Modification of bitumen emulsion via heterocoagulation with SIS triblock copolymer latex

Bitumen emulsions have often been modified by styrene-butadiene rubber latex. The modified bitumen can have excellent low-temperature cracking resistance, but rutting resistance at high temperature still remains poor. In the current work, for the first time, a stable poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer latex is synthesized by reversible addition-fragmentation transfer (RAFT) emulsion polymerization. Based on this, a simple heterocoagulation process is developed to prepare the bitumen emulsions modified by SIS. The heterocoagulation results in hybrid particles of SIS shell and bitumen core. With addition of 5 wt % SIS, a continuous polymer-rich phase could be formed in the modified bitumen once the modified emulsion was broken down. The bitumen modified by 5 wt % SIS shows a significant increase in complex modulus at high temperature and a significant decrease in loss tangent, suggesting excellent resistance to rutting at high temperature, which is consistent with the significant increase in softening point from 41 degrees C for the base bitumen up to 64 degrees C. Meanwhile, the ductility at 5 degrees C of the modified bitumen is also dramatically increased from 1.4cm for the base bitumen to 40cm, indicating the low-temperature cracking resistance should also be much enhanced. (c) 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45510.