Abstract: 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.

Key words: foam, ultraviolet aging, mechanical properties, chromatography, oxidation, degradation

摘要： 采用紫外加速老化方法,研究聚苯乙烯泡沫(EPS)在受到紫外老化后其外观和缓冲性能的变化规律,分析材料内部结构的变化.结果表明,随着加速紫外老化时间的延长,EPS分子链上产生某种显色基团,导致试样表面颜色变黄,EPS的最小缓冲系数值增大,缓冲效率降低;且随老化时间的增加,EPS分子量降低,分子量分布由2.13增大到3.76;分子结构中C元素含量减少,O元素含量逐渐增加,紫外线照射导致EPS表面受到激发并在水和热的共同作用下发生表面氧化,生成C O键、C—OH键等新的官能团;加速老化使EPS结构中大分子断链,化学键重组,导致力学性能下降.研究EPS材料的老化行为是推断其使用寿命和环境的基本依据,为EPS衬垫在运输包装过程中的合理应用提供参考依据.

关键词: 泡沫, 紫外老化, 力学性能, 色谱, 氧化, 降解