聚羧酸高效减水剂结构与性能关系的研究

将丙烯酸、甲基丙烯磺酸钠和马来酸酐聚乙二醇单甲醚单酯通过自由基聚合,合成了聚羧酸高效减水剂,研究了减水剂结构与性能之间的关系,提出了聚羧酸高效减水剂的作用机理.     

聚羧酸系高效减水剂的合成及其作用机理研究

分析了聚羧酸系高效减水荆的结构与性能之间的关系，探讨了减水剂分子的主链结构单元与支链结构单元的功能与作用，并分类介绍了聚羧酸系的分子结构设计及其合成的研究与进展。结果表明，聚羧酸系减水剂的性能与其分子结构的主链和支链的结构单元、官能团的位置及其种类有关。在分子主链上引入大量合适大小分子量的聚乙二醇或聚氧乙烯接枝链和少量它们的嵌段链及一定构成比例的磺酸基团，可使减水剂在发挥低掺量高分散性的同时，产生良好的保塑性，且在合成过程中发现，聚氧烷基中的端羟基易引起凝胶。在此基础上结合原料的来源及其成本，选用聚乙二醇与丙烯酸在对甲苯磺酸作催化剂的条件下进行酯化，然后与甲基丙烯磺酸钠进行共聚，并加入一定量的丙烯酸单体来调节主链的大小及侧链上的羧基与磺酸基的相对构成比例，从而得到一种高性能减水剂。     

聚羧酸系高效减水剂PC的合成及性能研究

以甲基丙烯酸、聚乙二醇1000、对甲苯磺酸、对苯二酚、过硫酸铵和甲基丙烯磺酸钠为原料,采用两步法合成出新型聚羧酸系高效减水剂(简称PC)。将合成的PC与目前广泛使用的萘系高效减水剂(简称FDN)相比,具有更加优异的性能,具体表现为:在掺量很少情况下,水泥净浆就具有较高的流动度;当掺量相同时,其对水泥净浆流动度远超FDN。此外,它与水泥的相容性好,具有缓凝及明显抑制水泥净浆流动度经时损失性能,对混凝土也能表现出显著的减水增强性,是一种性能优良,适合于配制高强、超高强混凝土的高效减水剂。     

新型聚羧酸系混凝土高效减水剂的研制

简述了目前国内使用的减水剂存在的不足之处,并在实验室由马来酸酐、丙烯酰胺、甲基丙烯酸聚乙二醇酯等单体物质,在水溶液中经加热,并通过过硫酸胺引发共聚反应,制得聚羧酸系高效减水剂,并对其进行了性能测试,结果说明,该减水剂具有优良的分散能力和增强效果,保持流动性的时间较长;其分散性能和增强作用效果优于萘系高效减水剂。     

新型聚羧酸系混凝土高效减水剂的研制

简述了目前国内使用的减水剂存在的不足之处,并在实验室由马来酸酐、丙烯酰胺、甲基丙烯酸聚乙二醇酯等单体物质,在水溶液中经加热,并通过过硫酸胺引发共聚反应,制得聚羧酸系高效减水剂,并对其进行了性能测试,结果说明,该减水剂具有优良的分散能力和增强效果,保持流动性的时间较长;其分散性能和增强作用效果优于萘系高效减水剂.     

新型固体聚羧酸高效减水剂的研制

聚羧酸高效减水剂生产浓度一般为20%～40%（质量分数）,不宜储存和运输,限制了其更广泛的应用.利用本体聚合方法合成固体聚羧酸减水剂,在不加任何溶剂的情况下,利用原料中大单体TPEG、丙烯酸的物理化学特性,通过合适的引发剂（BPO）,实现反应原料熔融态下的聚合反应.最佳反应条件为TPEG∶AA∶MAS=0.8∶3.25∶0.4（摩尔比）,引发剂BPO用量为单体总质量的1%,反应温度为80℃,引发剂滴加时间为2h,保温时间为1.5h.反应结束后趁热将产物倒出,冷却至室温,经研磨成粉末,得到产品.实验得到的固体聚羧酸减水剂产品经研磨后无粘结现象,颗粒尺寸在0.125mm时,46s即可实现完全溶解,150d未出现变质结块现象.通过净浆试验和混凝土试验对产品进行了性能测试,结果表明产品性能超过了国内同类固体聚羧酸高效减水剂的产品水平.本体聚合法制备固体聚羧酸高效减水剂工艺简单、操作容易、对环境友好,具有非常广阔的工业前景.     

