RAFT法合成聚羧酸减水剂及分子量参数对其应用性能影响的研究

发布时间：2018-03-19 01:34

  本文选题：聚羧酸减水剂　切入点：RAFT法　出处：《华南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：聚羧酸减水剂(PCEs)具有减水率高、保坍性好、分子结构可设计性强和节能环保等特点,一经问世便得到迅速发展,目前在中国已经占据了超过一半的减水剂市场份额。PCEs的合成一直采用自由基聚合的方法,该方法合成的聚合物分子量分布较宽(多分散性PDI1.5),研究分子量与性能之间的关系时缺乏说服力。可逆加成-断裂链转移聚合(RAFT)是一种比较新的可控/活性聚合方法,合成的聚合物分子量分布窄、分子量大小易调节,目前主要应用于非水溶性的星型、梳型等结构特殊的聚合物合成中,在合成水溶性聚合物方面应用较少。PCEs是一种水溶性交联接枝聚合物,对聚合条件的要求更为特殊。本文根据RAFT法可控聚合的原理,合成出不同分子量及分子量分布的PCEs,探讨了合成工艺影响因素,并考察了分子量及分子量分布对其应用性能的影响规律。主要的研究内容及结果如下:1、合成S-S'-二(a,a'-二甲基-a"-乙酸)-三硫代碳酸酯(BDATT)RAFT试剂,以现有常用原料合成PCEs,通过考察聚合温度、小单体与RAFT试剂共同滴加时间、引发剂滴加时间等参数对分子量分布及单体转化率的影响规律,优化RAFT法合成PCEs的聚合工艺。本聚合系统中,聚合温度为80℃,引发剂水溶液与BDATT的丙烯酸水溶液同时滴加3h的条件下得到的PCEs单体转化率高(75%以上)且分子量分布窄(多分散性普遍低于1.3)。2、考察不同种类引发剂、引发剂掺量、引发剂与RAFT试剂的掺量比例对PCEs分子量参数的影响规律。偶氮二异丁基脒二盐酸盐(AIBA)引发合成的PCEs比同条件下过硫酸铵(APS)引发聚合的PCEs分子量分布更窄且单体转化率更高;同等RAFT试剂掺量下,引发剂浓度越高,PCEs分子量分布越宽,单体转化率越高;改变引发剂与RAFT试剂的掺量比发现随着RAFT试剂浓度的升高,聚合物的分子量分布变窄,分子量逐渐减小。3、对RAFT法合成的不同分子量和不同分子量分布的PCEs进行应用性能测试,结果表明分子量大小对水泥净浆流动度、水泥胶砂减水率、水泥砂浆扩展度及水泥砂浆含气量影响很大。本聚合系统合成的PCEs样品多分散性系数(PDI)均小于1.35,在该条件下,具有最佳的净浆流动性及流动保持性能的PCEs重均分子量(Mw)大约在81000至89000之间,胶砂减水率最高的PCEs重均分子量大约在80000到100000之间,具有最佳砂浆扩展度的PCEs重均分子量大约在70000至88000之间,基本确定具有最佳应用性能的PCEs重均分子量在80000至88000之间。砂浆含气量随分子量的降低逐渐升高,分子量越大的PCEs经时损失越小。分子量相同时,分子量分布窄的PCEs分散性能更优。
[Abstract]:Polycarboxylic acid water reducer (PCEs) has the characteristics of high water reducing rate, good collapsibility, strong design of molecular structure, energy saving and environmental protection. At present, more than half of the market share of water reducers. PCEs have been synthesized by free radical polymerization in China. The polymer synthesized by this method has a wide molecular weight distribution (polydispersity PDI 1.5), which is not persuasive in studying the relationship between molecular weight and properties. Reversible addition-break chain transfer polymerization (Raft) is a new controllable / active polymerization method. The molecular weight distribution of the synthesized polymers is narrow, and the molecular weight is easy to adjust. At present, the synthesized polymers are mainly used in the synthesis of insoluble star and comb polymers with special structure. The application of PCEs in the synthesis of water-soluble polymers is less. PCEs is a kind of water-soluble crosslinked grafted polymers, and the conditions of polymerization are more special. In this paper, according to the principle of controllable polymerization by RAFT method, PCEs with different molecular weight and molecular weight distribution were synthesized. The effects of molecular weight and molecular weight distribution on its application properties were investigated. The main research contents and results were as follows: 1. The synthesis of S-Sz-dimethyl-a "-dimethyl-a" -trithiocarbonate BDATTURAFT reagent, the main research contents and results were as follows. PCEs were synthesized from common raw materials. The influence of polymerization temperature, the time of dropping small monomer and RAFT reagent and the time of initiator dropping on the molecular weight distribution and monomer conversion were investigated. The polymerization process of PCEs was optimized by RAFT method. In this polymerization system, the polymerization temperature was 80 鈩，

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