Synthesis and properties of viscosity-reducing polycarboxylate superplasticizer in continuous tubular reactor

A viscosity-reducing polycarboxylate superplasticizer VR-PCE-TR with a narrow molecular distribution was synthesized from thermally initiated reversible addition-fragmentation chain transfer (RAFT) polymerization of polyoxyethylene polyoxypropylene isopentenol ether (IPEPPG), 2-methyl-2-butylsulfanyl-thiocarbonylsulfanyl-propionic acid and maleic anhydride in a continuous tubular reactor, and characterized by 1HNMR, FTIR and GPC. VR-PCE-TR was then evaluated for its influence on the working performance and rheological properties of concrete, and for performance comparison with viscosity-reducing polycarboxylic acid superplasticizers prepared by conventional aqueous free radical polymerization in tank reactor. The results showed that, when the mass fraction of polycarboxylate superplasticizer solution was 10%, VR-PCE-TR exhibited the lowest surface tension (30.65 mN/m). When the superplasticizer mass fraction was 0.8%, VR-PCE-TR displayed a higher adsorption capacity for cement particles (2.803 mg/g). When the dosage (based on the mass of cement, the same below) of superplasticizer was 0.13%, the cement slurry with VR-PCE-TR showed better dispersion and dispersion retention performance, while when the dosage of superplasticizer was 0.4%, the cement slurry with VR-PCE-TR showed a lower yield stress (1.3 Pa) and lower plastic viscosity (0.26 Pa·s). The continuous tubular reactor avoided the material deoxygenation step and could maintain the polymerization control and polymerization reaction rate, therefore, the prepared VR-PCE-TR had a narrower relative molecular mass distribution (polydispersity index was 1.19), and thus had better viscosity reduction effect and application performance. © 2024 Fine Chemicals. All rights reserved.