Applications of functionalized polyethylene terephthalate aerogels from plastic bottle waste

Abstract

Millions of tons of plastic are produced annually, but less than 10% are reported to be recycled. This work sets out to transform environmental plastic (polyethylene terephthalate - PET) waste into aerogels for high-value engineering applications, primarily to enhance the monetary incentive in recycling plastics. Coating techniques, using silicone ceramic (SCC) and (3-aminopropyl)triethoxysilane (APS, or APTES) solutions, are successfully devised to enhance the thermal stability and CO₂ adsorption capability of rPET aerogel. The rPET/SCC aerogel exhibits improved thermal stability (up to 600 °C), enhanced thermal insulation (thermal conductivity K_avg = [31.8-34.9] mW/m·K), hydrophobic characteristics (up to 144.7° in contact angle) and enhanced rigidity (Young modulus E_avg = [4.5-124.8] kPa), while maintaining an ultra-low density (ρ_a = [14-62] g/cm³) and a high porosity (Φ_avg = [95.6-99.0]%). Moreover, the amine-functionalised rPET aerogel achieves a CO₂ adsorption capacity of up to 0.44 mmol CO₂/g, superior to several commercial physio-sorbents. These promising results obtained demonstrate that the rPET aerogel is a versatile material suitable for a wide variety of high-value engineering applications, including thermal insulation and direct CO₂ capture applications.

Keywords: Adsorption; Flame retardant; Plastic aerogel; Polyethylene terephthalate; Thermal property.