聚羧酸减水剂的合成技术研究进展

2019,Vol.33,No.2

www.mater-rep.com

cshi@hnu.edu.cnDOI:10.11896/cldb.201903024 基金项目:国家重点研发计划(2017YFB0310100) ThisworkwasfinanciallysupportedbytheNationalKeyR&DProgramofChina(2017YFB0310100).

聚羧酸减水剂的合成技术研究进展

沙胜男,

史才军,向顺成,焦登武

湖南大学土木工程学院,绿色先进土木工程材料及应用技术湖南省重点实验室,长沙410082

由于聚羧酸减水剂(PCE)具有掺量低二减水率高(>40%)等特点,可显著改善混凝土的工作性能二力学性能和耐久性能,它已成为高性能或超高性能混凝土配合比设计中必不可少的组分之一三PCE通常由含阴离子基团(如羧基二磺酸基和磷酸酯基等)侧基的主链和中性接枝电荷的侧链组成,阴离子主要作为吸附基团吸附在带正电的水泥颗粒表面提供静电斥力,侧链提供空间排斥力,二者协同作用打破了水泥颗粒间的絮凝状态,改善了水泥浆体的分散性三各种各样(如侧链二接枝密度二锚定官能团和主链长度等)的改性PCE表现出不同的作用效果,可用于性能要求不同的混凝土三随着混凝土原材料的品质不断降低及性能要求不断提高,PCE对水泥类型二水灰比二操作温度二混合时间等混凝土配合比参数和生产条件更加敏感三由羧基和聚环氧乙烷(PEO)侧链组成的PCE与胶凝材料的不适应性越来越突出,超高性能混凝土对PCE的性能要求越来越高,一系列具有减缩二降粘二高保坍等性能的PCE应运而生三

PCE主要分为两类:一类是由α-甲氧基聚(乙二醇)甲基丙烯酸酯(MPEG-MA)通过水溶液自由基共聚或酯化/酯交换反应合成的聚酯型PCE;另一类是将α-烯丙基-α-甲氧基或β-羟基聚乙二醇醚和马来酸酐作为关键单体通过本体或水溶液自由基共聚,或是异戊二烯氧化聚乙二醇二丙烯酸和α-甲基丙烯酰-α-甲氧基或α-羟基聚乙二醇醚共聚合成聚醚型PCE三PCE中的不同官能团具有不同作用:羧酸基起减水和缓凝作用,磺酸基起分散作用,-OH羟基起缓凝和浸透润湿作用,而聚乙烷氧基类基团起保持流动性作用三酯类PCE的减水率及抑制水泥水化能力略低于醚类PCE三自由基聚合工艺简单二合成条件温和,但其因反应不可逆导致聚合度降低,合成产物难以控制;而活性自由基聚合(RAFT)可制备分子量可控二分子量分布窄的嵌段PCE三本文从原材料二合成条件二合成方法和后处理等方面综述了PCE合成制备技术的研究进展,并分析讨论了这些因素对PCE性能的影响,最后对PCE的发展趋势进行了展望三

关键词 聚羧酸系减水剂 合成方法 原材料 合成条件

中图分类号:TU528.042 文献标识码:A

TheState-of-the-artSynthesisTechniquesofPolycarboxylateSuperplasticizer

SHAShengnan,SHI

Caijun,XIANGShuncheng,JIAODengwuKeyLaboratoryforGreen&AdvancedCivilEngineeringMaterialsandApplicationTechnologyofHunanProvince,CollegeofCivilEngineering,HunanUniversi-ty,Changsha410082P

