Improving the aging resistance of styrene-butadiene-styrene tri-block copolymer modified asphalt by addition of antioxidants

The aging properties of base asphalt and styrene-butadiene-styrene tri-block copolymer (SBS) modified asphalts (PMA) are evaluated using Fourier Transform Infrared (FTIR) spectroscopy. An aging cell fitted to the FTIR microscope was used to continually and directly study the oxidation of the PMA. In particular, Attenuated Total Reflectance, ATR, with a zinc selenide prism was used to quantify the changes in the spectra of the PMA before and after thin film oven test (TFOT). The effect of a small amount (1 wt%) of some modifiers, zinc dialkyldithiophosphate (ZDDP), zinc dibutyl dithiocarbamate (ZDBC) or naphthenoid oil, on the chemical and physical properties of the PMA was studied. The modification extent of the modifiers increases in the order: oil, ZDBC, ZDDP. With the aging of the PMA, carbonyl groups formed and the intensity of the absorption peak at 965 cm−1 (the characteristic peak of SBS) decreased. Antioxidants, ZDDP or ZDBC modified PMA are resistant to the formation of carbonyl to some extent, indicating the improvement of aging resistance of the PMA by the addition of the antioxidants. ZDDP and ZDBC as antioxidants can retard the oxidation of the PMA through the inhibition of peroxides and radical scavenging. Furthermore, ZDDP in a liquid state at room temperature acts as plasticiser, giving rise to a good aging resistance of PMA.