The pyrolysis mechanism analysis of polystyrene and phenol–formaldehyde resin microplastics using mass spectrometry

As a new pollutant, microplastics (MPs) have characteristics such as environmental persistence, biological toxicity, bioaccumulation and so on, even at low concentrations in the nature. At present, the detection methods for MPs are still in the development stage, and mass spectrometry (MS) is one of the most effective methods for microplastic detection and analysis. This paper utilizes a self-developed temperature programmed system pyrolysis (Py) device and a time of flight mass spectrometer (TOFMS) to establish a Py-PI-TOFMS using a single photon ionization (PI) source, and to construct an analysis technology for microplastics. The pyrolysis of thermoplastic MPs mainly follows the free radical pyrolysis mechanism, where the energy obtained through heating reaches the bond energy connected between atoms, and the molecular chains undergo fracture to generate various small molecule compounds. We used Py-PI-TOFMS technology to analyze the pyrolysis products of microplastics of polystyrene (PS) and phenol–formaldehyde resin (PF), explore the rules of free radical reactions, composition of pyrolysis products, bond dissociation characteristics, and combine theoretical calculations to study the thermodynamic and kinetic mechanisms in the pyrolysis process.