Recycled polyethylene terephthalate and aluminum anodizing sludge-based boards with flame resistance

The objective of this study was to utilize polyethylene terephthalate (PET) and aluminum anodizing sludge (AAS) to produce fire-resistant polyurethane (PU) boards of different densities. Boards with 10%, 20%, 30%, 40% and 50% PET waste as a replacement for the PU raw material were prepared with the addition of 20% aluminum sludge. The products were checked by scanning electron microscopy (SEM) to show that the addition of residues modified the morphology of the alveoli and reduced the compressive strength of the rigid foams. The boards showed combustion deceleration up to flame extinction in the flammability test (UL94) because of the presence of the AAS. The influence of the fillers on the combustion of the specimens without and with 50% PET was observed through SEM images of the preserved and burnt regions of the materials. A reduction in the direct production costs of all the sheets was measured and reached close to 70% in the case of the board with the highest amount of added residues. Therefore, as a way to save natural resources and become more sustainable, it is suggested that the civil construction industry consider the addition of these residues as part of its formulations.