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FLUORESCENCE SPECTROSCOPIC ANALYSIS OF BIODEGRADED PRESSURE-SENSITIVE LABELS MADE FROM AGRO- INDUSTRIAL AND POST-CONSUMER WASTE

Today, more than ever, sustainability is at its highest peak of daily interest for all business sectors, especially involving label and packaging industries. Usage of paper products made from alternative fiber sources is a very important topic that directly supports circular economy in everyday life. Although paper products should be recycled or re- used as secondary source of raw - material, a vast volume of products end their life at landfill, especially still in our region, causing excessive accumulation in the environment. For the purpose of this research, fluorescence intensity was measured on three different biodegraded pressure sensitive label material samples (PSL), made from agro-industrial and postconsumer waste. PSL materials utilized in this research are widely used for labelling various products, for example, wine, luxury products, food etc. and are compiled of 3 parts: facestock, adhesive and liner. PSL materials are enriched with optical brighteners to give the final product the desired optical properties. Fluorescence spectroscopy is a direct measure of optical brightener concentration within the substrate. Biodegradation was performed by usage of soil burial test under aerobic conditions. Laboratory soil burial experiments were conducted at room temperature (25±2°C) by placing the unprinted label paper substrates ; facestock and adhesive (delaminated from the liner) horizontally in field soils in 2L laboratory glass containers, orientated adhesive down. The water content of the soil was adjusted to 40 % of its maximum water retention capacity. Substrates were buried for a period of 2, 4, 7, 10 and 13 days. Sample’s fluorescence intensity was measured before and after incubation in the soil containers. The samples were dug out after designated time, rinsed with distilled water to remove soil particles from the surface, air dried and measured. Fluorescence intensity was measured by using Ocean Optics USB2000+ spectrometer using a 30 mm wide integrating sphere under (8:di) measuring geometry with the addition of LSM Series LED light source at 365 nm. LED light source is operated via a smart controller during the measurement. A constant current of 0.140 A was kept stable in order to maintain a constant excitation light source with the aim to excite fluorescence whitening agents within the samples. As previously research shows the presence of optical brighteners in composition of fibre based PSL, fluorescence spectroscopy of biodegraded samples indicates decomposition of optical brighteners.

pressure sensitive labels ; fluorescence spectroscopy, sustainable self-adhesive labelling materials, biodegradation

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