A Dual-Functional Polymeric Cationic Emulsifier for Emulsification and Modification of Emulsified Asphalt

Conventional cationic emulsified asphalt materials prepared from small-molecule emulsifiers are deficient in low-temperature ductility and adhesion. Polymer-based emulsifiers hold promise for overcoming this technical challenge. This study developed a novel polymer-based cationic asphalt emulsifier (M-PCAE) using methyl oleate (MO), maleic anhydride (MA), 4-methylphenylene (4-MP), and tetraethylenepentamine (TEPA) as raw materials. The surface activity, ζ-potential, active matter content, and temperature sensitivity of M-PCAE and three small-molecule cationic asphalt emulsifiers (SCAE) were analyzed. The optimal component ratio was determined, and the preparation process parameters were optimized. The storage stability and low- and high-temperature performance of the emulsified asphalt were also evaluated. Experimental results indicate that MO, MA, and 4-MP first polymerize to form the backbone chain, subsequently undergo amidation with TEPA, and finally dehydrate intramolecularly at high temperatures to form the imidazoline ring. M-PCAE exhibits significantly superior surface activity and electrostatic stability, which is closely related to its high active substance content. M-PCAE also has a low glass transition temperature and a high initial decomposition temperature, whereas SCAEs form solid crystals at low temperatures and are prone to decomposition. Appropriate amounts of MA, TEPA, and 4-MP are beneficial for emulsifying characteristics, micelle stability, and thermostability, but they slightly impair the low-temperature deformability. Considering the overall properties of M-PCAE, the optimal molar ratio of MO, MA, TEPA and 4-MP is determined to be 1.0:0.7:1.36:0.4. Excessively high stirring speeds can reduce polymerization efficiency, and the amidation temperature should be controlled to prevent premature molecular dehydration. Furthermore, M-PCAE endows emulsified asphalt with excellent short-term and long-term storage stability, while simultaneously enhancing its low- and high-temperature performance.