Effect of Polymerization Condition on the Slow Release Behavior of Polycarboxylate Superplasticizers
A series of slow release polycarboxylate superplasticizers were synthesized by free radical polymerization under the redox system of hydrogen peroxide and ascorbic acid by using ethylene glycol monovinyl polyethylene glycol ether(EPEG),acrylic acid(AA)and hydroxyethyl acrylate(HEA)as the main raw materials,and 3-mercaptopropionic acid as the chain transfer agent.The effects of synthetic conditions such as feed ratio and solvent on the performance of as-synthesized superpalsticizers.Were ststematly studied.The molecular structure of superplasticizers were characterized by Fourier transfer infrared(FT-IR)spectroscopy,nuclear magnetic resonance(1H NMR)spectroscopy and gel permeation chromatography(GPC).The performance of cement paste and mortar mixed with superplasticizer were tested.The results demonstrate that the synthesized polycarboxylate superplasticizers display large initial fluidity of cement paste and excellent slow release effect when the ratio of acid/ether,alcohol/water,and acid/ester are 3:1,1:2 and 3:1,respectively.
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