Assessment of the impact of cellulose, adhesive labels and metals on the chemical recyclability of high-impact polystyrene from yogurt cups

Trace amounts of auxiliary food packaging components, such as paper adhesives and inks, limit the ability to selectively produce value-added products through chemical recycling. This study evaluates the effect of paper labels, adhesive residues and metal pollutants from labels and additives used in the manufacture of yogurt cups on the degradation products resulting from the chemical recycling of post-consumer HIPS food packaging via non-catalytic pyrolysis. Five Chilean dairy manufacturers were selected as sources for post-consumer yogurt cups. In addition, cups containing labels, cups containing adhesive residues and clean cups were considered. FTIR-ATR combined with Principal Component Analysis (PCA) confirmed that post-consumer cups have a similar chemical structure and minimal food contamination. The polystyrene fractions in post-consumer cup waste exhibited a similar molecular weight distribution (Mn = 87–105 kDa and Mw = 230–280 kDa). According to TGA analysis, the adhesive residue and labels decrease the stability of post-consumer HIPS samples and contribute to the formation of stable carbon residues above 690°C. Al, Fe, Ti, Zn and Cr were quantified by ICP-MS. Zn (50–116 µg g ^− 1 ) was potentially related to the transformation of HIPS material into food packaging. Non-catalytic pyrolysis produced predominantly aromatic hydrocarbons (70–98% relative area), with styrene being the main compound. Cups containing labels yielded a broader range of products and minor oxygenated compounds, whereas cleaner cups showed higher styrene selectivity than virgin HIPS used as a reference. Overall, Chilean yogurt cup waste is a promising feedstock for producing styrene via non-catalytic cracking, although super clean methods are recommended beforehand.