Chemiluminescence studies on the photooxidation of isotactic polypropylene
Chemiluminescence studies on the photooxidation of isotactic polypropylene
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DOI：
10.1016/j.polymdegradstab.2021.109575
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发表时间：
2021-04-23
影响因子：
5.9
通讯作者：
Yamada, Rie
中科院分区：
文献类型：
--
作者：
Hosoda, Satoru;Sato, Tetsu;Yamada, Rie
采用化学发光法研究了室温下聚丙烯（PP）在254 nm和365 nm紫外光照射下的光氧化反应。根据照射后的CL强度变化的动力学分析，求出UV照射停止时的CL强度（I（t=0））。I（t=0）的辐照时间依赖性给出了一个时间过程，其中CL强度在第一阶段随时间增加并达到稳定状态，并在保持相同水平一段时间后，在后期大幅增加。稳态强度，这被认为是过氧自由基形成的速率，被认为是依赖于PP的结晶度。结晶度越低，稳态强度越高，表明光引发反应优先发生在非晶相中。在高于熔点的样品，这是存储在25摄氏度的紫外线照射后的各个时期的等温CL测量表明，有两种类型的CL发射源的不同的寿命;一个是淬火在约一天，其他生存超过10天。温升测量也表明存在两种类型的CL发射源。此外，发现在UV照射之前的热氧化明显促进光氧化。相比之下，在氧气中的热氧化越来越加速的预光氧化。(C)2021爱思唯尔有限公司版权所有。
Photooxidation of polypropylene (PP) was investigated by chemiluminescence (CL) after UV irradiation of main wavelengths of 254 nm and 365 nm in air at an ambient temperature. From the kinetic analysis of CL intensity change just after irradiation, CL intensity at the time of the cessation of UV irradiation, (I(t=0)), was obtained. The irradiation time dependence of I(t=0) gave a time-course, where the CL intensity increased with time in the first stage and reached a steady state, and after maintaining the same level for a while, it largely increased in the later stage. The steady state intensity, which is considered the rate of peroxy radical formation, was found to be dependent on the crystallinity of PP. The lower the crystallinity is, the higher the steady state intensity is, indicating the preferential photoinitiation reaction to occur in the amorphous phase. The isothermal CL measurement at above the melting point of the samples, which were stored at 25 degrees C for various periods after UV irradiation, suggests that there are two types of CL emitting sources of different lifetimes; one is quenched in about one day and the other survives for more than 10 days. The temperature rising measurement also indicates the existence of two types of CL emitting sources, too. Further, thermal oxidation before UV irradiation was found to clearly promote the photooxidation. In contrast, thermal oxidation in oxygen was increasingly accelerated by the pre-photooxidation. (C) 2021 Elsevier Ltd. All rights reserved.