Polycarboxylate Superplasticizers:Mechanism,Synthesis And Characterization

The polycarboxylate superplasticizers(PCEs)are the third generation concrete admixtures.Currently,there is little research about aggregation theory of PCEs,and it becomes a topic containing both significance and challengesto explore aggregation theory ofPCEs.The AA-TPEG copolymers were prepared via free-radical polymerization with KPS as the initiator at 60?for 30 min.The obtained copolymers were characterized by GPC.The molar ratio of the two monomer units in the copolymer and the two unreacted monomer units in the solution were gained to calculate monomer reactivity ratios.The monomer reactivity ratios were calculated by the methods of Mayo-Lewis,Kelen-Tudos and YBR,moreover,this study present nonlinear least squares curve fitting of terminal copolymerization equation(NLLSQ-T)and penultimate copolymerization equation(NLLSQ-P),which used Python NumPy,SciPy and SymPy libraries to generate code and did numerical computations.The monomer reactivity ratios were found to be rAA= 10.888,r'AA= 1.131,rTPEG= 0.012 and r'TPEG =0.042.This study also explored specific copolymerization behavior of similar structure of PCEs with steric hindrance under penultimate copolymerization equation,such as dependence of the mole fractions in the copolymer on the mole fractions of unreacted monomers in the solution,variation of copolymer compositions with conversion and sequence length distribution.The AA-TPEG-type PCEswere prepared via free-radical polymerization with KPS as the initiator and SMAS as chain transfer agent.The obtained PCEs were measured by the fluidity of cement paste.In the process of optimizing the synthesis conditions,the single factor experimental design and FWRN wereapplied.The optimal synthesis conditions were n(AA):n(TPEG):n(SMAS)=3.5:1:0.256,3%quality score of KPS as the initiator at 75?for 4 h 24 min at high conversions,and the FWRN wasbetter than single factor experimental design.The Characterization and Performance of PCEs contains FTIR,GPC,TEM,TG,DLS,contact angle,the fluidity of cement paste,compressive strength of concrete and compounding,and the results showed that physical and chemical properties and the curved shape of PCEs.The PCEs synthesized by FWRN were more excellent at tests of the fluidity of cement paste,compressive strength of concrete and compounding.