Pressure sensitive adhesives for quantifying microplastic isolation

Abstract

Microplastics are a growing environmental concern, with a large body of evidence documenting distribution of plastic material in virtually all environmental compartments. Countermeasures that help to bind, aggregate, or coalesce these collections might result in lower human and animal exposures. Pressure sensitive adhesives (PSAs) have been identified as a viable microplastic (MP) capture mechanism with a range of potential use conditions. As with any countermeasure, there is a need to evaluate potential solutions in terms of collection efficiency, cost, ease of installation, robustness etc. Expanding on our previous work, spray-coated PSAs were investigated as submerged surfaces for use in a quick and low-cost quantitative method to assess MP binding in aqueous mediums. Resins containing two differing molecular weights of poly(2-ethylhexyl acrylate) PSA (92 k and 950 k), and a 50:50 by weight mixture of the two resins were applied as spray-coated substrates to compare the effect of resin composition on MP-adhesive binding. Thin films of PSA (92 k 6 ± 1 μm, 950 k 4 ± 2 μm, 50:50 BD 6.5 ± 1 μm) were sprayed on borosilicate glass slides using a commercial air brush. Polydisperse nylon-12 particles varying in size from 15 to 30 µm in diameter were dispersed in water at concentrations between 0.01 and 5 mg mL−1 and agitated under ambient conditions to assess adhesive binding as quantitative comparisons of microparticle capture. Mixed assays were also performed comparing binding of common MP species including polyethylene (50, 200 µm), polystyrene (10 µm), and polyester fibers (1000 µm) to understand how varying composition, size, and form factor affect adsorption. The glass slide method showed increasing linear trends of particle binding with increased adhesive exposure time and MP concentration. The adhesive wettability to particles demonstrates bounding parameters under which softer adhesives excel at MP capture but may compromise adhesive film integrity. Low cost, ease of sample preparation, and small footprint of the adhesive testing method suggest promise for research use in under-resourced regions and field work.