薄膜加熱試験によるアスファルトの熱劣化の検討 (第2報)

劣化による組成及び解こう性の変化

抄録

The deterioration of Kuwait asphalt was studied by thin film oven test (TFO) and rolling thin film oven test (RTFO). The relationship between physical properties and chemical composition and that between penetration index (PI) and the peptization state of asphaltenes, and characteristics of deterioration in asphalt constituents were observed in an aging-process. The following results were obtained.
1) It was shown that the relationship of asphaltene content vs. reciprocal of penetration was linear in case of TFO, but that the plot was broken at about 25wt% of asphaltene content in case of RTFO. On the other hand, the linear relationship between the extinction coefficient of carbonic band and reciprocal of penetration was shown on both TFO and RTFO.
2) It was observed that penetration index decreased in the initial aging on both TFO and RTFO, while the state of peptization of asphaltenes increased. Therefore, the change of PI in the initial aging was mainly dependent on the change in the state of peptization of asphaltenes, but this relationship faild with the progress of deterioration.
3) From the results of chromatographic fractionation for asphalt constituents aged at 163°C for 20hr by TFO and the IR spectra, it was found that 6.2wt% of the saturates were changed to aromatics, 12.3wt% of the resins to asphaltenes, and 95wt% of the asphaltenes to insoluble materials in benzene, respectively and that the changes in composition of the aromatics and resins were mainly dependent on the molecular weight, but in case of the saturates it was dependent on the functional group containing oxygen. Therefore, the saturates molecule oxidized by heat was fractionated to the aromatics.