【作者】 李明；

【导师】 朱岩；

【作者基本信息】 武汉理工大学 ， 化学工程与技术， 2018， 硕士

【摘要】 PCE由于分子结构设计性强、掺量低、工艺简单等优点,在工程领域的应用越来越广泛。随着国内PCE合成技术的发展,在实际工程应用中也出现了一些亟待解决的问题。因此,梳理PCE合成工艺条件、分子结构与应用性能关系成为研究的热点和难点。本文采用低温氧化还原引发体系,以IPEG-2400、AA和MA为主要原料合成醚型PCE,并通过FT-IR、~1H NMR、GPC、UV和DSC进行分子结构表征,着重研究了大小单体比例、引发剂和MA用量对PCE结构参数的影响规律及结构参数(PEO支链密度、-COO~-密度、主链长度)对其吸附分散性能影响规律。研究结果表明:(1)在AA-IPEG共聚物的合成工艺中,控制其他工艺参数不变的条件下,随着AA用量的增加,IPEG的转化率不断提高;随着改性单体MA用量的增加,PCE主链上-COO~-的数量越来越多;随着引发剂用量的增加,PCE主链长度越来越短且相对分子量分布越来越窄。(2)在相同PCE掺量条件下,PCE结构中-COO~-密度对其在水泥浆体分散性影响规律表明:PCE分子结构中-COO~-数量越多,分散稳定性越好,水泥硬化所需时间越长,但是对水泥孔隙溶液的Zeta电势影响不大,而共聚物分子结构中-COO~-密度过大将导致水泥初始净浆流动性下降。(3)利用SPSS软件,通过多因素回归分析得出PCE相对分子量对饱和吸附量影响最大。水泥-水-PCE体系中,在低分子量区间段(M_w<40000),PCE分子结构中PEO支链密度越大,其吸附速率越慢,达到平衡时饱和吸附量越大;分子主链越长,其初始吸附能力越强,达到吸附平衡需要的时间越短,且平衡吸附量越大。在高分子区间段(M_w>60000),PCE主链上-COO~-密度越大,达到平衡时饱和吸附量越小,但吸附速率未发生明显变化。(4)水泥-水-PCE体系中,在低分子量区间段,PCE中PEO支链密度越大,水泥浆体初始流动性越好,但不利于水泥浆体的分散稳定性;PCE分子主链越长,越有利于提高水泥浆体的分散力和分散稳定性。在高分子区间段,随着PCE分子结构中-COO~-密度的增加,水泥浆体的初始分散能力出现先增大后减小的规律,而水泥浆体的稳定分散时间延长。(5)蒙脱石-水-PCE体系中,在低分子量区间段,PCE中PEO支链密度越小,其在蒙脱石上的平衡吸附量越少,越有利于减少蒙脱石对PCE的消耗;在高分子量区间段,蒙脱石对PCE的消耗受主链上支链基团密度影响不大。更多还原

【Abstract】 Due to their designable molecular structure,lower required dosage and relatively simple production process,polyether-type polycarboxylate dispersants(hereafter called PCE)have become increasingly popular as additives to mortar and concrete systems.With the development of domestic PCE synthesis technology,there are some urgent problems to be solved in practical engineering applications.Therefore,combing the relationship between PCE synthetic parameters,molecular structure and application performance has become a worldwide research hot and difficult spot.In this paper,the ether PCE was synthesized by APS-SHS as redox initiator and IPEG-2400,AA and MA as the main raw materials.The molecular structure of synthetic copolymer was characterized by FT-IR,~1H NMR,GPC,UV,and DSC.The influences of monomer ratios,initiator and MA dosage on the structure parameters of PCE,and then the effect of structure parameters(PEO density as side chain,carboxylate density and the length of main chain)on the adsorption and dispersion performance of PCE were studied.Research results can be drawn as follows:(1)In the synthesis of AA-IPEG copolymer,the conversion of IPEG increased with the addition of AA and the carboxylate ion density increased with the increase dosage of MA.Besides,the length of PCE main chain became shorter and the relative molecular weight distribution became narrower with the increase of initiator dosage.(2)At same PCE dosage,the effect of carboxylate density in the PCE structure on the dispersion of cement pastes shows that the larger the amount of carboxylate ions in PCE,the smaller the saturated adsorption and the better dispersion stability,the longer it takes for the cement to harden,but it has little effect on the Zeta potential of cement pore solutions and excessive carboxylate density in PCE results in the decrease of the initial cement pastes fluidity.(3)Multiple regression analysis by SPSS software showed that M_w of PCE has the greatest impact on the amount of saturated adsorption.For cement-water-PCE systems,in the low molecular weight intervals(M_w<40000),the higher the PEO side chain density in the molecular structure,the slower the adsorption rate and the greater the saturated adsorption amount at the equilibrium.The longer the molecular main chain of copolymer,the higher the initial adsorption capacity,the shorter the time to reach adsorption equilibrium and the greater the equilibrium adsorption.During the high molecular weight intervals(M_w>60000),the greater the carboxylate ion density on the PCE backbone,the lower its equilibrium adsorption on the surface of cement particle,but the influence on adsorption rate can be ignored.(4)For cement-water-PCE systems,during the low molecular weight intervals,the high PEO side chain density is beneficial to improve the initial fluidity of cement pastes,but not conducive to the dispersion retention of cement pastes.The long length of PCE backbone helps to improve the dispersing force and dispersion retention of cement pastes.During the high molecular weight intervals,with the increase of carboxylate ion on backbone,the dispersing force of cement pastes first increases and then decreases,and copolymers with a high carboxylate ion can be beneficial for cements where a longer setting time is required.(5)For montmorillonite-water-PCE systems,during the low molecular weight intervals,the lower PEO side chain density on backbone is beneficial to reduce the PCE amount adsorbed on montmorillonite,when the adsorption reach equilibrium.During the high molecular weight intervals,the density of side chain group has a minor effect the consumption of PCE by montmorillonite.更多还原