Zhou Li-juan, Zhang Xiu-qin, Zhao Ying, Yang Ming-shu, Wang Du-jin, Xu Duan-fu
Beijing National Laboratory for Molecular Sciences, Chinese Academy of Sciences Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2010 Oct;30(10):2671-5.
The degradation behavior of polypropylene and polypropylene/stabilizer composites, caused by gamma radiation, was studied in the present work The stabilizers used were hindered phenol antioxidant and hindered amine light stabilizer. FTIR spectroscopy and DSC analysis were used to determine the structural variation induced by gamma radiation. It can be seen that the evolution of PP and composites PP/stabilizers on gamma irradiation is an increase in absorbance in the hydroxyl and carbonyl absorption regions. Carbonyl index calculated from FTIR spectra was used to characterize the rate of degradation. When the irradiation dose was small (<50 kGy), the degradation of pure polypropylene and polypropylene/stabilizers composites was not obvious; while the irradiation dose increased (> or =50 kGy), the carbonyl indexes of all the samples increased obviously, and the degradation degree of polypropylene/stabilizer composites was bigger than pure polypropylene. This result might be partially attributed to the molecular chain scission of hindered phenol and hindered amine under larger irradiation dose. The chain scission of stabilizers forms hydroperoxides and peroxide radicals, catalyzing the degradation of polypropylene. As the irradiation dose was small (<50 kGy), the crystallization temperatures of pure polypropylene and polypropylene/stabilizer composites all showed no remarkable changes; as the irradiation dose exceeded 50 kGy, the crystallization temperatures of pure polypropylene and polypropylene/stabilizer composites all decreased obviously. Correspondingly, the melting peaks of both pure polypropylene and polypropylene/stabilizer composites moved to lower temperature and split into two peaks with increasing the irradiation dose. The decrease of crystallization and melting temperatures might be attributed to the destruction of chemical structure and stereo-regularity of the molecular chain, due to the increasing of carbonyl and hydroxyl groups brought by the oxidation of polypropylene molecular chain. At the same irradiation dose (> or = 50 kGy), the crystallization and melting temperatures of polypropylene/stabilizer composites were lower than that of pure polypropylene. It indicates that the stabilizers accelerate the degradation of polypropylene. The results were accordant with the IR results.
本工作研究了γ辐射引起的聚丙烯及聚丙烯/稳定剂复合材料的降解行为。所用稳定剂为受阻酚抗氧剂和受阻胺光稳定剂。采用傅里叶变换红外光谱（FTIR）和差示扫描量热法（DSC）分析来确定γ辐射引起的结构变化。可以看出，γ辐射下聚丙烯及其复合材料的演变是羟基和羰基吸收区域吸光度增加。由FTIR光谱计算得到的羰基指数用于表征降解速率。当辐照剂量较小时（<50 kGy），纯聚丙烯和聚丙烯/稳定剂复合材料的降解不明显；而当辐照剂量增加（≥50 kGy）时，所有样品的羰基指数均明显增加，且聚丙烯/稳定剂复合材料的降解程度大于纯聚丙烯。该结果可能部分归因于较大辐照剂量下受阻酚和受阻胺的分子链断裂。稳定剂的链断裂形成氢过氧化物和过氧自由基，催化聚丙烯的降解。当辐照剂量较小时（<50 kGy），纯聚丙烯和聚丙烯/稳定剂复合材料的结晶温度均无明显变化；当辐照剂量超过50 kGy时，纯聚丙烯和聚丙烯/稳定剂复合材料的结晶温度均明显降低。相应地，随着辐照剂量增加，纯聚丙烯和聚丙烯/稳定剂复合材料的熔融峰均向低温移动并分裂为两个峰。结晶温度和熔融温度的降低可能归因于聚丙烯分子链氧化带来的羰基和羟基增加导致分子链化学结构和立构规整性的破坏。在相同辐照剂量（≥50 kGy）下，聚丙烯/稳定剂复合材料的结晶温度和熔融温度低于纯聚丙烯。这表明稳定剂加速了聚丙烯的降解。结果与红外分析结果一致。
