Preparation And Properties Of Modified Asphalt By Diisocyanate And Nanoclay

In recent years, the nanoclay modified asphalt is becoming a hotspot. With advantages of a unique layered structure, easy availability and low cost, nanoclay can significantly improve physical performance and anti-aging properties of base asphalt. Nanoclay is commonly dispersed in asphalt by high speed shearing, and reunion may occur during storage, transportation and application, thus affecting road performance, and chemical asphalt modifiers can effectively solve this problem.In this study, diisocyanate(such as isophorone diisocyanate(IPDI), diphenylmethane diisocyanate(MDI) and dicyclohexylmethane diisocyanate(HMDI)) which have two active-NCO groups were used to modify nanoclay(including sodium montmorillonite(Na-MMT), organic montmorillonite(OMMT) and expanded vermiculite(EVMT)). Moreover, modified nanoclays were used as chemical modifers to obtain diisocyanate/nanoclay modified asphalt materials by melt blending. The effects of diisocyanate type and reaction temperature on the modified nanoclays were studied, and Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD), scanning electron microscope(SEM) and thermogravimetry(TG) were used to characterize modified nanoclays. The results showed that, for the modification of Na-MMT, IPDI was best, the optimum reaction temperature was 85 ℃, and under this condition, one-NCO of IPDI reacted with-OH of Na-MMT while retaining the other end of the-NCO, layer spacing of IPDI-HMMT-85 was increased from 1.51 nm to 1.95 nm; for the modification of OMMT, HMDI was best, optimal reaction temperature was 80 ℃, the prepared HMDI-OMMT-80 was grafted with-NCO, layer spacing increased from 2.08 nm to 2.42 nm; for the modification of EVMT, HMDI was best, optimal reaction temperature was 80 ℃, the HMDI-EVMT-80 was not grafted with-NCO, layer spacing increased from 1.00 nm to 1.48 nm.Furthermore, the structure and properties of modified asphalt materials were studied by FT-IR, XRD, softening point, penetration, segregation experiments, UV aging test and TG te st. The results indicated that, the chemical modification of asphalt was achieved by the reaction of-NCO of IPDI-HMMT-85 and HMDI-OMMT-80 with hydroxyl of asphalt, with production of urethane, and exfoliated structure formed. And HMDI-EVMT-80 was physical blending with asphalt to form intercalated structure. Study on the properties of modified asphalt indicated that chemical modified asphalt is better than physical modified asphalt. IPDI-HMMT-85 modified asphalt, HMDI-OMMT-80 modified asphalt and HMDI-EVMT-80 modified asphalt of which segregation softening point difference was less than 2.2 ℃, had excellent storage stability; and physical properties and UV aging properties were significantly improved, with a softening point up to 62.2 ℃, changes of mass change rate, softening point increment and residual penetration ratio after UV aging were smaller than those of Na-MMT modified asphalt, OMMT modified asphalt and EVMT modified asphalt; and initial decomposition temperature of asphalt were increased from 354 ℃ to 363 ℃, 374 ℃ and 360 ℃, respectively, thermal stability were significantly enhanced. The performances of asphalt modified by modified nanoclays were significantly better than that of non-modified nanoclay.