olycarboxylatesuperplasticizers(PCE)hasbecomeanindispensablecomponentofhigh-performanceorultra-highperformanceconcrete,owingtoitslowdosage,highwaterreducingrate(>40%),significantpositiveeffectsontheworkability,mechanical anddurabilityproper-tiesofconcrete.PCE.isusuallycomposedofabackbonecontaininganionicgroups(likecarboxyl group,sulfonicacidgroupandphosphategroup)andgraftedsidechainswithneutral charge.Theanionicgroupsareadsorbedonthesurfaceofcementparticles,providingtheelectrosta-ticrepulsionforces,whilethePEO-graftedsidechainsextendfromthecementparticlesurfaceintotheporesolutiontocreatesterichindranceforces.Thesynergisticeffectsofthetwoforcesbreakdowntheflocculatedclustersandimprovethedispersionofcementpaste.DiversemodifiedPCEwithdifferentsidechains,graftingdensity,anchoringfunctional groupandlengthofbackboneshowvariouseffectsandcanbeemployedbyconcretewithdifferentdemandinperformance.However,withthecontinuousraiseinrequirementsofconcreteperformanceandthedecreaseinqualityofrawmaterials,theperformanceofPCEmaybemoresensitivetothemixtureproportionparameters(cementtype,w/c,etc.)andpro-ductionconditionssuchasoperatingtemperatureandmixingtime.TheincompatibilitybetweenPCEwithcarboxyl andpolyethyleneoxide(PEO)sidechainsandcementitiousmaterialsisincreasinglyserious.Besides,withtheincreasingrequirementsofultra-highperformanceconcrete,ase-riesofPCEwithperformancesofshrinkagereduction,lowviscosityandhighslumpretentionhaveemergedasthetimesrequire. PCEcanbeprimarilyclassifiedintotwocategories.Oneispolyester-typePCE,whichmadefromα-methoxypoly(ethyleneglycol)methacry-lateester(MPEG-MA)byaqueousfreeradical copolymerizationoresterification/transesterificationreaction.Theotherispolyether-typePCE,whichissynthesizebyfreeradical copolymerizationinbulkorinaqueoussolutionwithα-allyl-α-methoxyorα-hydroxypoly(ethyleneglycol)(APEG)etherandmaleicanhydrideaskeymonomers,orcopolymerizationviaisoprenyl oxypoly(ethyleneglycol,acrylicacid,andα-methallyl-α-methoxyorα-hydroxypoly(ethyleneglycol)ether.Polycarboxylatesuperplasticizer(PCE)featureslowdosageandhighwaterreducingrate.Differentfunctional groupsofPCEexhibitdifferenteffects,forexample,carboxylicgroupsshowretardingeffectandwaterreducibility,sulfonicgroupsexertdispersingeffect,andhydroxyl groupsretardingandsoakingwettingeffects,andpolyethoxygroupspresentflowabilityretentionca-pability.Thewaterreducingrateandabilityofdelayedhydrationinhibitionofester-PCEareslightlylowerthanthatofether-PCE.Themethodoffreeradical polymerizationpossesseseasyprocessandmildsynthesisconditions,nevertheless,itisdifficulttocontrol thesyntheticproductsduetotheirreversiblereaction.Whilereversibleaddition-fragmentationchaintransfer(RAFT)polymerizationcanpreparetheblockPCEwithcontrolledmolecularweightandnarrowmolecularweightdistribution.Inthisarticle,thedevelopmentofsynthesistechniquesofPCEiscomprehensivelyre-viewedfromtheaspectsofrawmaterials,synthesisconditions,synthesismethodsandpost-processing.Theimpactsofthesefactorsontheper-formanceofPCEarediscussedindetail.Finally,thedevelopmenttrendofPCEisalsoproposed.

Keywords polycarboxylatesuperplasticizer,syntheticmethod,rawmaterials,synthesisconditions0 引言

减水剂已成为混凝土的重要组分之一,木质素磺酸盐最

先添加到水泥中发挥减水二缓凝作用三随后聚萘磺酸盐(PNS)二磺化三聚氰胺甲醛缩合物(PMS)二乙烯基共聚物二聚环氧乙烷(PEG)膦酸酯和聚羧酸醚(PCEs)相继应用到混凝土中三与木质素磺酸盐相比,PNS的减水率高,但PNS同某些水泥的不适应性导致坍落度损失快三与PNS相比,PMS的减水率与之相当,流动保持性略好,抑制水化能力较低三同PNS或PMS相比,乙烯基共聚物掺量减半,保坍性大幅提高,855万方数据

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