蒙脱土对聚羧酸减水剂的吸附特性及其影响因素研究

采用凝胶渗透色谱法研究了蒙脱土对聚羧酸减水剂( PCE)的吸附平衡及其影响因素。结果表明,蒙脱土对PCE具有很强的吸附作用,PCE浓度越大,其吸附量也越大。当PCE浓度为2.00 g·L-1(混凝土中PCE标准掺量)时,其吸附量为7.03 mg·g-1;当PCE为4.00 g·L-1时,其吸附量为14.61 mg·g-1;蒙脱土对PCE的最大吸附量(饱和吸附)约为21.18 mg·g-1。当PCE浓度≤2.50 g·L-1,体系pH值的变化对吸附量影响不大,但Ca2+、Mg2+金属离子的存在会增大PCE吸附量,其中Mg2+离子的影响尤为明显。蒙脱土吸附PCE是一吸热过程反应,过程符合准二级动力学方程,平衡仅需5~10 min。     

侧链结构对聚羧酸盐减水剂性能的影响

以丙烯酸、甲氧基聚乙二醇丙烯酸酯、烯丙基磺酸钠为原料,分别制备引入羧基侧链、引入聚氧乙烯侧链以及同时引入羧基与聚氧乙烯侧链的聚羧酸减水剂.加入水泥净浆性能测试结果表明,羧基侧链对减水剂的分散性能影响较大,聚氧乙烯侧链对减水剂的保塑性能影响较大,同时具有两种侧链的减水剂的分散性能和保塑性能都得到提高.     

季铵盐对聚羧酸减水剂在水泥-蒙脱土表面吸附的影响

采用紫外标记技术对聚羧酸分子的紫外吸收进行增强,进而采用紫外吸收光谱与总有机碳分析联用的技术,有效地区分聚羧酸分子与季铵盐阳离子分子同时存在时各自的吸附行为,并对3种典型结构的季铵盐阳离子与聚羧酸减水剂在水泥-蒙脱土体系吸附行为的相互影响进行了系统研究。结果表明:小分子季铵盐对聚羧酸在水泥表面的吸附无影响,双子型季铵盐掺量达到2.5×10⁴后会促进聚羧酸吸附,聚合物季铵盐则会抑制聚羧酸减水剂在水泥表面的吸附;3种季铵盐在达到一定掺量后,均能有效抑制聚羧酸减水剂在蒙脱土表面的吸附,其中双子型季铵盐和聚合物季铵盐效果更加明显,双子型季铵盐在低掺量下的抑制效果更明显,高掺量下聚合物季铵盐则体现出更优的抑制效果。     

抗泥型聚羧酸减水剂的制备及性能

以甲基丙烯酸（MAA）、甲基丙烯酸羟乙酯（HEMA）为单体,过氧化氢（H₂O₂）/抗坏血酸（Vc）为引发剂,甲基烯丙基磺酸钠（SMAS）为链转移剂,合成了一种抗泥型聚羧酸减水剂,通过红外光谱（FTIR）、凝胶渗透色谱（GPC）对聚合物进行结构表征,通过水泥净浆流动度、蒙脱土层间官能团、X射线衍射和吸附量测试,对其分散性能及抑制蒙脱土机理进行了探究。结果显示：合成的抗泥型聚羧酸减水剂在摩尔比为2.5：1时分散性能最佳,当减水剂折固掺量为0.25%时,水泥初始净浆流动度为268mm;与普通聚羧酸减水剂相比,合成的抗泥型减水剂对蒙脱土敏感性较低,与蒙脱土作用后的层间未出现抗泥型减水剂的特征官能团,层间距为1.40nm,抗泥型减水剂在蒙脱土上的吸附量远小于普通减水剂的吸附量。     

硫酸盐对不同侧链分子量聚羧酸减水剂分散性的影响

通过测定Na2 SO4和CaSO4·2H2O对掺侧链分子量不同的聚羧酸减水剂时水泥净浆流动度及砂浆扩展度的影响来表征硫酸盐对聚羧酸减水剂分散性的影响.结果发现:硫酸盐对聚羧酸减水剂的减水分散性能有不利影响;Na2SO4对聚羧酸减水剂分散性的负面影响较CaSO4·2H2O更显著;此外,侧链分子量较大的聚羧酸减水剂对Na2 SO4更加敏感.     

