Modifying bitumen emulsions with 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 a work, a stable poly(styrene-b-isoprene-b-styrene) (SIS) triblock copolymer latex was synthesised by reversible addition-fragmentation transfer (RAFT) emulsion polymerisation. Based on this, a simple heterocoagulation process was developed to prepare the bitumen emulsions modified by SIS.
Improved cracking resistance
The heterocoagulation resulted in hybrid particles of SIS shell and bitumen core. With addition of 5 wt % SIS, a continuous polymer-rich phase could be formed once the modified emulsion was broken down. The modified bitumen showed 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 °C for the base bitumen up to 64 °C. Meanwhile, the ductility at 5 °C of the modified bitumen was also dramatically increased from 1.4 cm for the base bitumen to 40 cm, indicating the low-temperature cracking resistance should also be much enhanced.
The study is published in: Applied Polymer Science, Volume 134, Issue 48, December 20, 2017.
