梳状聚羧酸减水剂主链长度对水泥浆体分散性能的影响

Effects of main chain length of comb polycarboxylate superplasticizer on dispersing performance of cement paste

通过自由基热聚合的方法合成了相对分子质量为1.7万～8.3万的一系列羧基密度、侧链长度和侧链密度相同,主链长度不同的梳型聚羧酸减水剂（PC）,通过分析其在水溶液中的分子尺寸、对水泥浆体的Zeta电位、分散、吸附等的影响规律,研究了不同主链长度对PC宏观性能的影响规律.结果表明：当分子质量较小时,吸附量较小,PC的分散性能较差;当分子质量较大时,PC分子发生团聚,影响了空间位阻的有效发挥,PC的分散性能也较差;合适的相对分子质量窗口区间为2万～6万;在此区间内,随着分子质量的增加,分散性能略有提高.

Comb-like polycarboxylate superplasticizer（PC） with different main chain length and same density of carboxylic acid, same side chain length,same side chain density,with molecular weight between 17 000 and 83 000 was synthesized by the method of radical thermal polymerization. The influence law of different main chain length on the particle size of PC in aqueoas solution and the macroscopic properties,for instance,the Zeta potential,dispersion and adsorption of the fresh cement paste were investigat- ed systematically. The results indicate that when the molecular weight is relative small,the adsorption capability is too small to behave good dispersion properties. When the molecular weight is relative large,the molecules reunite,which affects the steric hin- drance effect,so the dispersion property is poor. The appropriate window for molecular weight is between 20 000 and 60 000. Within this range,with the increase of the molecular weight,the dispersion property increase slightly.