含三乙醇胺侧基聚羧酸减水剂的制备与性能

将富马酸(FA)与三乙醇胺(TEA)通过酯化反应制备了小分子前驱体小单体4-(2-(二乙醇胺基)乙氧基)-4-氧代-2-丁烯酸(FA-TEA).通过酯化率确定其产率为65％.以丙烯酸(AA)、甲基丙烯磺酸钠(SMAS)、4-(2-(二乙醇胺基)乙氧基)-4-氧代-2-丁烯酸(FA-TEA)、甲基烯丙基聚氧乙烯醚(TPEG)为原料,通过氧化还原体系自由基共聚合反应制备了一种含有三乙醇胺侧链的新型聚羧酸减水剂.通过净浆流动度、凝结时间和自由水率等手段来表征其性能.该减水剂在碱性条件下酯键水解,羧酸根释放,再次吸附,其三乙醇胺侧链形成水化膜具有一定的滑移能力,使分散能力增强.     

梳形结构的侧链密度对聚羧酸系减水剂性能的影响

根据自由基聚合反应原理,通过聚合物分子结构设计和优选合成工艺方法,合成一系列主链聚合度不变、侧链密度不同的梳状结构聚羧酸系减水剂(PCA)。采用凝胶色谱仪测定PCA分子量分布及未反应单体含量。结果发现,对于聚合度为50的聚醚大单体,反应单体的酸醚比在2.5:1以下时,聚合反应转化率较低。为准确反映PCA结构对性能的影响,采用常规添加法、有效聚合物等质量添加法及等摩尔添加法测定不同结构PCA对水泥初始流动度及保持能力的影响,结果表明:随着侧链密度的减小,水泥初始净浆流动度增加;当侧链密度低于25%后,继续减小侧链密度,初始流动度增加不明显;水泥净浆流动性保持能力随侧链密度的减小而显著下降。     

季铵盐对聚羧酸减水剂在水泥-蒙脱土表面吸附的影响EI北大核心CSCD

采用紫外标记技术对聚羧酸分子的紫外吸收进行增强,进而采用紫外吸收光谱与总有机碳分析联用的技术,有效地区分聚羧酸分子与季铵盐阳离子分子同时存在时各自的吸附行为,并对3种典型结构的季铵盐阳离子与聚羧酸减水剂在水泥-蒙脱土体系吸附行为的相互影响进行了系统研究。结果表明:小分子季铵盐对聚羧酸在水泥表面的吸附无影响,双子型季铵盐掺量达到2.5×10^-4后会促进聚羧酸吸附,聚合物季铵盐则会抑制聚羧酸减水剂在水泥表面的吸附;3种季铵盐在达到一定掺量后,均能有效抑制聚羧酸减水剂在蒙脱土表面的吸附,其中双子型季铵盐和聚合物季铵盐效果更加明显,双子型季铵盐在低掺量下的抑制效果更明显,高掺量下聚合物季铵盐则体现出更优的抑制效果。     

阳离子聚合物改善聚羧酸减水剂抗泥性能及作用原理EI北大核心CSCD

以不饱和季铵盐单体与不饱和非(阴)离子单体进行水溶液自由基共聚,合成了系列阳离子聚合物型牺牲剂(CSA)。采用水泥净浆流动度来评价牺牲剂对加蒙脱土水泥中聚羧酸减水剂(PCE)分散性能的影响。结合有机碳吸附、热重分析、X射线衍射等测试手段,不仅考察了聚合单体比例、季铵盐单体种类、非(阴)离子单体种类对牺牲剂作用效果的影响,确定了三甲基烯丙基溴化铵-丙烯酰胺(ATMA-AM2:1)为最佳结构,同时也探明了其作用原理。加入ATMA-AM(2:1)后,有效阻止了PCE分子聚醚侧链进入到蒙脱土层间,显著降低了PCE分子在蒙脱土上的吸附量,增加了其在水泥颗粒上的有效吸附,掺蒙脱土水泥中PCE的流动度由156 mm提升至225 mm,显著改善了蒙脱土对PCE分散性能带来的负面影响。     

