Synthesis And Properties Of The Maleimide-Structural Polycarboxylic Superplasticizer

In this paper, a series of maleic anhydride-structural polycarboxylic superplasticizers were prepared according to the chararcteristics of molecular structure of polycarboxylic superplasticizers, and the molecule frame of the chemical structure of superplasticizers were designed and optimized. The superplasticizers were inculed two sisytems:one of them was polmaleic anhydride-structural superplasticizer that was prepared with maleic anhydride as polymerization monomer and different hydrophilic chain; the other of them was maleimide-structural superplasticizer that was prepared with maleimide and tranditional monomer. The work performance of tow sisytems and the action mechanism of maleimide-structural superplasticizer was investigated.Polmaleic anhydride-structural superplasticizer includes styrene-maleic anhydride grafted sucrose(SAMSUE) and styrene-maleic anhydride grafted polyethylene glycol(SAMPEG). Its were prepared from 1-(chloromethyl)-4-ethenyl-benzen(CSt), maleic anhydride(MAH), sucrose(SUE) and polyethylene glycol(PEG). The molecular structure was characterized. Effects of the reaction conditions on the initial fluidity were investigated. The result shows that SAMSUE and SAMPEG prepared under optimal condition have good plasticizing, the initial fluidity of cement paste reaches 320mm and 285mm, and the water-reducing ratio is 27.9% and 26.3% with the dosage is 0.3 wt% accoeding to the mass.The monomer of maleimide-structural superplasticizer includes N-carbamoyl maleimide(NCM), N-carbamoylmaleamic aicd(NCMA) and N-methoxypolyethylene glycols-N-carbamoyl maleimide(MPNCM). Its were prepared with MAH, carbamide(Urea) and methoxypolyethylene glycols(MPEG). The molecular structure was characterized.Maleimide-structural superplasticizer includes MAH-sodium methylallyl sulfonate-MPNCM(MSM), acrylic acid-SMAS-MPNCM(MSA) and NCMA-SMAS-polyethylene glycol monoallyl ether(NSA). They were prepared from MAH, sodium methylallyl sulfonate(SMAS), acrylic acid(AA), polyethylene glycol monoallyl ether(APEG) and MPNCM. The molecular structure of superplasticizers was characterized by FI-IR and 1H-NMR. Effects of reaction condition on initial fluidity were investigated with initial fluidity as measurement index. The result shows that the MSM, MSA and NSA prepared under optimal condition has good plasticizing, the water-reducing ratios are 26.6%,27.7% and 25.7%, the initial fluidities of cement paste reaches 288mm with the 0.2wt% according to the mass.The action mechanism of maleimide-structural superplasticizer was investigated with Zeta potential and adsorption of MSN, MSA and NSA. The result shows that the mechanism of the superplasticizer was mainly owing to that the electrostatic interaction and complexation between the cationic groups and anionic groups of the superplasticizer and the surface of cement particles, when the superplasticizer was in contact with the surface of cement particle. The Zeta potential of the surface of cement particle was changed. The electric double layer was developed between the superplasticizer and the surface of cement particles It made cement particles remain stable and improved the fluidity of cement paste, which the action of electrostatic repulsion between different cement particles.