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玉米淀粉经酸解处理后,经次氯酸钠氧化、环氧乙烷醚化,制备出氧化-醚化淀粉,对其在水泥中的减水分散效果进行了研究,并通过红外光谱、流变仪及zeta电位等测试对其改性效果进行表征。结果表明:玉米淀粉分子链上被成功引入了羧基和羟乙基醚,在羧基含量为0.48%时醚化度(摩尔取代度MS)为0.5时减水剂分散能力最好。相同掺量下,氧化-醚化淀粉型减水剂减水效果明显优于萘系减水剂。氧化-醚化淀粉掺量为0.6%～0.8%时,减水效果最好。氧化-醚化淀粉的zeta电位值为-11.4mV明显低于萘系的-36.7mV,说明其减水分散能力是通过阴离子羧酸基团的吸附作用,并主要靠较大分子量及其分子链中葡萄糖单元环的空间位阻来分散水泥颗粒。
The oxidized etherified starch was prepared by the oxidative treatment of corn starch with sodium hypochlorite and etherified by ethylene oxide. The water reducing and dispersing effect of the starch in the cement was studied. zeta potential and other tests to characterize the modification effect. The results showed that carboxyl group and hydroxyethyl ether were successfully introduced into the molecular chain of corn starch, and the superplasticizer had the best dispersibility when the degree of etherification (molar degree of substitution MS) was 0.5 when the carboxyl group content was 0.48%. Under the same dosage, the water reducing effect of oxidized-etherified starch superplasticizer is better than that of naphthalene superplasticizer. Oxidation - etherified starch content of 0.6% to 0.8%, the best water reduction. The zeta potential of the oxidized-etherified starch was -11.4 mV, which was significantly lower than that of the naphthalene-36.7 mV, indicating that the water-reducing and dispersing ability of the oxidized-etherified starch was determined by the adsorption of anionic carboxylic acid groups and mainly by the larger molecular weight and its molecular chain The steric hindrance of the glucose unit ring disperses the cement particles.