Cyclodextrin-modified polycarboxylate superplasticizers as dispersant agents for multiwalled carbon nanotubes

A new type poly(AA-co-β-CD-A-co-TPEG) (PACD) copolymer was prepared by the copolymerization of a novel monovinyl β-cyclodextrin monomer (β-CD-A), acrylic acid, and isoprenyl oxy poly(ethylene glycol) (TPEG-2400). This copolymer could be used as dispersant for multiwalled carbon nanotubes (MWCNTs), which exhibit an excellent dispersion ability. This study mainly investigated the dispersing behavior of the PACD as well as the best ratio between these dispersants and MWCNTs. Transmission electron microscopy was employed to observe the morphology of the dispersed of MWCNTs. ultraviolet–visible–near infrared spectra were utilized to determine the dispersion of MWCNTs and the optimum concentration of PACD. It was found that the polycarboxylate superplasticizer decreased MWCNTs aggregative tendency in water but not as well as PACD. Moreover, the optimum mass ratio of the PACD to the MWCNTs is 5:1. In addition, the effect of PACD on the dispersion ability of MWCNTs was evaluated in cement samples. Our results indicated that MWCNTs could still disperse well with the help of PACD even with the presence of cement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47311.     

不同磷酸酯单体的EPEG型聚羧酸减水剂的制备及抗泥性能

以乙二醇单乙烯基醚（EPEG）为大单体，丙烯酸（AA）为小单体，2-羟乙基甲基丙烯磷酸酯（HEMAP）或封端酰胺磷酸酯（CAP）为功能单体，采用水溶液自由基共聚法合成了两种EPEG型抗泥型聚羧酸减水剂PCE-EP1和PCE-EP2。采用FTIR、1HNMR对减水剂结构进行表征，通过水泥净浆流动度测试了合成的减水剂对水泥的分散性能以及抗泥性能，并结合XRD，XPS探究了减水剂与水泥、蒙脱土之间的作用机理。结果表明：当减水剂折固掺量为0.2%，蒙脱土掺量为2%时，掺PCE-EP1和PCE-EP2有一定的抗泥性。XRD表明说明减水剂PCE-EP1、PCE-EP1对蒙脱土没有进行插层吸附，从而提高了该减水剂对泥土的分散能力。     

Effect of crosslinked polycarboxylate superplasticizers with varied structures on cement dispersion performance

In order to investigate the effect of double bond content in the crosslinkers on the performance of superplasticizers, three different crosslinked polycarboxylate superplasticizers were synthesized herein with various respective crosslinkers. Their impacts on the fluidity, absorption, and hydration behavior of cement systems were studied. The results showed that the polymer, which was synthesized using a crosslinker with four double bonds and five/six double bonds, had higher fluidity and the highest fluidity reached up to 395 mm at W/C of 0.35. Additionally, thermogravimetric analysis and hydration heat tests showed that the crosslinked polycarboxylate superplasticizers could prolong the hydration process of cement slurries. Among these three kinds of crosslinked polycarboxylate superplasticizers, the induction period of cement slurry containing the polymer with crosslinker of four double bonds was significantly extended to facilitate the processing of the concrete. The purpose of this study is to provide strategies for studying high-performance polycarboxylate superplasticizers with novel topological structure.     

