Photodegradation mechanism of PEF

Polyethylene 2,5-furandicarboxylate (PEF), as an emerging bio-based polymer, has attracted widespread attention due to its environmentally friendly properties. The photodegradation mechanism is one of the important pathways for PEF degradation, which mainly triggers chemical reactions through light radiation, resulting in changes in the physical and chemical properties of the material.
The photodegradation of PEF is mainly due to the action of ultraviolet (UV) radiation. The energy of ultraviolet light is high enough to break the chemical bonds in the PEF molecular chain, especially the ester bonds. This cleavage reaction produces free radicals, which further trigger a series of chain reactions. The photodegradation process can be divided into the following stages:
Light absorption: When PEF is exposed to UV radiation, specific chemical bonds in the molecule absorb light energy and are excited to a higher energy state.
Chain scission: The absorbed energy causes the ester bonds in the molecular chain to break, forming low molecular weight compounds and free radicals.
Oxidation reaction: The generated free radicals react with the surrounding oxygen molecules to form peroxides, which further promote chain scission and cross-linking reactions.
Photodegradation products
The photodegradation products of PEF mainly include short-chain polymers and small molecular organic matter. The formation of these degradation products will affect the mechanical properties and optical properties of the material. Studies have shown that photodegradation can cause color changes and decreased transparency of PEF, reflecting the deterioration of its physical properties.
The rate of photodegradation is affected by a variety of factors, including:
Light source intensity and wavelength: Different wavelengths of UV radiation have different effects on PEF degradation, and the UV-C band (200-280 nm) generally has the greatest impact on degradation.
Environmental conditions: Environmental factors such as temperature, humidity, and oxygen concentration can affect the degradation process. For example, high humidity can promote hydrolysis, further accelerating degradation.
Additives: Certain light stabilizers and antioxidants can be added to PEF to improve its light stability and slow down the degradation rate.