Study on the Polymerization Process and Monomer Reactivity of EPEG‐type Polycarboxylate Superplasticizer

In this study, the binary aqueous free radical copolymerization process of ethylene-glycol monovinyl polyethylene glycol (EPEG) and acrylic acid (AA) was studied. The influence of monomer type and molar ratio on the conversion ratio of EPEG and the molar ratio of copolymer were investigated via gel permeation chromatography (GPC) by comparing the macromonomer molecular structures, side chain densities, and carboxyl group concentrations. According to the results, the reactivity of EPEG copolymerized with AA was higher than that of isoprenyl oxypoly (ethylene glycol) ether (IPEG, also referred to as TPEG) with AA. The copolymerization reaction between EPEG and AA could be completed within 30 min at 10-20 degrees C. At the initial stage, the copolymer content quickly attained 60% within 15 min, reflecting the short induction period and high chain propagation rate constant. The fluidity tests in cement mortar revealed that polycarboxylate superplasticizers (PCEs) with short side chains and high conversion ratio exhibited better dispersion capacity than PCEs with long side chains.