Effect of the ratio of carboxyl group to ethylene oxide on performance of acrylic acid based copolymer scale inhibitors

Abstract

In this paper, a novel new monomer Allyloxy Vinyloxy carboxylic acid (APEA) is obtained by carboxymethylation and chloroacrylation using polyethylene glycol (PEG-600), chloroacetic acid and sodium hydroxide as raw materials. After that, four hydrophilic copolymers AA-APEA with different carboxyl to ethylene oxide ratios were prepared by free radical copolymerisation of APEA and acrylic acid (AA) as monomers and its structure is elucidated using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance hydrogen spectrum (1H NMR). Subsequently, the effects of the ratio of carboxyl group to ethylene oxide on performance of AA-APEA are evaluated in terms of dosage, Ca2+ concentration, temperature, inhibition time and pH value by static experiments. The impacts of the polymer on formation of CaCO3 are investigated using scanning electronic microscopy (SEM) and X-ray single crystal diffraction (XRD). In addition, the binding energy of AA-APEA to the surface of calcium scale and iron crystals was investigated using molecular dynamics (MD) simulation. Then, the results indicate that the increase of the ratio of carboxyl group to ethylene oxide has a positive effect on the anti-calcium-scale property of AA-APEA. SEM and XRD analysis reveal that AA-APEA significantly changes the surface morphology of CaCO3 scale, destroys the crystal structure of CaCO3 scale. The binding energy of the polymer molecules to the calcium scale and Fe surface increases with increasing carboxyl to ethylene oxide ratio.

Keywords

• Carboxyl
• Anti-scaling mechanism
• Ethylene oxide
• Molecular dynamics