Synthesis of a Macromer, MPEGAA, Used to Prepare an AMPS-modified Polyacrylic Acid Superplasticizer

A macromer, methoxypolyethylene glycol acrylate （MPEGAA）, was synthesized by direct esterification using methoxypolyethylene glycol （MPEG-1200） and acrylic acid （AA） as the main materials. MPEGAA was then used to prepare a polyacrylic acid superplasticizer modified with 2-acrylamido-2- methylpropane sulfonic acid （AMPS）. A single-factor test was performed to investigate the effects of the molar ratio of acid to alcohol （n（AA）/n（MPEG））, inhibitor amount, catalyst amount, temperature, and time of esterification on the synthesis of MPEGAA. The experimental results showed that the optimal esterification conditions were as follows： n（AA）/n（MPEG）, 3.5：1; amount of hydroquinone （as an inhibitor）, 1.2%; amount of para-toluenesulfonic acid （as a catalyst）, 5.5%; reaction temperature, 95 ~C; and reaction time, 6 h. The AMPS- modified polyacrylic acid superplasticizer prepared under the optimal esterification conditions enabled the achievement and maintenance of high cement dispersibility. At an admixture amount of 0.15%, the cement paste fluidity was initially as high as 300 mm, and then decreased to 315 mm after 1 h and to 290 mm after 2 h.

Synthesis and Properties of an AMPS-Modified Polyacrylic Acid Superplasticizer

A 2-acrylamide-2-methyl propylene sodium sulfonic （AMPS）-modified polyacrylic acid superplasticizer was synthesized using aqueous solution polymerization with the major monomers including the self-made active macromers polyethylene glycol mono-methyl ether acrylate acrylic （MPEGAA）, acrylic acid （AA）, AMPS, and sodium methyl allyl sulfonate （SMAS）. The ratios of the monomers were determined using an orthogonal experiment. This research focused on the effects of the dosages of different macromers, the polymerization conditions, and the length of MPEGAA side chains on the properties of the AMPS-modified polyacrylic acid super-plasticizer. The best polymerization conditions of the AMPS-modified polyacrylic acid superplasticizer are when （n（MPEGAA）：n（SMAS）：n（AMPS）：n（AA） equals 0.1：0.1：0.2：0.65, the molecular weight of monomethoxypolyethylene glycol is 1 200, the initiator ammonium persulfate accounts for 5% of the total mass of the polymerized monomers, the polymerization temperature is 80 ~C, and the reaction time is 4 h. The AMPS-modified polyacrylic acid superplasticizer synthesized in the best conditions exhibited excellent dispersivity and dispersion retainability. When the dosage ratio was 0.24%, the initial fluidity was 400 mm and the fluidity had nearly no loss after 1 h.

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.

Porous polymer microsphere functionalized with benzimidazolium based ionic liquids as effective solid catalysts for esterification

To prepare polymer supported ionic liquids(PSILs)as effective catalysts for esterification,the free radical suspension copolymerization of vinylbenzyl chloride(VBC,monomer),styrene(St,monomer)and divinylbenzene(DVB,crosslinker)with the addition of n-heptane(porogen)was carried out for the fabrication of the porous polymer(PVD)microsphere as support,followed by the immobilization of sulfonic acid-functionalized ionic liquids by the successive treatment of benzimidazole(BIm),1,3-propane sultone and sulfuric acid(H2SO4)or trifluoromethanesulfonic acid(CF3SO3H).The effects of the compositions of DVB and n-heptane on the internal structure of the polymer supports were investigated,and it was found that the support with 40 wt%DVB and 60 wt%n-heptane(with relative to the monomer)could endow the final PSILs with the relatively optimal catalytic performance.The preliminary experiment in the batch reactor indicated that PSILs herein exhibited higher catalytic activities than commercial Amberlyst 46 resin for the esterification of propanoic acid(PROAc)with n-propanol(PROOH).Consequently,the optimal PSILs catalyst,PVD-[Bim-SO3H]HSO4,was selected for further study in the batch reactive distillation column because of low cost and its ease of preparation.The yield of propyl ropionate(PROPRO)could reach up to 97.78%at the optimized conditions of PROOH/PROAc molar ratio(2:1)and catalyst dosage(2.0 wt%).The investigation of the reaction kinetic manifested that the calculated results of second order pseudo-homogeneous kinetic model were in good agreement with experimental values.The pre-exponential factor and activation energy were 4.12×107 L·mol-1·min-1 and 60.57 k J·mol-1,respectively.It is worth noting that the PSILs catalyst could be simply recovered and reused with relatively satisfactory decrease in the catalytic activity,which made it an environmental friendly and promising catalyst in the industrial application.

