Development of sustainable ceramic floor tiles using eco-friendly binders derived from plastic wastes through chemical recycling

Abstract

The accumulation of plastic waste, particularly polyethylene terephthalate (PET), presents a growing environmental threat due to its non-biodegradable nature and limited recycling efficiency using conventional methods. This research explored a sustainable solution by chemically recycling PET plastic waste into monomers and integrating them as binding agents in ceramic floor tile production. Two chemical recycling techniques, glycolysis and ammonolysis, were used to depolymerize PET wastes into monomers of Bis(2-hydroxyethyl) terephthalate (BHET) and terephthalamide derivatives, respectively. Monomers were incorporated in clay to form clay-based ceramic tiles using a fixed clay mass of 200 g and varying monomer volumes of 50, 60, 70, 80 and 90 ml. The key properties such as thermal conductivity, water absorption, density, specific gravity, flexural strength, and compressive strength were carried out on tiles according to relevant ASTM and ISO standards. To further understand the structural integration and chemical composition of the tiles, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy with Energy dispersive X-ray spectroscopy (SEM/EDX) were also conducted. SEM images displayed a more compact and homogenous microstructure in tiles produced using glycolyzed PET monomers, while EDX analysis confirmed the elemental composition, including the distribution of Si, Al, Fe, and traces of carbon indicative of monomer integration. These findings provided insight into the microstructural and molecular interactions between the recycled PET waste monomers and ceramic components. Results indicated that tiles made using glycolysis-based monomers exhibited better mechanical and thermal properties than those from ammonolysis, with compressive strengths reaching 34.25 MPa and flexural strengths exceeding 14 MPa at optimal monomer volume. Water absorption rates declined with increasing monomer content, indicating reduced porosity and improved structural integrity.