Synthesis of core–shell soap-free emulsion and evaluation of its performance in oil-well cement

A soap-free latex (XY-5) was prepared by means of a soap-free emulsion free-radical polymerisation method, using the synthetic polymer P (BA/AANa) as an emulsifier and butyl acrylate (BA), styrene and methyl methacrylate as monomers. The stability, thermal stability and microstructure of the XY-5 emulsion were studied using various methods, including viscosity analysis, zeta potential measurement, thermogravimetric analysis and transmission electron microscopy. The emulsion was found to have high stability and good heat resistance, with the latex particles exhibiting a typical core–shell structure. Its performance as an oil-well cement was also evaluated. The results showed that the XY-5–cement slurry has good temperature resistance, salt resistance, low water loss and low permeability. Furthermore, the use of XY-5 effectively improved the cementation strength. Scanning electron microscopy showed that the XY-5 latex forms a three-dimensional network structure inside the cement, with cement particles linked together by latex particles. The comprehensive performance of XY-5 latex was found to be much better than the THD-815 latex on the market.