Photodegradation behavior and mechanism of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers: correlation with copolymer composition
Photodegradation behavior and mechanism of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers: correlation with copolymer composition
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DOI：
10.1039/c6ra21985c
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发表时间：
2016-01-01
期刊：
影响因子：
3.9
通讯作者：
You, Hongjun
中科院分区：
文献类型：
--
作者：
Chen, Tingting;Zhang, Jun;You, Hongjun
首次研究了不同1，4-环己二醇二甲醇(CHDM)含量的聚(乙二醇-1，4-环己二醇二甲基对苯二甲酸酯)无规共聚物(PETG)的组成对其光降解行为的影响及其机理。用X射线光电子能谱(XPS)和衰减全反射傅里叶变换红外光谱(ATR-FTIR)表征了紫外光辐照后PETG共聚物表面化学基团的变化。用差示扫描量热法(DSC)和热重分析法(TGA)研究了紫外光辐照前后PETG共聚物的热性能。通过测定凝胶含量来评价紫外光辐照后PETG共聚物的交联度。PETG共聚物的光氧化速率随CHDM含量的增加而增大。也就是说，PETG共聚物的固有光稳定性随着CHDM含量的增加而降低。不同组成的PETG共聚物具有相似的光氧化机理。PETG分子链中CHDM的存在加速了光产物的形成。PETG共聚物的光产物由脂肪醇、酸酐、苯甲酸、双键和末端的脂肪酸以及分子对苯二甲酸组成。此外，在整个辐照过程中(0-800h)，紫外光照射产生的交联物不会进一步氧化。紫外光辐照后，共聚物的玻璃化转变温度(T(G)S)因辐照交联剂的作用而升高。随着CHDM含量的增加，T-g的增量逐渐增大。因此，CHDM含量越高，得到的交联度越高。
The effect of copolymer composition on the photodegradation behavior and the mechanism of poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG) random copolymers with different 1,4-cyclohexanedimethanol (CHDM) content were first investigated. The changes in surface chemical groups of the PETG copolymers after UV irradiation were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform-infrared (ATR-FTIR) spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to probe the thermal properties of the PETG copolymers before and after UV irradiation. The crosslinking degree of the PETG copolymers after UV irradiation was evaluated by gel content measurement. The photooxidation rate of the PETG copolymers increased with increasing CHDM content. Namely, the inherent photostability of the PETG copolymers decreased with increasing CHDM content. The PETG copolymers with different compositions exhibited the similar photooxidation mechanism. The presence of CHDM in the PETG molecular chains accelerated the formation of photoproducts. The photoproducts of the PETG copolymers were consisted of aliphatic alcohol, anhydride, benzoic acid, double bond and aliphatic acid as end-groups and molecular terephthalic acid. Moreover, the crosslinking products formed during UV irradiation were not further oxidized in the whole irradiation period (0-800 h). The glass transition temperatures (T(g)s) of the PETG copolymers after UV irradiation increased due to the irradiation crosslinking. The increment of T-g increased gradually with increasing CHDM content. Therefore, the higher the CHDM content was, the higher the crosslinking degree obtained.