聚羧酸减水剂在水泥颗粒表面的吸附行为

合成一系列聚羧酸减水剂,探讨不同单体摩尔比对其吸附性能的影响。结果表明,当n(烯丙醇聚氧乙烯醚)∶n(2-丙烯酰胺-2-甲基丙磺酸钠)∶n(丙烯酸)∶n(马来酸酐)=1∶0.14∶3.6∶2.6时,产物吸附性能最优。并利用总有机碳分析技术,研究了不同温度、不同浓度下最优产物在水泥颗粒表面的吸附动力学和热力学。动力学研究结果表明：聚羧酸在水泥颗粒表面的吸附过程符合Lagergren吸附速率方程,吸附速率常数k=0.01594 min-1(30℃),表观活化能Ea=17.9647 kJ·mol-1。热力学研究结果表明：随温度升高,聚羧酸在水泥颗粒表面的吸附量增大;求得吸附热力学参数分别为ΔHad=-24.788 kJ·mol-1,ΔSad=0.050 kJ·mol-1·K-1,ΔGad=-39.886 kJ·mol-1(30℃),可知该吸附过程是自发的放热反应。理论上温度升高对吸附不利,但因放出的热量促进水泥水化,导致聚羧酸分子容易掺杂到水化产物中,从而使更多聚羧酸吸附到水泥颗粒表面,令其吸附量反而增大。     

纳米SiO2对聚羧酸减水剂的吸附作用研究

采用红外光谱、紫外-可见分光光度计研究了纳米SiO2对聚羧酸减水剂的吸附作用,并利用纳米粒度zeta电位仪、旋转粘度计研究了纳米SiO2吸附减水剂后对其分散性以及新拌水泥浆体流动性的影响.研究结果表明,纳米SiO2对聚羧酸减水剂存在吸附作用,吸附量随减水剂浓度的增大而增加,当减水剂浓度增加到5g/L时,吸附量趋近饱和.纳米SiO2对聚羧酸减水剂的吸附作用,使其团聚粒径增大,粒径分布曲线整体向大颗粒方向偏移,分散性大大降低.将纳米SiO2溶于拌和水中,先加入水泥搅拌,然后再加入减水剂搅拌,可减小纳米SiO2对减水剂的吸附,增大减水剂的利用效率,提高水泥浆体的流动性.     

Effect of chain transfer agents in polycarboxylate superplasticizer on slump-retention of concrete

Two types of slump-retention polycarboxylate superplasticizers (PC-M and PC-S) were synthesized by using 3-mercaptopropionic acid or sodium hypophosphite as chain transfer agents, the effects of polycarboxylate superplasticizers on slump-retention of cement and concrete were investigated, and the mechanism of action and the structure of polycarboxylate superplasticizers were investigated by using conductivity, complexing Ca²⁺ concentration, gel permeation chromatography (GPC), nuclear magnetic resonance hydrogen spectroscopy (¹H-NMR), and nuclear magnetic resonance phosphorus spectroscopy (³¹P-NMR). The results indicated that the slump flow of cement paste mixed with PC-M was increased quickly within 60 min and then lost gradually, while PC-S increased slowly and evenly within 240 min. The slump flow of concrete mixed with PC-S reached 405 mm after 150 min, but the concrete mixed with PC-M was almost no fluidity after 150 min. The conductivity of the PC-M aqueous solution decreased quickly within 45 min, then slowly decreased, while the conductivity of the PC-S aqueous solution decreased slowly within 180 min. PC-M had a much greater complexation ability of Ca²⁺ than PC-S. The composition and structure of the two slump-retention polycarboxylate superplasticizers were altered by different chain transfer agents, and the hydrolysis-adsorption capacity of each component was different. The rate of hydrolyzation-adsorption of each component was PC-M₃ ≈ PC-S₃>PC-M₁>PC-M₂ ≈ PC-S₁>PC-S₂. The faster the adsorption rate, the faster the slump flow loss of concrete.     

β-环糊精/聚醚共聚乙酰胺填充膜的制备及渗透汽化分离水中微量苯酚

将β-环糊精（β-CD）添加到聚醚共聚乙酰胺（PEBA）中制备β-环糊精/聚醚共聚乙酰胺填充膜（β-CD-f-PEBA）,用于苯酚-水的渗透汽化分离研究。SEM、FTIR表明β-环糊精在膜中分散均匀且与膜结合紧密,与膜间只有氢键相互作用而未发生化学交联。拉伸实验表明膜的拉伸强度和断裂强度均随着β-CD添加量的增加先减小后增大。采用基团贡献法计算了PEBA、苯酚及水的溶解度参数,证明PEBA膜对苯酚具有较高的选择吸附性。通过溶胀验证膜对苯酚的选择吸附性能,膜对苯酚的吸附量度随着料液中苯酚浓度和膜中β-CD添加量的增加而增加。考察了PEBA和β-CD-f-PEBA膜的渗透汽化性能,当β-CD填充量为0.5%（质量）时,分离效果最佳,渗透通量和分离因子分别为3062.9 g·m^-2·h^-1和43.3。通过Arrhenius方程计算苯酚和水的渗透活化能分别为97.19和52.12 kJ·mol^-1。重复实验表明β-CD-f-PEBA膜的操作稳定性良好。     

