Study On The Synthesis And Applications Of The Polycarboxylic Water-reducing

Gypsum is a green building materials.It is a extensive resources of our country,so we have a unique advantage to develop gypsum.The polycarboxylic water-reducing is the key technologies to improve the performance of gypsum.This paper had prepared a novel polycarboxylic water-reducing by the method of radical polymerization,and studied the process of the preparation. Polycarboxylic water-reducing is made of co-polymerization reaction using monomers with functional group,such as sulfonic group;Polyoxyethylene etc,and study the influence of polycarboxylic water-reducing on the reduction rate of fluidity; Strength and the loss of fluidity in a period time of gypsum.The action mechanism of polycarboxylic water-reducing was discussed by the conductivity,the surface tension andthe adsorption,it is summarized as the following conclusion.1. Methoxy polyethylene glycol methacrylate-styrene polymer was synthesised through esterization.For p-toluenesulfonic acid,the optimum conditions for esterification are confirmed through single factor and orthogonal experiments.The esterification rate of 85.23% and the yield of 72.57% was obtained in10h,when the ratio of methacrylic acid to methoxy polyethylene glycol was 3.00:1.00, the dosage of the catalyst was 1%,the dosage of the inhibition was 2%.For PW₁₂/SiO₂,the optimum conditions for esterification are confirmed through single factor and orthogonal experiments.The esterification rate of 97.2% and the yield of 84.9% was obtained in 10h,when the ratio of methacrylic acid to methoxy polyethylene glycol was 3.00:1.00, the dosage of thecatalyst was 1%,the dosage of the inhibition was 1%. The characterization of PW₁₂/SiO₂ show that: PW₁₂/SiO₂ still retains the structure of Keggin,PW₁₂/SiO₂ still has a highly dispersion,and there is an obvious increase in the specific surface.The compared results showed that PW₁₂/SiO₂ is more suitable for the synthesis of methoxy polyethylene glycol methacrylate-styrene polymer.The copolymers were characterized with fourier transform infrared spectroscopy(FT-IR),1HNMR , and it shows that the product has the structure of methoxy polyethylene glycol methacrylate-styrene polymer.2. Polycarboxylic water-reducing was synthesised through radical polymerization using methyl polyglycolm ethacrylic acidester,propenoic-acid,1-(2-Methyl-2-propene) sulfonicacid sodium salt , ammonium persulfate .The impact of molar ratio of monomer, initiator, reaction temperature and polymerization time on the performance of polycarboxylic water-reducing was synthesised,the result shows that: ratio of monomer>reaction temperature> initiator> polymerization time.The optimum conditions for the reaction of polycarboxylic water-reducing are confirmed through single factor and orthogonal experiments.the optimal ratio was obtained in 3h at 90℃,when the ratio of 1-(2-Methyl-2-propene) sulfonicacid sodium salt to propenoic acid to methyl polyglycol methacrylic acid ester was 1.00:3.00:1.00,the dosage of the initiator was 2%.The product was characterized with fourier transform infrared spectroscopy(FT-IR) and GPC.It shows that the product has the structure of polycarboxylic water-reducing.The molecular weight of polycarboxylic water-reducing was 2.0×10⁴,the distributon of molecular weight is 1.88.3. The application performance of the polycarboxylic water-reducing which was used in the plaster was studied,then the comparison researches were done using same kind of water reducers on sell.The results show that the polycarboxylic water-reducing can improve the fluidity of fresh building gypsum paste and the strength of hardened building gypsum paste. Water-reducing rate of gypsum is higher than 21% and the strength of gypsum can be enhanced 100.59%.4. The action mechanism of polycarboxylic water-reducing was discussed in this paper.the adsorption of polycarboxylic water-reducing changes the structure and the electrochemical properties of gypsum particles.The chelating capacity and dispersion stability are enhanced by a variety of active groups in polycarboxylic water-reducing,and then the gypsum has a network structure,and this is a kind of polycarboxylic water-reducing for gypsum.