一种聚羧酸系高效减水剂的试验研究

主要研究以烯丙醇聚氧乙烯醚、丙烯酸、马来酸酐和甲基丙烯磺酸钠为主要原料的聚羧酸系减水剂的合成工艺,探讨了影响减水剂性能的各种因素,得到最佳工艺条件,并对减水剂的性能进行测试。结果表明,该聚羧酸减水剂具有低掺量、高分散性、高减水率等特点。在掺量为0.25%时,初始水泥净浆流动度达310 mm,减水率高达30.5%,混凝土的抗压强度得到大幅度的提高,适宜配制高性能混凝土。     

聚羧酸系高效减水剂的合成及机理研究

概述了聚羧酸系高效减水剂的研究进展和发展现状,讨论了聚羧酸系减水剂的合成方法、分子结构、分子结构与性能的关系以及其作用机理,并提出了聚羧酸系减水剂有待解决的问题及其研究发展趋势.     

多元聚羧酸高效减水剂的合成及性能研究

与传统减水剂相比,聚羧酸减水剂具有减水率和净浆流动度高及坍落度损失小等特性.基于分子结构设计理论和自由基聚合理论,以两种不同分子量的甲代烯丙基聚乙二醇(TPEG)为大单体,马来酸酐(MAn)、甲基丙烯磺酸钠(MAS)、丙烯酰胺(AM)等为小单体,在引发剂过硫酸铵(APS)的作用下多元共聚合成聚羧酸减水剂.系统地研究了反应温度,反应时间,引发剂和单体用量对减水剂净浆流动度、减水率、坍落度等性能的影响,并探讨了聚羧酸减水剂结构与性能之间的关系.结果表明:与普通聚醚类减水剂相比,该聚羧酸高效减水剂具有较高的净浆流动度、减水率、强度等.当减水剂掺量为0.5％时,其净浆流动度达到315 mm,而减水率可达35％.     

聚羧酸型高效减水剂的制备

采用多元共聚,通过实验优化,确定最佳原料配比及最优反应条件,合成一种新型聚羧酸高效减水剂.试验结果表明,该聚羧酸类高效减水剂对水泥具有高度的分散作用,掺加量为0.5%时,水泥净浆流动度可达214 mm,具有掺量低,减水率高,塌落度保持性好等优点.     

新型蔗糖基聚羧酸高效减水剂的合成与性能

以自制甲基丙烯酸蔗糖酯（MASE）、丙烯酸（AA）、甲基丙烯酸（MAA）、烯丙基磺酸钠和烯丙基聚乙二醇（A PEG ）为原料,以过硫酸钾为引发剂,自由基共聚法合成蔗糖基聚羧酸高效减水剂。研究了反应时间、蔗糖酯含量及引发剂用量对蔗糖基聚羧酸高效减水剂性能的影响。并通过流动度测试、红外光谱表征及黏度对减水剂的结构与性能进行了分析与比较。各组分物质的量nAA ：nMAA ：nSAS ：nAPEG ：nMASE ＝3∶1∶2∶1∶0．2,MASE含量为4．9wt．％,引发剂为单体用量1．9wt．％,反应时间为5h时合成的减水剂性能最好。在水灰比为0．29,折固掺量为0．3w t ．％,水泥净浆流动度达到340mm。     

早强型聚羧酸减水剂的合成及性能研究

以丙烯酸(AA)、异丁烯醇聚氧乙烯醚(HPEG)、甲基丙烯磺酸钠(SMAS)等为单体,分别采用丙烯酰胺(AM)、羟甲基丙烯酰胺(HAM)取代部分丙烯酸,通过水溶液聚合法制备出具有早强功能的聚羧酸系减水剂,并探讨了合成条件对水泥净浆流动度的影响.研究结果表明:在单体摩尔比n(AA)∶n(HPEG)∶n(SMAS)=4∶1∶0.36、反应温度为80℃、过硫酸铵(APS)用量为单体总质量的3%时,制备出的聚羧酸减水剂的分散性能较优.当AM取代为18%时,对提高混凝土的早期强度效果较佳,AM比HAM具有更好的早强效果.     

一种聚羧酸系减水剂的合成与性能

设计采用两步聚合法,即先通过一定分子质量的聚乙二醇(PEG)与丙烯酸(AA)在一定条件下发生酯化反应形成高分子大单体—聚乙二醇丙烯酸酯(PEGA),然后在水溶液中通过引发剂、PEGA和丙烯酸、甲基丙烯磺酸钠(MAS)发生共聚反应合成聚羧酸系减水剂.采用单因素变量试验法,分别研究了单体比例、引发剂用量、聚合温度、聚合时间及加料方式对聚合物性能的影响,从而得出合成聚羧酸系高性能减水剂的一种最佳工艺,并对试制产品进行了性能测试.结果表明:聚羧酸系减水剂具有优良的分散性能,能较长时间地保持水泥浆的流动性.     

