聚羧酸类减水剂的分子设计与结构性能关系

根据高性能减水剂分子设计原理,通过甲基丙烯酸、甲基丙烯磺酸钠、甲氧基聚乙二醇丙烯酸酯等单体的自由基溶液聚合制备了分子链中含有聚氧乙烯链和阴离子基团的聚羧酸类减水剂。结果表明,接枝链的密度和侧链的长度影响减水剂的性能,通过选择适宜长度的侧链及调节共聚单体的比例和聚合物分子量可以增大减水剂的分散性和分散保持性。另外还通过红外光谱对产物进行了表征和分析,结果表明已得到预期结构的聚羧酸类减水剂。     

β-环糊精侧链对聚羧酸减水剂抑制蒙脱土的影响

采用水泥净浆和混凝土试验，详细研究了β-环糊精侧链对聚羧酸减水剂抑制蒙脱土负效应的影响。试验表明，与仅含有聚氧乙烯侧链的传统聚羧酸减水剂相比，蒙脱土对掺加含有β-环糊精侧链的聚羧酸减水剂水泥净浆流动度的负作用影响明显减弱；蒙脱土（1.0%，以砂质量计）存在时，为获得与无蒙脱土时相同的混凝土坍落度，β-环糊精类聚羧酸减水剂的掺量增幅减小，掺加β-环糊精类聚羧酸减水剂的混凝土抗压强度下降幅度减小。结合吸附试验分析，β-环糊精类聚羧酸减水剂抑制蒙脱土负效应能力的增强应归功于其侧链中的β-环糊精基团，β-环糊精基团具有中空筒状的刚性结构，其显著的空间位阻效应将阻止蒙脱土颗粒继续吸附其他β-环糊精类聚羧酸分子，进而提高聚羧酸减水剂抑制蒙脱土负效应的能力。     

不同结构聚羧酸减水剂在吸附质浆体表面的吸附-分散效应

为考察不同侧链密度的减水剂分子在水泥-钠基膨润土浆体中的吸附-分散效应,以丙烯酸和2-甲基丙-2-烯基聚乙二醇醚自由基共聚法,通过调整链转移剂构建出适当主链长度且不同侧链密度的聚羧酸减水剂.采用GPC、Zeta电位、TOC、流动度测试技术表征,着重考察了相近主链长度、不同侧链密度的减水剂在水泥-钠基膨润土混合浆体中的吸附-分散特性.结果 表明:侧链密度设计越高,主链长度同步减小,减水剂分子初始吸附量越小;内掺钠基膨润土后在分散性能方面侧链密度高的占优势,且内掺量越大,侧链密度高的减水剂抗泥质吸附能力越强.     

聚羧酸系减水剂的构效关系及作用机理研究进展

简要回顾了减水剂的发展历程,从减水剂中侧链长短、阴离子电荷密度、羧基连接方式、主链聚合度等因素阐述了聚羧酸系高效减水剂的结构与性能关系,综述了其作用机理,提出了聚羧酸系减水剂今后的研究方向.     

梳形共聚物分散剂侧链长度对水泥浆体分散性能的影响及机理

合成了系列具有不同侧链长度的梳形共聚物,并研究了共聚物侧链长度在不同水灰比条件下对水泥浆体分散、流变和ζ电位的影响规律,同时结合吸附性能,对添加梳形共聚物的水泥浆体粒子间作用能进行了计算.结果表明:含有较高吸附基团的短侧链梳形共聚物具有静电捧斥和空间位阻两种效应,其分散性能受水灰比影响较大;相反地以空间位阻效应为主的长侧链聚醚梳形共聚物则对水灰比体现出了良好的适应性.同短侧链梳形共聚物相比,长侧链聚合物由于具有较大的第二最小值(Vmin)和较长的平衡距离更适合于在浓悬浮体系中用作高性能分散剂.     

