Xu Xiong, Yu Jianying, Xue Lihui, Zhang Canlin, Zha Yagang, Gu Yi
State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China.
Center for Materials Research and Analysis, Wuhan University of Technology, Wuhan 430070, China.
Materials (Basel). 2017 Jul 7;10(7):768. doi: 10.3390/ma10070768.
Tri-block copolymer styrene-butadiene (SBS) is extensively applied in bituminous highway construction due to its high elasticity and excellent weather resistance. With the extension of time, tri-block structural SBS automatically degrades into bi-block structural SB- with some terminal oxygen-containing groups under the comprehensive effects of light, heat, oxygen, etc. In this paper, the effects of aging temperature, aging time and oxygen concentration on the molecular structure of thermo-oxidative aged SBS were mainly investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and the correlation between oxygen-containing groups and thermal properties (TG-DTG) was further discussed. The FTIR and XPS results show that rapid decomposition of SBS will occur with increments of aging temperature, aging time and oxygen concentration, and a large number of oxygen-containing groups such as -OH, C=O, -COOH, etc. will be formed during thermo-oxidative aging. In short-term aging, changes in aging temperature and oxygen concentration have a significant impact on the structural damage of SBS. However, in long-term aging, it has no further effect on the molecular structure of SBS or on increasing oxygen concentration. The TG and DTG results indicate that the concentration of substances with low molecular weight gradually increases with the improvement of the degree of aging of the SBS, while the initial decomposition rate increases at the beginning of thermal weightlessness and the decomposition rate slows down in comparison with neat SBS. From the relation between the XPS and TG results, it can be seen that the initial thermal stability of SBS rapidly reduces as the relative concentration of the oxygen-containing groups accumulates around 3%, while the maximum decomposition temperature slowly decreases when the relative concentration of the oxygen-containing groups is more than 3%, due to the difficult damage to strong bonds on the molecular structure of aged SBS.
三嵌段共聚物苯乙烯 - 丁二烯（SBS）因其高弹性和优异的耐候性而广泛应用于沥青公路建设中。随着时间的延长，在光、热、氧等综合作用下，三嵌段结构的SBS会自动降解为带有一些末端含氧基团的双嵌段结构SB - 。本文主要利用傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）研究了老化温度、老化时间和氧浓度对热氧化老化SBS分子结构的影响，并进一步探讨了含氧基团与热性能（TG - DTG）之间的相关性。FTIR和XPS结果表明，随着老化温度、老化时间和氧浓度的增加，SBS会迅速分解，在热氧化老化过程中会形成大量的含氧基团，如 -OH、C = O、-COOH等。在短期老化中，老化温度和氧浓度的变化对SBS的结构破坏有显著影响。然而，在长期老化中，它对SBS的分子结构或增加氧浓度没有进一步影响。TG和DTG结果表明，随着SBS老化程度的提高，低分子量物质的浓度逐渐增加，而热失重开始时的初始分解速率增加，与纯SBS相比分解速率减慢。从XPS和TG结果的关系可以看出，当含氧基团的相对浓度在3%左右积累时，SBS的初始热稳定性迅速降低，而当含氧基团的相对浓度超过3%时，最大分解温度缓慢下降，这是由于老化SBS分子结构上的强键难以破坏。
