Investigation in the pyrolysis of polyester coated on aluminum-based beverage: Thermodynamic properties, product and mechanism

Aluminum cans are typical solid waste. Polyester coatings not only polluted the environment, but also affected the quality of aluminum recycling. In this study, three common local polyester coatings on the surface of aluminum cans were selected as raw materials (PC-PB, PC-VY and PC-SG). Thermogravimetric analysis, elemental analysis, Fourier transform infrared spectrometer and pyrolysis gas chromatography/mass spectrometry (PY-GC/MS) were used to study the pyrolysis behavior and pyrolysis products of the polymer components coated on the aluminum cans. TG analysis showed that pyrolysis of the coatings mainly occurred at 250–540 °C, with a weight loss of about 25 % for the polyester coating PC-PB and PC-VG, and a lower weight loss of 15 % for polyester coating PC-SY. The effect of pyrolysis temperature on the pyrolysis products of polyester coatings was investigated using PY-GC/MS. The results showed that the main products of pyrolysis included four major groups: oxygenated compounds, aromatic compounds, nitrogenous compounds and aliphatic hydrocarbons. At 600 °C, the aromatic compounds, oxide-containing reached 57–67 % and 20–27 %, respectively. The main pyrolysis products include neopentyl glycol, phthalic anhydride, toluene, styrene and so on. The high content of aromatic compounds in the product can be used as chemical raw materials as well as alternative fuels. In addition, the pyrolysis principles of the three main components of polyester coatings (polyester resins, amino resins, and styrene-acrylic resins) were postulated.