紫外老化对沥青化学组成与分子结构的影响

Effect of Ultraviolet Aging on Chemical Composition and Molecular Structure of Asphalt

为研究紫外老化对沥青微观结构的影响,通过对4种沥青分别进行4组分、红外光谱和核磁共振等试验,研究紫外老化下沥青的4组分、特征峰、官能团等化学组成指标和氢谱图、碳谱图、氢原子含量、分子结构参数等分子结构指标的变化,并通过分子结构指标对化学组成指标的表征,分析分子结构变化对沥青化学组成变化的影响。结果表明:紫外老化后沥青更趋于形成沥青质分子,而沥青质的转化来源主要为芳香分,且含量越高老化后的损失率越高;同时羰基和亚砜基会随着老化的时间增加先快速增加之后趋于平缓,其中羰基指数可表征沥青老化的产生,而亚砜基指数可评价沥青抗老化的能力。紫外老化下沥青芳香环会发生缩合程度增大、环烷基取代基增加以及氢的取代、结构异化等反应;同时高紫外光子能量也会使脂肪碳发生断键,断键的脂肪碳连接到芳香环上提高了化学稳定性。由表征分析可见,沥青的化学组成主要受芳香结构、支化度和芳香环系缩合指数的影响较大。

To determine the influence of ultraviolet(UV)aging on the microstructure of asphalt.The four-component,infrared spectrum,and nuclear magnetic resonance tests on four kinds of asphalt respectively were conducted,and the changes of the four components,characteristic peak,functional group and molecular structure indexes of asphalt under ultraviolet aging were investigated as well,such as hydrogen spectrum,carbon spectrum,hydrogen content,molecular structure parameters and other molecular structure indexes.The influence of molecular structure change on the chemical composition of asphalt was analyzed through the characterization of the molecular structure index to the chemical composition index.The results show that asphaltene molecules tend to form after ultraviolet aging,and the asphaltene conversion source is mainly aromatic fraction.The fact is founded that the higher the content of asphaltene,the higher the loss rate after aging is.Meanwhile,the carbonyl group and sulfoxide group increase rapidly first and then flatten out with the aging time.The carbonyl group index can represent the aging of asphalt,while the sulfoxide group index can evaluate the anti-aging ability of asphalt.Under ultraviolet aging,the degree of condensation,the increase of cycloalkyl substituents,the substitution of hydrogen,and the structure dissimilation of the asphalt aromatic ring occur.At the same time,a high UV photon energy can also cause fatty carbon to break bonds,which can improve the chemical stability of the fatty carbon connected to the aromatic ring.It can be seen from the characterization analysis that the chemical composition of asphalt is mainly affected by the aromatic structure,branching degree,and condensation index of the aromatic ring system.