β-Cyclodextrin functionalized graphene oxide: an efficient and recyclable adsorbent for the removal of dye pollutants

A novel method for the preparation of β-cyclodextrin grafted graphene oxide (GO-β-CD) has been developed. The GO-β-CD was characterized by Fourier transform infrared spectroscopy, ¹³C NMR spectroscopy, Raman spectroscopy and thermogravimetric analysis. The ability of GO-β-CD to remove fuchsin acid from solution was also studied. The GO-β-CD had an excellent adsorption capacity for fuchsin acid and could be recycled and reused. The adsorption capacities of GO-β-CD for other dye pollutants such as methyl orange and methylene blue were also investigated. The absorption capacities for the three dyes are in the order: fuchsin acid>methylene blue>methyl orange.     

Research on the performances of VPEG macromonomer grafted different functional groups to prepare polycarboxylate superplasticizers

The advent of novel polyether macromonomer has garnered significant attention within the industrial domain. In this study, a range of polycarboxylate superplasticizers (PCEs) was produced via free radical polymerization, employing a new polyether monomer, 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG). This monomer served as the predominant component and was grafted with various functional monomers on its main chain. The molecular configuration of the resultant PCEs was discerned through Fourier infrared spectroscopy and gel permeation chromatography, while the surface tension underwent assessment via a surface tension meter. Both the initial and subsequent fluidity of cement paste and mortar were leveraged to ascertain the dispersion and retention efficacy of the synthetic PCEs. The ramifications of diverse functional group grafts of the new polyether monomer on the cement hydration procedure and strength attributes were elucidated via setting time, hydration heat assays of cement paste, SEM analysis, and compressive strength evaluations of mortar. Observations reveal that the carboxylic acid group significantly reduces surface tension, whereas the sulfonic acid group's effect remains minimal. The incorporation of both the amide and sulfonic acid groups marginally impacts the preliminary dispersion efficacy of PCEs but notably affects dispersion retention. Furthermore, these functional groups facilitate cement hydration, expedite the primary setting time of the cement paste, and bolster the initial compressive strength of the mortar. Specifically, the grafted of sodium methacrylsulfonate (SMAS) yields the most noticeable results. Finally, the working mechanism of PCEs with varying molecular structures has been explained in light both theoretical and experimental results. This research offers valuable insights for subsequent investigations into the fabrication of polycarboxylate superplasticizers using the VPEG macromonomer.     

聚羧酸盐侧链长度对水煤浆分散性能的影响及其作用机理

合成了一系列具有不同侧链长度的梳型聚羧酸盐(PC),研究了PC侧链长度对水煤浆的分散和流变性能的影响,使用X射线光电子能谱(XPS)分析了PC在煤水界面的吸附,并结合水煤浆Zeta电位及PC对煤颗粒的润湿性探讨了PC的分散作用机理,为设计制得高效的聚羧酸盐水煤浆分散剂提供依据。结果表明:长主链、短侧链和高阴离子基团含量的PC500(侧链聚合度)具有优良的分散性,所制水煤浆属假塑性流体。PC在煤表面呈单分子层吸附,其中PC500的吸附密度和吸附厚度均最大,分别为0.638 mg·m^-2和4.20 nm,其对煤粒润湿性也较好,所制水煤浆Zeta电位绝对值最高。侧链长度适中的PC500通过平衡吸附层厚度与Zeta电位发挥空间位阻和静电斥力作用分散水煤浆,其可有效地降低水煤浆Gibbs能,使煤粒间“团聚”减弱,浆体分散性提高。