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%.

柠檬酸改性低分子量减水剂的合成、性能及机理

以柠檬酸(CA)和聚乙二醇聚丙二醇单甲醚(MPEPPG)为主要反应原料,通过酯化反应合成一种柠檬酸改性低分子量减水剂(LMWS)。通过红外光谱、核磁氢谱和凝胶色谱测试获得合成减水剂的结构参数信息。同时通过动态光散射(DLS)、水泥净浆Zeta电位、减水剂对水泥的吸附性能、水泥净浆凝结时间、水泥水化热、水泥净浆塑性粘度、水泥净浆流动度及混凝土性能等研究对比了相同酸醚比(n(CA)∶n(MPEPPG)=1∶1)时不同分子量LMWS的综合性能。结果表明:相同掺量条件下,分子量适中的LMWS-3显著降低水泥净浆的塑性粘度并延缓水泥的水化进程,具有优异的初始分散和分散保持性能。

醚酯共聚法制备减水保坍型聚羧酸减水剂及其性能研究

以丙烯酸羟乙酯(HEA)、异戊烯基聚氧乙烯醚(TPEG)、丙烯酸(AA)为主要原料,引入丙烯酸一缩二乙二醇酯(EGD),在45℃的氧化-还原体系下合成减水保坍型聚羧酸减水剂。结果表明,相对市售聚羧酸减水母液,该产品有更好的分散性和保坍能力,且自带引气效果,能有效改善混凝土和易性,提高混凝土抗压强度,综合性能更优。

马来酸酐在聚羧酸盐减水剂合成中的应用

随着聚羧酸盐减水剂的不断发展,马来酸酐在其合成中的应用也越来越多。根据马来酸酐与丙烯酸(以及甲基丙烯酸)各自的特性和聚羧酸盐减水剂合成的技术要求,分析了它们在合成过程中的作用和主要差别,并概述了马来酸酐在合成中的应用情况,最后提出了马来酸酐在合成中应用的几点建议。马来酸酐及其酯的分子结构和化学活性独特,应用于聚羧酸盐减水剂的合成必将有广阔的前景。

机械活化对玉米淀粉结晶结构与化学反应活性的影响

采用搅拌球磨机对玉米淀粉进行机械活化,用X射线衍射仪、差示扫描量热仪、扫描电子显微镜及粒度分析仪等考察了机械活化对玉米淀粉结晶结构、热特性、颗粒形貌及粒度变化的影响。并将不同活化时间的玉米淀粉在相同条件下与乙酸酐进行酯化反应及与丙烯酰胺进行接枝共聚反应,通过研究机械活化对酯化反应取代度、接枝共聚反应接枝率与接枝效率的影响规律来探讨机械活化对玉米淀粉化学反应活性的影响。结果表明,机械活化预处理能显著提高玉米淀粉酯化反应的取代度及接枝共聚反应的接枝率与接枝效率,说明机械活化能有效地提高玉米淀粉的化学反应活性。其原因是玉米淀粉在机械活化过程中其结晶结构与颗粒形貌均受到破坏,结晶度降低,最终由多晶态转变成非晶态。并随活化时间的延长,糊化温度及糊黏度下降,流动性增强,从而使反应试剂的扩散阻力下降,易于扩散到淀粉分子中参与反应。

