Impacts of digestion protocols on chemical and natural fibers

International audienceMicroplastics are an emerging environmental issue. It has been shown that two principle types of microplastics exist: fibers and fragments. Fibers have been encountered in the air, in rivers and oceans, in sediments, in fish and even in several food products (such as honey, beer and bottled water). Organic matter removal is needed to quantify microplastics in environmental samples. Different digestion protocols are used for extraction of microplastics. However, there is a gap in data regarding the impacts of those protocols on fiber integrity. Indeed those impacts are generally estimated for fragments and not for fibers. This work focuses on the impact of four different digestion protocols on seven different fiber types. The effects of those protocols on fiber integrity have been characterized. The protocols to be tested were selected based on their frequency in the literature : KOH 10 % at 40°C for 24 hours; KOH 10% at 60°C for 24 hours ; NaClO 9% at room temperature for 12 hours ; H2O2 30% at 40°C for 48 hours. We decided to test the KOH protocol with two different temperatures (40°C and 60°C) to assess temperature impact on fibers. Other protocols such as Fenton reagent and enzymatic digestion could also be tested. Each protocol is tested on the 7 most used fibers in the world in textile apparel: three synthetic (polyamide 6.6 (PA 6.6), polyethylene terephthalate (PET) and Acrylic), one artificial (viscose), two vegetal (cotton and flax) and one animal (wool). Those fibers are characterized before and after the digestion and several of their properties are assessed: their weight, their linear mass density, their mechanical properties (tenacity, elongation) and their zeta potential. Their cross-sectional and longitudinal degradations are characterized using optical microscope. For the synthetic fibers, their crystallinity content is evaluated by Differential Scanning Calorimetry (DSC). Finally, all the fibers are characterized using an infrared spectroscope and a scanning electron microscope (SEM). The fibers are currently being analyzed. A comparison between the four digestion protocols will be made in order to conclude which one should be the most appropriate for fiber analysis