衰减全反射红外光谱法的高密度聚乙烯自然老化特性研究

采用衰减全反射红外光谱技术(ATR-FTIR)研究物资储备中广泛使用的滚塑包装箱专用高密度聚乙烯(HDPE)，在特定湿热海洋环境的海南万宁实验站1年期内自然老化特性。定性分析老化前后化学结构变化，从断链、支化以及氧化角度区分不同阶段的老化特性，根据特征峰峰强和峰面积变化，定量分析羰基指数和相对结晶度的变化规律，探索老化前后羰基指数、相对结晶度变化与力学性能变化的相关性。结果表明：老化行为三个月内以断裂、支化为主，3~6个月氧化逐渐产生，6个月后氧化和支化占主导地位，9个月后氧化程度逐渐饱和，且老化进程与温度和辐照正相关。12个月后，羰基指数增长112倍，结晶度上升约10%，力学性能中材料拉伸/弯曲模量较拉伸/弯曲强度下降更快。老化前后羰基指数与拉伸模量变化相关系数为0.97，基于720~730 cm-1特征谱带计算的相对结晶度变化与拉伸强度变化相关系数为0.96。结果表明采用ATR-FTIR可以在快速无损检测的前提下，从老化前后化学结构的变化推测力学性能的变化。

Attenuated Total Reflection Infrared Spectroscopy for Degradation Profile of High Density Polyethylene after Weathering Aging

High density polyethylene (HDPE) was widely used as rotational packaging case in the material reserve field. The chemical changes of HDPE, exposed to particular climatic conditions of tropic marine atmosphere for one year-long in Wanning Hainan, were elucidated by the attenuated total reflection infrared spectroscopy (ATR-FTIR). The structural changes were studied qualitatively, mainly from the polymeric chain breaking, branching and oxidation to distinguish the degradation profile. The variations of crystallinity & carbonyl index were also studied quantitatively according to the characteristic peaks intensity & area ratio. Finally, the relationships between structural changes and mechanical properties were investigated. The results showed that the polymeric chain breaking & branching play a leading role before 3 months in the aging progress. Then oxidation phenomena gradually takes place during 3~6 months. The chain branching & oxidation were predominant factors after 6 months. Nine months later, the oxidation was saturated gradually. Furthermore, the aging process is positively correlated to the temperature and irradiation. After 12 months aging, the carbonyl index increased by 112 times and crystallinity was 10% higher than before. The tensile/bending modulus deceased faster than tensile/bending strength of HDPE. The linear degree of tensile modulus and carbonyl index was 0.97. The degree of linearity of tensile strength and crystallinity calculated by feature bands (720~730 cm-1) was 0.96. It showed that the mechanical properties of HDPE can be speculated from the structural changes by ATR-FTIR.