研究了聚丙烯/有机改性蒙脱土(OMMT)纳米复合材料在365 nm紫外光辐照下的光氧化降解过程中的结构变化。 主要利用红外光谱方法进行表征。 在辐照初期(紫外光辐照时间小于11 h),复合体系的光氧化降解速率大于纯聚丙烯体系;随着辐照时间的延长(大于11 h),复合体系的光氧化降解速率小于纯聚丙烯体系。 主要原因是蒙脱土既有光屏蔽作用,又有加速光氧化降解的作用,这两种作用共存,但在辐照初期,催化光降解作用占主导地位,随着辐照时间延长,光屏蔽作用占主导。 蒙脱土的含量对聚丙烯的光氧化降解速率也存在影响。 另外,蒙脱土的加入对聚丙烯光氧化降解产物也产生影响,羧酸类及酸酐类产物增多,酯类产物减少。

Photooxidation degradation of polypropylene (PP)/organomontmorillonite (OMMT) nanocomposites was studied under UV irradiation at wavelength 365 nm. The OMMT was dispersed homogeneously in the PP matrix. The structural variation induced by photooxidation was detected by FTIR spectroscopy. It can be seen that the evolution of PP and nanocomposites PP/OMMT on irradiation is an increase in absorbance in the hydroxyl and carbonyl absorption regions. Carbonyl index was used to characterize the rate of photooxidative degradation. At the early stage of irradiation (shorter than 11 hours),the rate of photooxidative degradation of PP/OMMT nanocomposites was much faster than that of pure PP. With the increase in the irradiation time,the rate of photooxidative degradation of PP/OMMT nanocomposites became slower than that of pure PP. On the other hand,the OMMT content can also influence the photooxidative degradation rate. The variation in the photooxidative degradation rate is proposed to originate from the competition between the light shielding effect and accelerating photo-oxidative degradation effect of organomontmorillonite. These two effects play roles in the photooxidation process of PP simultaneously. At the early stage of irradiation,the accelerating photooxidative degradation effect dominates. With the increase in the irradiation time,the active sites such as SiOH, —OH etc and transition metal ions (Fe2+,Fe3+ etc) in the OMMT which can accelerate photooxidation are gradually consumed,and then the light shielding effect may play the main role. The method of curve-fitting was used to characterize the influence of organomontmorillonite on the photooxidative degradation products. Compared with pure PP,the content of products of carboxylic acid and anhydride were found to increase, whereas that of ester decreases in PP/OMMT nanocomposites.