EFFECT OF DIESTER IN ESTERIFICATION PRODUCT OF POLYETHYLENE GLYCOL AND ACRYLIC ACID ON THE PERFORMANCE OF POLYCARBOXYLATE SUPERPLASTICIZER

Ester-based polycarboxylate superplasticizer was produced by esterification product of polyethylene glycol and acrylic acid. Variation law of polyethylene glycol di-acrylate content accompanying with esterification ratio and side effect to performance of polycarboxylate superplasticizer was studied by reversed-phase high performance liquid chromatography. Experimental results showed that both polyethylene glycol mono-acrylate and polyethylene glycol di-acrylate existed in the esterification product. Ratio of di- and mono-acrylate contents sharply rose when esterification ratio increased. When esterification ratio was 26 %, there was a certain amount of di-acrylate. When esterification ratio of the system was 85 %, the content of di-acrylate was 18.5 %, ratio of di-ester and mono-ester contents was 0.38, while the highest fluidity of cement paste with the addition of polyacrylate superplasticizer was obtained as 275 mm. And when esterification ratio was more than 109 %, di-acrylate content increased more rapidly, while increment of mono-acrylate content slowed down and even began to decrease. Increment of di-acrylate content caused not only cross-linking of polycarboxylate superplasticizer but also its gelation, which affected the performance of polyacrylate superplasticizer. Based on these works, purified mono-acrylate was used to produce polyacrylate superplasticizer, by which fluidity of cement paste were all above 300 mm and obviously better than the polyacrylate superplasticizer synthesized by unpurified esterification product.