including TSI conductive silicone tubing. We found that conductive silicone tubing only transmits very high-volatility compounds (C* > 1e7 ug m-3, such as terpenes and more volatile species). We have demonstrated the use of a system with tubing of multiple polymer materials as a separator of gas-phase compounds into volatility classes. This technique could be useful e.g. for measuring chemical characteristics (i.e. OH reactivity or SOA potential) of complex mixtures of gas-phase compounds (such as ambient air) according to volatility class."