Abstract:

The cellulose based copolymer polycarboxylic acid water reducer (HEPCEs) was prepared from natural fiber by grafting etherification, nucleophilic substitution and free polymerization. The molecular structure of synthetic HEPCEs was analyzed by infrared spectrum and gel permeation chromatography. The performance of HEPCEs was tested from the aspects of paste fluidity and time varying fluidity. The mechanism of action of HEPCEs on cement slurry by testing molecular particle size, zeta potential and adsorption layer thickness was further investigated. The results showed that the suitable substitution amount of modified cellulose polyether DBHECs in HEPCEs was 5%—10%. Excessive substitution of DBHECs would lead to branch chain entanglement and hindering the anchoring of carboxylic acid groups, causing a decrease in the performance of the water reducing agent. The introduction of appropriate substitution of cellulose structure can effectively further improve the performance of water reducing agents while maintaining good adsorption performance. From experiments with time variation, HEPCEs-5 indicated good performance and exhibited a certain degree of sustained release effect.

Key words: cellulose polyether, modified, bio-based, polycarboxylate water reducing agent, free radical copolymerization

摘要：

以天然纤维为原料，采用接枝醚化-烯丙基氯双键改性-水溶液自由聚合路线制备纤维素基共聚型聚羧酸减水剂（HEPCEs），通过傅里叶变换红外光谱、凝胶渗透色谱对产品HEPCEs进行分子结构分析，通过净浆流动度、经时变化流动度测试对HEPCEs减水性能进行评价，并同时进行了分子粒径、zeta电位以及吸附层厚度的测试，探究HEPCEs对水泥净浆的作用机理。结果表明，纤维素基共聚型聚羧酸减水剂中改性纤维素聚醚（DBHECs）适宜替代量为5%~10%，过多替代会出现支链缠绕并阻碍羧酸基团锚固，适量替代的纤维素结构引入可以在保持较好吸附性能的同时进一步提升减水剂的性能，超过商用高效减水剂标准，并表现出一定的缓释作用。

关键词: 纤维素聚醚, 改性, 生物基, 聚羧酸减水剂, 自由基共聚