Research On Relationship Between Structure And Performance Of Polycarboxylate Superplasticizer

As the outstanding advantage, a key merit to polycarboxylate superplasticizer (PCE)is its structure designability. By researching the relationship between the structure andperformance, different valued properties can be obtained.In order to understand the relationship between the structure and performance,macromonomer with different molecular weight (500,1000,1500,2000,2400and2700respectively and named M500, M1000, M1500, M2000, M2400and M2700)were used to synthesize PCE with gradual changed side chain density and main chainlength. The gel permeation chromatogram (GPC) was used to detect the structure andits availability was proved. Then the different four synthesis technologies werecompared to obtain the proper one. In addition, the best cement paste method wasexplored in order to evaluate the performance accurately. Based on following analysis,the relationship between the structure and performance was discussed.It is found that the technology which adds activated monomer and initiatordropwise can control the structure well and GPC can detect the structure accurately.What’s more, the effective polymer equalmass adding method can evaluate theperformance precisely. Regarding the side chain density, the initial cement pastefluidity firstly increased with the decreasing of side chain length and then tended tobecome smoothly when a certain side chain density was reached and the mechanismwas analyzed. Regarding the effect of main chain length, the mole ratio of chaintransfer agent to macromonomer ([T/E]) should not exceed0.3. In addition, fourdifferent structures were classified based on different main chain length, namelyexcessive short structure, shorter structure, longer structure and excessive longstructure. When keeping the same side chain density, the longer main chain length,the more obvious retarding effect to the cement hydration was observed.Regarding the side chain length, the acid ether ratio was improved to obtain highereffective content with the increasing of side chain length. What’ more, with theincrease of side chain molecular weight, the side chain density to PCE with bestproperty tend to become sparser and the main chain length shorter and vice verse. Itwas found that the molecular weight of PCE with best property always locatedbetween35,000to50,000. The longer side chain length help to improve the PCEproperty, so it provides a direction to increase the PCE performance in the future.