Odour characterisation of high-density polyethylene recycled with sepiolite by sensory evaluation

In recent years, the production and consumption of plastics has increased. This growth in production has resulted in an increasing amount of plastic waste, which is a global problem. Among plastics, high density polyethylene (HDPE) is one of the most widely used polymers in the packaging industry, so its waste is used in the recycling process. One of the main disadvantages of accepting recycled HDPE in production processes is its odour, which makes it impossible to use in production lines. The aim of this work is to reduce and/or eliminate the odours present in the HDPE samples selected for recycling through the use of sepiolites. FTIR analysis of the HDPE samples sent for recycling showed the presence of small amounts of polypropylene (PP), (PET), flexible polyurethane, dirt and adhesives, which could be the cause of the bad odour. Washing the sample showed a decrease in odour, probably due to the removal of dirt and other products that can lead to the degradation of the plastics responsible for the odour. The characterisation of the mixture of sepiolites and HDPE aims to analyse the mechanical and thermal stability of the sample. Not only can pre-washing lead to odour reduction, but also extrusion and injection processes at elevated temperatures can lead to the removal of volatile or semi-volatile compounds. Sensory analysis showed a reduction in odour in HDPE samples with sepiolites, particularly with 15% Pensil sepiolite, to the detriment of mechanical stability. At lower concentrations of sepiolite, the results are good from a sensory, mechanical and thermal point of view, which could mean an industrial application in the manufacture of benches, flower pots, etc.