Understanding microwave interactions with polymers to enable advanced plastic chemical recycling

Abstract

The widespread adoption of plastics has led to substantial production and waste generation, raising environmental concerns. Chemical recycling offers a promising solution to enhance recycling rates, with microwave heating emerging as an attractive technology for polymer breakdown. This paper investigates the dielectric properties of various polymers and their temperature dependencies, providing insight into the effectiveness of microwave heating. Results indicate that while polymers may show low dielectric loss at room temperature, those with polar segments exhibit increasing loss at high temperatures, indicating that additional susceptors may not always necessary for effective microwave heating. Three key transitions are identified with respect to their significant impact on the dielectric properties of polymers at elevated temperatures: the glass transition temperature, the decomposition temperature, and the point where the dispersion/displacement peak exceeds the measurement frequency. Additionally, this paper introduces a new approach for utilising microwave heating for the selective, multistage recycling of mixed plastics.

Keywords

• Dielectric properties
• Polymers
• Plastic chemical recycling
• Microwave heating
• Pyrolysis