Study On Hyperbranched Polycarboxylate Superplasticizer

Compared with other types of water reducing agent,polycarboxylate superplasticizer(PCE)has advantages of low dosage,high water reducing ratio and environment friendly,thus it has become the mostly researched and used water reducing agent.Hyperbranched polymers becomes one of research hotspot in macromolecule field duo to its special structure,property and potential application prospect.This research combines PCE with hyperbranched polymer and designs PCE molecule structure,aiming to enhance the water-reducing performance of PCE.Firstly,the synthesis of PCE was studied.By using methylallylpoly oxygenethene ether 2400(HPEG 2400)and propenoic acid(AA)as raw material,ammonium persulfate(APS)as initator and 3-thiohydroxypropanoic acid as chain transfer agent,PCE was synthesized through free radical polymerization in aqueous solutions.With cement paste fluidity as performance measurement index,the influence of initator dosage,chain transfer agent dosage,monomer ratios,reaction temperature and reaction time on the performance of PCE were investigated.The optimize conditions for PCE synthesis were APS dosage 0.5 wt%,3-thiohydroxypropanoic acid dosage 0.2 wt%,the mole ratio of HPEG 2400 to AA of 1: 3.5,reaction temperature 50 oC,reaction time 4 h.PCE synthesized under these conditions has good dispersing effect to cement paste and cement paste fluidity is up to 310 mm.Secondly,hyperbranced monomer was searched and synthesized through many experiments.With Diallylamine,methyl propenoate and trihydroxymethylpropane as raw material,a hyperbranched monomer B was successfully synthesized.Characterizations for this hyperbranched monomer B were performed,i.e.Fourier infrared spectrum and 1H Nuclear magnetic resonance.The results show that the structure of hyperbranched monomer B is the same as expected.Finally,hyperbranched PCE was successfully synthesized based on optimize conditions for PCE synthesis with HPEG,AA and B as raw material.Mole ratios of these monomers were mainly investigated.According to the experiments,the proper mole ratio of HPEG to B and AA of 3: 2: 15.Hyperbranched PCE synthesized under these conditions has good dispersing effect to cement paste and cement paste fluidity is up to 320 mm.The molecular weight of hyperbranched PCE was determined by gel permeation chromatography.The result shows that number-average molecular weight and weight-average molecular weight are 23393 and 34671 g/mol,respectively.