Synthesis Of Modified Sodium Carboxymethylcellulose Polymers And Its Application In Cement Mortars

The synthesis of ternary-graft-copolymer of sodium carboxymethylcellulose-g-poly (the monomer of sulfo group)/poly (the monomer of ester group) emulsion was carried out by potassium persulfate induced graft copolymerization in homogeneous aqueous medium. Fourier transforms infrared spectra was used for studing both of monomers modifications and graft to sodium carboxymethylcellulose. The synthesis of polymers contain cellulose ether, sulfo group, carboxyl and ester group. All these functional groups play a part in modification of cement mortars. The polymers was used scanning electron microscope, X-ray diffraction and thermal gravity analysis for structure characterization. The micromorphology of cement mortars could be observed by scanning electron microscope.Three kinds of modified CMC polymers emulsion were synthesized by experiment. And the polymers emulsion were applied in cement mortars, the properties of cement mortars were improved obviously.The result of cement mortars were modified by synthesis of sodium carboxymethylcellulose-g-poly (sodium p-styrenesulfonate)/poly (butyl methacrylate) emulsion:Under the condition of water reducing20%, when the dosage of the CMC-g-PSS/PBMA is1.5%, The cement mortars obtain the best compressive property. When the graft copolymer is2.5%, The cement mortars obtain the best flexural property. In order to obtain the sample of compressive property and flexural property are improved at the same time, The sodium lignosulfonate should be put into the sample of the graft copolymer is1.5%for Intensifying its dispersing property and the Tributyl phosphate should be put into this sample for controlling the air entrained volume, the effect is obvious.The result of cement mortars were modified by sodium carboxymethylcellulose-g-poly (sodium p-styrenesulfonate)/poly (methyl methacrylate) emulsion:Under the condition of water reducing25%, the sodium lignosulfonate should be put into the sample of the dosage of the CMC-g-PSS/PMMA is1.5%for Intensifying its dispersing property and the Tributyl phosphate should be put into this sample for controlling the air entrained volume, the mechanical properties of cement mortars were improved obviously. The curing of modified samples after7days the flexural strength was increased of7.99%, the compressive strength was increased of25.60%. The curing of modified samples after28days the flexural strength was increased of8.26%, the compressive strength was increased of24.04%.The result of cement mortars were modified by sodium carboxymethylcellulose-g-poly (sodium methylallyl sulfonate)/poly (methyl methacrylate) emulsion:Under the condition of water reducing7.2%, when the dosage of the CMC-g-PSMAS/PMMA is0.03%, the air content is4.9%, The curing of samples after7days the flexural strength was increased of6.12%, the compressive strength was lost of4.13%. The curing of samples after28days the flexural strength was increased of6.59%, the compressive strength was lost of4.52%. the relative dynamic and elastic modulus is71.03%after300times freeze-thaw cycle. The advantage of CMC-g-PSMAS/PMMA:high solubility, excellent chemical stability, little loss of the strength, excellent property of air-entraining and excellent resistance to freezing and thawing in cement materials. Comprehensive evaluation revealed that this air-entraining agent was a new one with high performance and worthy of popularization in concrete construction.