共聚型马来酸酐系减水剂的制备与结构性能的研究

研究了共聚型马酸酐系减水剂的制备与性能。以马来酸酐和聚乙二醇(PEG)为原料,经酯化制得酯化物单体;并测定其酯化率,用IR表征了酯化物的结构。以马来酸聚乙二醇单酯、2-丙烯酰胺-2-甲基丙磺酸(AMPS)和甲基丙烯酸为原料通过共聚反应制得减水剂,讨论了共聚反应中影响减水剂净浆流动度的因素,并用GPC表征了共聚物减水剂的分子量及分布。将减水剂添加到水泥浆中制得水泥石样品,通过SEM分析了水泥的早期微观结构。结果表明,当n(酯化物)∶n(MAA)∶n(AMPS)=1∶3∶1.5时所得减水剂净浆流动度为265mm,GPC分析表明减水剂平均分子量Mn=12562,分散系数Mw/Mn=2.1361,SEM分析表明减水剂使水泥石大孔减少,生成了更多较小的孔,结晶生长更密实。

复合变性对淀粉性质的影响研究

复合变性淀粉是近年来研制开发的一类新型变性淀粉,是将淀粉采用两种或两种以上的变性方法而获得的淀粉衍生物。与单一变性淀粉相比,表现出更优越的物理化学性能,从而将会大大拓宽变性淀粉的工业应用领域。本文概述了几种典型的复合变性淀粉,如氧化淀粉、酯化淀粉、醚化淀粉及接枝共聚型复合变性淀粉的国内外研究现状,并展望了该类变性淀粉的研究方向及其潜在的发展前景。

新型聚羧酸系高效减水剂的合成及性能研究

结合高分子科学及混凝土科学的“分子设计”原理,将丁氧基聚氧乙烯甲基丙烯酸酯(BPEOMA)、AA、MAA、不饱和磺酸盐单体通过自由基水溶液共聚合的方法合成了一种新型梳状聚羧酸系高效减水剂SP,通过傅立叶变换红外光谱表征了减水剂的分子结构。重点研究了磺酸盐种类、用量,不饱和羧酸及引发剂对减水剂性能的影响。结果表明,减水剂SP具有良好的分散性及分散保持性能,折固掺量为0.3%,水灰比为0.29时,水泥净浆流动度可达290mm,90min内坍落度基本不变,且无泌水现象。

改性木质素磺酸钙高效减水剂的制备和应用

用H2O2先对木质素磺酸钙进行氧化,然后将木质素碳酸钙氧化产物在过硫酸铵引发下与丙烯酰胺共聚,合成了一种改性木质素磺酸钙高效减水剂(AMCL)。通过红外光谱表征了氧化和共聚反应,并对AMCL进行了水泥净浆性能测试。结果表明,AMCL的分散性、缓凝性和引气性较木质素磺酸钙有明显改善,水化产物结构更加密实;在AMCL掺量为水泥质量的0.5%、水灰比为0.35时,水泥净浆流动度达245 mm;标准稠度下,AMCL掺量为0.5%时,水泥净浆减水率达到15.7%,3 d、7 d和28 d硬化水泥浆体的抗压强度比分别为119.7%、126.7%和121.0%,抗折强度比分别为109.5%、126.7%和123.4%。

水溶性苯乙烯改性醇酸树脂的合成工艺研究

采用脂肪酸法合成基础醇酸树脂,然后用苯乙烯和丙烯酸接枝共聚,制得了水溶性苯乙烯改性醇酸树脂。通过探讨油度、K值、苯乙烯、丙烯酸用量等因素对改性后树脂成膜性能的影响,确定了水溶性苯乙烯改性醇酸树脂的最佳工艺和配方;同时比较了水溶性常规未改性醇酸清漆、溶剂型苯乙烯改性醇酸清漆与水溶性苯乙烯改性醇酸清漆的性能优劣。结果表明:水溶性苯乙烯改性醇酸树脂较未改性醇酸树脂干性、硬度有了较大提高,与溶剂型苯乙烯改性醇酸树脂相当;当选取油度60%、K值1.05、苯乙烯质量分数35%、丙烯酸质量分数6.5%时,水溶性苯乙烯改性醇酸树脂自干表干达到0.5 h,实干20 h,硬度HB,水溶性优异,漆膜耐水、耐碱性获得很大提高,同时兼具了性能要求和环保要求。