马来酸类聚羧酸减水剂的合成及其对水泥净浆流动性的影响研究

以马来酸酐、聚乙二醇、丙烯酸等为原料,采用先酯化再共聚的方法,合成了一系列侧链结构不同的聚羧酸减水剂,研究了反应温度、单体摩尔比对酯化率的影响,以及聚氧乙烯侧链类型、侧链含量对水泥净浆流动性的影响。通过1HNMR表征了酯化物和共聚物的结构,采用酸碱滴定法测定其酯化率。     

MA-IMPEG-AMPS三元共聚减水剂的合成及性能

用自制酯化大单体甲氧基聚乙二醇衣康酸单酯,与马来酸酐、2-丙酰胺-2甲基丙磺酸在水溶液中共聚反应合成了含有羧基、酯基和聚氧乙烯基侧链的新型聚羧酸盐减水剂。结果表明,该新型减水剂因多引入了一个羧基,增大了羧基密度,减水率和保塌性均得到了提高。在掺量为1%,初始水泥净浆流动度为280 mm,初始塌落度达到220 mm,混凝土的抗压强度得到提高。     

含受阻酚侧链的聚氨酯阻尼性能研究

将二缩三乙二醇双〔β-(3-叔丁基-4-羟基-5-甲基苯基)丙酸酯〕(抗氧剂245)羧基化,得到具有一定反应活性的受阻酚基团,通过与多苯基多甲基多异氰酸酯(20S)的反应,合成带受阻酚侧链的多异氰酸酯,制备受阻酚型聚氨酯阻尼材料;讨论了羧基受阻酚及其含量、作为阻尼填料的抗氧剂245以及nNCO/nOH对聚氨酯材料阻尼性能的影响。结果表明,引入羧基受阻酚基团,聚氨酯材料的阻尼性能有很大的提高,并随引入的羧基受阻酚含量的增加而提高;当羧基受阻酚占20S质量分数为21.9%时,提高阻尼填料抗氧剂245的含量、减小nNCO/nOH,聚氨酯材料的阻尼性能增加。     

聚氧乙烯苯胺醚扩链剂合成研究

讨论了聚氨酯用扩链聚氧乙烯苯胺醚的合成工艺及某些因素对产品性能的影响。     

聚醚侧链聚羧酸类减水剂的结构及应用性能

通过大分子反应,合成了一类主链带羧基、磺酸基,支链带聚氧乙烯基醚的聚羧酸系高效减水剂。利用IR和1H NMR表征了其结构,并通过对减水剂溶液表面张力、水泥颗粒表面吸附量以及溶液的电导率的测定,发现研制的减水剂能降低水的表面张力,并被吸附在水泥颗粒表面从而降低了水泥颗粒的表面能,使得水泥净浆有较好的分散作用,实验表明本研究制备的聚羧酸系减水剂对水泥颗粒有较好的分散作用。     

不同酯类单体对缓释型聚羧酸减水剂分散性能及分散保持性能的影响

为探究不同酯类单体对缓释型聚羧酸减水剂分散性能及分散保持性能的影响规律和作用机理,采用不同分子结构酯类单体作为改性原料制备不同缓释型聚羧酸减水剂,并通过水泥浆体经时流动度、Zeta电位、总有机碳、电导率、傅里叶红外光谱、核磁共振氢谱等测试分析其宏观分散性能及分散保持性能与微观结构的变化规律及作用机理。结果表明:采用单酯类单体(丙烯酸羟乙酯、丙烯酸羟丙酯、丙烯酸甲酯)和双酯类单体(马来酸二甲酯)作为功能单体改性的缓释型聚羧酸减水剂分散保持性能较为优异,4 h时流动度相比初始流动度仍有所提升,同时相比未改性空白组,4 h 时流动度显著提升,后期分散性能更为优异。主要机理为:碱性环境下酯基在水泥浆体中缓慢水解出锚固基团羧基阴离子,发挥分散作用;不同分子结构的酯类单体位阻效应和基团电负性存在差异,导致水解速率和水解程度不同,从而使各种缓释型聚羧酸减水剂分散性能及分散保持性能存在差异。     

聚羧酸系混凝土减水剂的研究进展及发展趋势

详细介绍了聚羧酸系混凝土减水剂的分子结构、作用机理、制备方法及其性能的影响因素.简要概述了国内外聚羧酸系混凝上减水荆的研究进展,并提出了今后聚羧酸系混凝土减水剂的发展方向.     

端羟基双子季铵盐对聚羧酸盐减水剂抗泥性能的影响

以1,4-对二氯苄为连接基团，分别以三乙胺和N,N-二甲基乙醇胺为头基，合成了具有不同端基的双子季铵盐（分别标记为KNJ-1和KNJ-2）。将其作为抗泥剂与聚羧酸盐减水剂复配以改善粘土对减水剂的负面效应，探究端羟基的引入对抗泥效果的影响。通过FT-IR和1H NMR对其进行结构表征。净浆流动实验考察抗泥剂的对流动度的影响，并结合XRD、XPS和 Zeta电位分析其与蒙脱土的作用机理。实验结果表明：与KNJ-1相比，加入0.3‰KNJ-2使水泥净浆初始流动度提高了35mm, 2h后流动度提高了165mm,表现出更好的抗泥效果。XRD和 XPS结果表明KNJ-2在蒙脱土的表面和层间吸附均优于KNJ-1，Zeta电位结果显示KNJ-2的加入使表面电位从初始的-15.67mV上升到-0.15mV。表明羟基可通过氢键作用优先吸附在蒙脱土的表面和层间，占据大量活性位点，减少了对聚羧酸盐减水剂的吸附，保障减水剂的高效分散能力，从而达到对粘土抑制的效果。     

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.     

