The variation of external appearance and cushioning properties of expanded polystyrene (EPS) was investigated and the change in internal structure of EPS was analyzed by using the ultraviolet (UV) accelerated aging method. The physical properties and chemical structure of EPS before and after aging were determined by colorimetric analysis

mechanical properties test

gel permeation chromatography (GPC)

X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR/FTIR). With increasing time of UV accelerated aging

on the molecular chain of EPS some coloring groups that turned the color of the sample surface yellow were produced. With increasing aging time

minimum cushioning coefficient value increased

and cushioning efficiency decreased. When aging time was more than 100 h

growth rate of cushioning coefficient had a significant rise

and there was a tendency to lose cushioning property. With increasing aging time

molecular weight of EPS decreased

and molecular weight distribution increased from 2.13 to 3.76

indicating photo-oxidative degradation. So stability of molecular structure of EPS was destroyed. C element content decreased and O element content increased gradually in molecular structure of EPS. UV irradiation excited EPS surface

and oxidation occurred under the interaction of water and temperature to generate new functional groups

such as C O

C—OH bonds. Accelerated aging broke macromolecular chain to reorganize chemical bond in EPS structure

resulting in the decline of mechanical properties. The aging behavior of EPS is the fundamental basis to determine service life and service environment. It provides a reference for the reasonable application of EPS liner in transport packaging processes.