The influence of dispersant structure on its dispersibility performance

R groups (polymer chains): The most common R groups are polyisobutylene (PIB). The molecularweight (Mn) of the polymer has a significant impact on dispersibility. Both excessivelyhigh and low molecular weights are not conducive to dispersibility, hence, themolecular weight of dispersants is typically concentrated between 3000-7000.Higher molecular weights have a positive effect on improving dispersibility,but overly long chains can affect low-temperature properties, which requires acomprehensive consideration. Additionally, the polydispersity index (PDI, i.e.,Mw/Mn) is also an important parameter for assessing the dispersibilitycharacteristics of PIB. A lower PDI indicates that the polymerization degree ofthe polymer is closer to that of a pure substance, resulting in betterdispersibility.

Anchor groups: Conventional dispersants usually have one anchor group, whiledouble-hang dispersants have two. The role of the anchor group is similar tothe handle of a broom, stabilizing the broom head in front, and it has asignificant impact on dispersibility. For example, Mannich base dispersants areobtained through the Mannich reaction, which replaces maleic anhydride as theconnecting body, possessing a certain polarity, but not too strong.

Polar ends: Thepolar end is the core part of the dispersant, with common polar ends includingpolyethylene polyamines. Since sludge or oxidation products are usually acidic,dispersants containing N (alkaline) help adsorb these substances. Differentpolar ends have a significant difference in selectivity for differentsubstances, therefore, different types of engines require different types ofdispersants.

In summary, the dispersibility ofdispersants is closely related to the molecular weight of their R groups,polydispersity index, anchor groups, and the structure of the polar ends. Thesefactors collectively determine the performance of dispersants, which in turnaffects their dispersing effects in different applications.