马来酸酐类聚羧酸盐减水剂的合成与性能研究

目前聚羧酸减水剂大多由甲基丙烯酸合成,而马来酸酐因其结构对称、活性较低等特点而合成工艺简单、易于控制。本文研究以马来酸酐、甲氧基聚乙二醇、乙烯基磺酸钠、甲基丙烯酸为原料采用先酯化再共聚的方法合成出了含有羧酸基、磺酸基、聚氧乙烯基的马来酸酐类聚羧酸减水剂。酯化反应是极其关键的一步,通过研究表明马来酸酐甲氧基聚乙二醇单酯最佳合成条件为:酸醇比为1.15:1、催化剂用量为MPEG质量的6%,、反应时间4h,反应温度为110℃;马来酸酐聚羧酸减水剂的最佳合成配比为n(MPEG-MA):n(SVS):n(MAA)=1:0.75:5。马来酸酐聚羧酸减水剂最佳掺量为0.5%,与市场上的减水剂最佳掺量时的效果相当。

马来酸酐类聚羧酸减水剂研究现状及展望

由于马来酸酐及其酯的特殊性质,通过介绍聚羧酸减水剂合成过程中马来酸酐的参与形式及特点,并详细分析马来酸酐与聚乙二醇和甲氧基聚乙二醇的酯化特点及运用,并对马来酸酐在今后合成与运用提出几点建议。

聚羧酸系减水剂的合成研究

采用水溶液聚合法,将自制的酯化大单体聚乙二醇单甲醚甲基丙烯酸酯(MPEGMA)与甲基丙烯酸(MAA)、甲基丙烯酰基磺酸钠(SMAS)共聚合成聚羧酸系减水剂,探讨了反应浓度、加料方式、MAA与MPEGMA的摩尔比、SMAS与MPEGMA的摩尔比、引发剂用量(相对于所有单体质量和的百分比)、聚合温度和反应时间对所合成聚羧酸系减水剂性能的影响.结果表明:采用最佳工艺参数制备的聚羧酸系减水剂在掺量仅为0.15%(质量分数)时就具有良好的分散性和保塑性.

梳形支化结构聚羧酸高性能减水剂的合成

以支化活性大单体与丙烯酸进行水溶液自由基共聚,合成了梳形支化结构聚羧酸高性能减水剂。考察了引发体系、单体投料比及滴加时间、链转移剂种类及用量、聚合浓度等合成条件对减水剂分散性能的影响。确定了最佳合成条件为:采用L-抗坏血酸与双氧水的氧化还原引发体系,L-抗坏血酸的用量为1%;丙烯酸(AA)与大单体的投料摩尔比为4∶1,AA的滴加时间为3 h;链转移剂用量为单体总摩尔数的2.0%;聚合浓度为50%。通过凝胶渗透色谱测得合成减水剂的重均分子质量为47 500,DAM大单体的转化率为89.6%。与常规结构聚羧酸减水剂相比,所制备的梳形支化结构聚羧酸减水剂具有较高的减水率和较好的坍落度保持能力。

共聚改性阻燃PET的制备

采用酯化前和酯化后加入阻燃剂2-羟乙基苯基次磷酸(CEPPA)2种方法制备阻燃聚对苯二甲酸乙二醇酯(PET),研究了阻燃PET的结构与性能。结果表明:酯化前后加入CEPPA所得的阻燃PET分子结构相同,CEPPA参与了PET的聚合反应,以化学链连接到PET大分子链上。2种方法制备的阻燃PET的热性能和阻燃性能相差不大。酯化前加入CEPPA对阻燃PET的热转变温度改变较小,有利于阻燃PET切片的纺丝及后加工,酯化后加入CEPPA更合适大规模阻燃PET的生产。