جستجوی مقالات مرتبط با کلیدواژه « ابرروان کنند ه » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Different macromonomers having polyethylene glycol branches were synthesized via esterification reactions in various conditions. Quaternary polymers were prepared using synthesized macromonomers of polyoxyethylene acrylate and methacrylate with a PEG molecular weight of 600-3000 g/mol, and sodium acrylate, sodium methacrylate and sodium maleate. The superplasticizers were synthesized by free radical polymerization in water medium at 65-80oC. The recipe and polymerization conditions have a direct effect on the structure of superplasticizers. The structures of the synthesized quaternary polymers were characterized by 1H NMR, Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) analyses. The efficiency of a superplasticizer depends on the size of main chain, the chemical structure of repeating unit, molar ratio of monomers, chain-to-ion molar ratio (B/I) and size of the branches. These structural parameters affect the geometrical restriction, adsorption and the interaction between the superplasticizer chains and cement particles. FTIR, thermal gravimetric analysis (TGA) and X-ray powder diffraction (XRD) methods were also used to characterize the effect of superplasticizer structure on the hydration reaction of the cement pastes. FTIR spectroscopy was used to explore the effect of superplasticizer structure such as branch length and chain-to-ion molar ratios on the structure of the hydrated calcium silicate gels, polysilicate (SiO4-2) and calcium hydroxide generated during 7 days hydration. The results of XRD indicated that the structure of superplasticizer affects the content of anhydrous phase and hydrated products during hydration. The increase of PEG branch length slightly increased the decomposition temperatures of the hydrated calcium silicate gels and calcium hydroxide crystals. Furthermore, the size of calcium hydroxide crystals changed with the superplasticizer branch size.