Paint removal from recycled thermoplastic bumpers and its industrial revalorization in the automotive industry: application of shot blasting technology

The recycling and revalorization of polymeric waste is crucial to manage the large amount generated by the automotive industry. The most common recycling practice for thermoplastics materials is mechanical recycling, based on operations such as collect, separation of contaminations, washing/shredding, dying if required, tumbling with magnet, extrusion, palletisation and injection moulding (in case of exterior parts such as bumpers) [1]. During this process there are challenges that have not yet been solved. In the case of bumpers, superficial paint is observed on used or post-industrial bumpers that have had some defect in the painting process and are rejected. Paint residues negatively impact recycled plastics, creating weak points and compromising properties like thermal stability and mechanical strength [2]. Therefore, removing paint from polymeric waste, particularly bumpers, is crucial for obtaining high-quality recycled materials and a closed loop in automotive industry [3]. The study aims to use metal particle impact technology to efficiently remove acrylic paint from polypropylene substrate whit 20 % talc load in recycled bumpers. The main objectives of the work are (i) to observe the effect of the different test conditions on the effectiveness of removal paint, (ii) to make an approach to the industrial feasibility in a real recycling environment and (iii) to study different treatments for the elimination of the metallic particles left behind by the blasting process. The results show that the angular shot and a combination of 90°/grazing angle of incidence are better than the spherical shot and other angles. To remove these metal particles ultrasonic bath presents the best results among others, but a total elimination of these remains is not obtained.