Determination of residual monomers in polycarboxylate superplasticizer using high performance liquid chromatography

A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer (PCs) by reversed-phase high performance liquid chromatography (RP-HPLC).Four kinds of residual monomers were well separated and determined on a SinoChrom ODS-BP (C18) column with mobile phases composed of acetonitrile and phosphate buffer solution.The monomers were detected by UV detector at 205 nm and quantitatively analyzed with an external standard method.For those residual monomers,the linear response ranged from 4.0×10-6 mol·L-1 to 2.0×10-3 mol·L-1.The determination limit of acrylic acid,sodium methylallyl sulfonate and 2-Acrylamido-2-methylpropane sulfonic acid was 0.02×10-5 mol·L-1,while that of methoxy-polyethylene glycol monoacrylate was 0.1×10-5 mol·L-1.The relative standard deviation (RSD) of high concentration samples was less than 1%,while that of the low concentration samples was between 1%-4%.The standard (additional) recovery ratio was 97.4% -104.2%.     

The synthesis technique of polyacrylic acid superplasticizer

Using water separation technique,acrylic acid （AA） and polyethylene glycol （PEG） 1000,of which the ratio was 1.5,were esterified and the optimum esterification ratio of 90% could be reached under the condition of 110 ℃×3 h.Using polyoxyethylene acrylate macromonomer （PA） prepared in the esterification,AA and sodium methylacryl sulfonate （MAS） as monomers,a copolymer which could be used as superplasticizer was prepared by free radical coolymerization in n（PA）：n（AA）：n（MAS） of 1：7：3.When the synthesis condition was 80 ℃× 5 h,the optimal dosage of initiator was 3.0%-4.0%,the fluidity of cement paste with the samples could reach 270 mm.By analyzing the effect of the content of residual small molecule sulfonic monomer on the properties of sample,n（MAS）/n（PA） was controlled in a range of 2.5-3.8.     

Effects of molecular structure of polycarboxylate-type superplasticizer on the hydration properties of C3S

Effects of polycarboxylate-type superplasticizer(PC) molecular structure on the hydration heat of tricalcium silicate(C3S) paste and polymerization degree of hydration products(C-S-H gel) were researched by using TAM AIR isothermal microcalorimetry(TA) and 29Si nuclear magnetic resonance(NMR).Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.     

Effect of Molecular Structure on the Performance of Polyacrylic Acid Superplasticizer

The effects of structure parameters, such as molecular structure, segment kinds, molecular weight, and organic functional groups, on the performance of polyacrylic acid superplasticizer were discussed. According to the differences of chain sections, functional groups, eic, polyacrylic acid superplasticizer could be divided into A, B, C three parts. Among them, A chain section included sulfonic acid groups, B chain section carboxyl groups, C chain section polyester. Polyacrylic acid superplasticizers with different matching of A, B, C chain sections, different length of C chain section and different molecular weights were synthesized by acrylic acid, polyethylene glycol, sodium methyl allylsulfonate; the relation between the molecular structure and perfolxnance was also studied. The expetimental results indicate that the water-reduction ratio increases obviously with the increment of the proportion of sodium methyl allylsulfonate chain section in the molecular; the slump retention increases greatly with the increment of the proportion of acrylic acid chain section; the dispersion of cement particles increases with the increment of the chain length of polyethylene glycol; when the molecular weight is in the range of 5000, the dispersion and slump retentibity increase with the increment of the average molecular weight of polymers.     

Influences of soluble salts on adsorption properties of polycarboxylate superplasticizers

Polycarboxylate(PC) superplasticizers with different chemical structures were synthesized through free radical co-polymerization reaction.A total organic carbon analyzer was used to investigate adsorption behaviors of PCs,and to evaluate influences of soluble salts on absorption properties of PCs.It is found that adsorption ratios of PCs on cement particles decrease greatly with the addition of Na2SO4;the adsorption ratio of ethers PC with Hydroxyethyl methacrylate(HEMA) group first increases then decreases with the addition of NaCl;the adsorption ratio of esters PC with short side chains first decreases then increases,while the adsorption ratio of ethers PC with HEMA group decreases with the addition of CaCl2;the adsorption ratio of esters PC with short side chains decreases with the addition of Ca(NO3)2;AlCl3 causes the decrease of the adsorption ratio of ethers PC with HEMA group.