Synthesis And Properties Of A Four Arm Polycarboxylate Superplasticizer

With the rapid development of modern building construction technology,people have put forward higher requirements on the performance of concrete,corresponding the performance requirements of the water reducer has gradually increased,the traditional comb like polycarboxylate superplasticizer can’t meet the requirements of high performance concrete.Moreover,the traditional comb like polycarboxylate superplasticizer is a random copolymer,and its molecular structure is not clear,so it can not reveal the relationship between structure and properties.Therefore,using atom transfer radical polymerization method to synthesize a kind of controllable four arm AB type double block polycarboxylate superplasticizer in order to make up for the deficiency of comb like polycarboxylate superplasticizer in this study.This topic with pentaerythritol(PET)as core and tert butyl acrylate(tBA),methyl allyl alcohol polyoxyethylene ether(TPEG)as monomer,Pentamethyldiethylenetriamine(PMDETA)as the ligand,copper bromide(CuBr)as catalyst,using the method of atom transfer radical polymerization to synthesize a kind of four arm AB double block polycarboxylate superplasticizer FAPC.The optimum experimental conditions were as follows: the ratio of each material: n(pentaerythritol): n(BIBB): n(tBA): n(TPEG)=1 : 4.2 : 143 : 25,n(initiator): n(CuBr): n(PMDETA)=1 : 4 : 8;Other experimental conditions:(1)Preparation of small molecular initiators: Under the condition of ice water bath(0 ℃),adding Alpha bromo benzoyl bromide(BIBB)to pentaerythritol,the dropping time is 1 hours.After the addition,raise the temperature to room temperature to react 24 hour.(2)Preparation of PtBA,P(tBA-TPEG): the reaction temperature is 85 ℃,reaction time is 18 h.(3)hydrolysis reaction: the volume ratio of trifluoroacetic acid to water was 9 : 1,the reaction time was 10 h.The synthesized FAPC was characterized by IR spectrum,surface tension,apparent adsorption capacity and Zeta potential;Discuss the effects of the amount of pentaerythritol,alpha-bromo-bromo bromide,tert butyl acrylate and methyl allyl polyoxyethylene ether and molecular weight,type on the properties of FAPC.In order to further evaluate the performance of the synthesized FAPC,compared the performance of FAPC and ZD,the results showed that FAPC is superior to ZD in terms of several aspects including the dispersion of slurry,the dispersion of mortar,the water reducing ratio,the resistance to mud,the applicability of the cement and the mechanical properties of the mortar.