Research On Synthesis And Performance Of Polymaleic Anhydride Superplasticizer

Polycarboxylate superplasticizer has an important role on the improvement of concrete performance,it has been widely used at present.Among in which,as a result of a better solution to loss of concrete slump,Polymaleic Anhydride Superplasticizer is one of the important direction on research and application at the moment.But in the synthesis process of Polymaleic Anhydride Superplasticizer,it exist these problems below.First,macromer with polymerization activity is not easy preparated.Second,the effects of polymerization conditions on ternary copolymerization is not clear.Third, the effects of the proportion of each group in polymerization product on superplasticizer performance is not clear.In response to the issues above,we carried out the work of the following three aspects:(1) To acrylic acid(AA),polyethylene glycol(PEG) and methoxy polyethylene glycol(MPEG)as raw materials,we preparates macromer with polymerization activity by esterification,investigates synthesis conditions and factors which impact on the properties of macromer.Based on these experimental results,esterification reaction conditions have the same effects on esterification by different terminal group of PEG.;the performance of macromer containing diester preparated by the esterification of PEG and AA,is worse than that preparated by the esterification of MPEG and AA.(2) To maleic anhydride(MA),sodium methyl-acrylamide(MAS) and macromer preparated by the esterification of MPEG and AA as raw materials,we preparates Polymaleic Anhydride Superplasticizer by ternary copolymerization,investigates the effect of polymerization conditions on the structure and properties of polymerization products.Based on these experimental results,as the polymerization temperature increasing,fluidity of cement paste of superplasticizer and the molecular weight of polymer product increase at first and then decrease;As the polymerization time increasing,fluidity of cement paste of superplasticizer increases at first and then stabilizes gradually,and the molecular weight of polymer product remains basically unchanged;As the concentration of initiator increasing,fluidity of cement paste of superplasticizer increases at first and then decreases,and the molecular weight of polymer product decreases all along.(3) we preparates acrylic block of Superplasticizer Polymaleic Anhydride with different proportion of functional groups,by changing the ratio of monomers, investigates the effect of the changes of each group proportion on properties of polymerization products.Based on these experimental results,As the proportion of—SO₃^- increasing,the role of chain transfer enhanced,the fluidity of cement paste of superplasticizer increases at first and then decreases;As the proportion of macromer increasing,the role of the steric hindrance of polymerization product enhanced,the fluidity of cement paste of superplasticizer increases at first and then decreases too.When the mole fraction of MA between 0.5 and 0.65,the mole fraction of MAS between 0.05 and 0.15,the mole fraction of macromer between 0.3 and 0.35,the molecular weight of MPEG is 1000,polymerization products obtain the best performance of fluidity of cement paste.When the content of superplasticizer is 0.2%,water-cement ratio is 0.29,the fluidity of cement paste reach at 307mm,At this point the molecular weight of polymerization product is 1.28×10⁴.