Effects of connection mode between carboxyl groups and main chains on polycarboxylate superplasticizer properties

Preparation and characterization of polycarboxylate superplasticizers of IPCs ( copolymer of itaconic acid and allyl polyoxyethylene ether) and MPCs (copolymer of maleic anhydride and allyl polyoxyethylene ether) are shown. The difference between IPCs and MPCs is that half of the carboxyl groups of IPCs indirectly connect to the main chains through methylene. The effects of the carboxyl group‐main chain connection mode on the properties of IPCs and MPCs were investigated by assessing the paste fluidity and the pore diameters and compressive strength. The interaction between IPCs (MPCs) and cement were revealed by zeta‐potential and the adsorption amount. The results indicated that the indirect connection mode favorably improved paste fluidity, decreased pore diameters, and increased the compressive strength compared with the direct connection mode. This is likely because that when carboxyl groups are connected to the main chains indirectly, more moving space allows easier adsorption on cement particles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

蒸养条件下两性聚羧酸减水剂对胶砂及混凝土强度的影响

合成了阴离子型和两性型聚羧酸减水剂,研究了两类聚羧酸减水剂对水泥水化热、蒸养胶砂和蒸养混凝土强度的影响.结果表明:在蒸养条件下,与阴离子型聚羧酸减水剂相比,掺两性型聚羧酸减水剂的水泥水化温峰更高;在相同水灰比时,掺两性聚羧酸减水剂的蒸养胶砂和蒸养混凝土的强度也更高.XRD分析可知,掺入两性聚羧酸减水剂在蒸养条件下生成更多的AFm和氢氧化钙,促进了C3S和C2S的水化.     

Effects of crosslinked polycarboxylate superplasticizers with crosslinking agent containing ester and amide groups on the properties of cementitious systems

Herein, crosslinked polycarboxylate superplasticizers were synthesized using acrylic acid, sodium methylallyl sulfonate and methyl polyethylene glycol acrylate as monomers, and monomers that contain either ester or amide groups as crosslinking agents. The superplasticizers that were synthesized from the ester- and amide-based crosslinking agents were respectively denoted as SP-E and SP-N. In addition, a series of performance characterizations were carried out to explore the influence of different functional groups in crosslinking agents on the performance of superplasticizers. Fluidity test results showed that the dispersibility and fluidity retention of cement pastes treated with the SP-E were better than those of cement pastes treated with SP-N. Meanwhile, the viscosity of the sample containing SP-E was lower than that containing SP-N. In addition, the amount of the two superplasticizers that had become adsorbed onto the surfaces of cement particles also differed, and in this case the adsorption capacity of SP-E was greater than that of SP-N. X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy tests showed that the ester-group based SP-E superplasticizers promoted cement hydration to a greater degree than that was achieved with their amide-bearing SP-N counterparts. This study would provide valuable insight for the development of crosslinked polycarboxylate superplasticizers.     

聚醚型聚羧酸减水剂的合成和表征及对水泥的微观作用机制

本文以聚醚、丙烯酸、丙烯酸羟乙酯为原料,通过自由基聚合法合成了聚羧酸减水剂JS-PCE和BT-PCE。通过正交优化所得的JS-PCE合成条件为:聚合温度25 ℃,抗坏血酸-巯基丙酸混液、丙烯酸滴加时间分别为3 h、2.5 h,酸醚物质的量比为4.25∶1,引发剂加量为聚醚质量的1.10%。添加JS-PCE的水泥净浆流动度达230 mm,表现出较好的流动性。采用界面化学及电化学等方法探究了减水剂对水泥的微观作用机制,结果表明聚羧酸减水剂在水泥颗粒表面存在饱和吸附量,其与水泥颗粒存在强吸附作用,因此产生分散和减水作用。流变行为分析得出JS-PCE和BT-PCE的最佳折固掺量分别为0.3%、0.4%。     

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.