Synthesis And Application Of Multi-branched Polycarboxylate Superplasticizer

The water reducer has good dispersibility and dispersion retention performance in cement.Therefore,it has become the most and the largest used in cement admixture.In recent years,the demand for cement and the performance requirements of products have been gradually improved,so the performance requirements of water reducing agents have also been improved.In this paper,polycarboxylate superplasticizer with different multi-branched structures were synthesized by two different polymerization methods.And the effect of different structure of polycarboxylate superplasticizer on its properties was also studied.1.In this paper,the reversible addition-fragmentation chain transfer polymerization(RAFT)was used to synthesize polycarboxylate superplasticizer with a definite molecular structure.Firstly,a macromolecular chain transfer agent with multi-branched structure was synthesized by using maltodextrin as core.Then,a multi-branched block polycarboxylate superplasticizer(MBBPCE)was successfully prepared by RAFT polymerization of acrylic acid(AA)and prenyl alcohol polyoxyethylene ether(TPEG).The effects of the amount of chain transfer agent,monomer molar ratio and different block structure on the dispersion of MBBPCE were investigated,and the optimal ratio of MBBPCE was obtained,n(AA): n(TPEG): n(AIBN): n(CTA)= 55.6 : 11.12 : 1: 0.25.The target product was successfully prepared by IR spectrum and GPC gel chromatography analysis.2.Using maltodextrin as core and polycarboxylic acid as branched chain,multi-branched random polycarboxylate superplasticizer(MBRPCE)was successfully synthesized by one-step method.First,Ceric ammonium nitrate(CAN)was used to oxidize the hydroxyl groups of maltodextrin to form free radicals,and then acrylic acid(AA)and prenyl alcohol polyoxyethylene ether(TPEG)was initiated to polymerization.The effects of the molar ratio of carboxyl group to polyether group,the degree of polymerization of polyether and different kinds of polyether on the properties of MBRPCE were studied.We obtained that the optimum experimental ratio for the preparation of MBRPCE was n(maltodextrin): n(CAN): n(AA): n(TPEG 2400)= 1 : 8.2 : 318 : 68.IR spectrum analysis showed that the water reducing agent was successfully prepared.3.The multi-branched polycarboxylate superplasticizer prepared by the two methods was tested by fluidity of cement paste,and the results showed that the two kinds of polycarboxylate superplasticizer had better water reducing effect.On this basis,the surface tension,adsorption behaviors and properties of MBRPCE in cement paste and mortar were also studied.MBRPCE has a high water-reducing rate and good dispersion performance in cement mortar,and can also effectively improve the strength of cement mortar test block.At the same time,MBRPCE also has a good mud resistance.Compared with commercially available comb-type polycarboxylate superplasticizer,MBRPCE has better fluidity and flow retention performance of cement paste.