Prevention Strategy of Cement Slurry Sedimentation under High Temperature. Part 1: A Polymer with Continuous Thermo-Thickening Behavior from 48 to 148 °C

Traditional thermoresponsive polymers with amphiphilicity exhibit acute thermo-thickening behaviors through phase transition and cannot be used as stabilizer to prevent high-viscosity liquid from viscosity reduction versus increasing temperature. Therefore, this study aims to develop a water-soluble polymer that has both thickening ability and continuous thermo-thickening ability in a wide temperature range. Inspired by the researches about hydrophobically associating polymers, a novel thermo-thickening polymer with strong hydrophobicity (HTP) has been synthesized, which consists of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and a hydrophobic monomer with surfactant character (SHM). HTP has good thermal stability and moderate resistance to the salt and alkali. In particular, HTP exhibits a continuous thermo-thickening behavior from 48 to 148 °C and can mitigate the consistency reduction of cement slurry under high temperatures. A series of experimental results (including environmental scanning electron microscope, gel permeation chromatography, differential scanning calorimeter, and pyrene fluorescence probe) indicate that the microstructure changes of HTP molecules in solution determine the thickening and thermo-thickening behaviors of HTP. The thickening behavior of HTP is due to the generation of spatial molecular networks in solution. The formed networks become more tangled and larger along with increasing HTP concentration resulting in a higher viscosity of solution. Under higher temperature, the tangled HTP molecular chains may stretch and fabricate much larger and denser networks causing the thermo-thickening behavior of HTP. It is hoped that the thermo-thickening polymer presented in this paper can be applied in various fields.