Properties And Microstructure Of Couplingagent And PB-g-PS Latex-Modified Cementmortars

In this paper,polybutadiene grafted polystyrene(PB-g-PS)latex was synthesized by semi-continuous emulsion grafting polymerization.the coupling agent is incorporated into the latex to compound and modify the cement mortar.The effect of coupling agent on hydration of cement was studied by means of FTIR,DSC and TG.The main works as follow:1.Graft copolymers of styrene(St)onto polybutadiene(PB)were prepared via semiconscious seeded emulsion grafting copolymerization method using a redox initiator system.Its mass ratio are 70/30,50/50,and 30/70,respectively.The results were characterized by FTIR and 1H-NMR,and the results showed that the prepared products met the requirements of the experiment.2.Under the condition of fixed water-cement ratio 0.45 and water curing,the different content of coupling agent(the mass ratio of coupling agent to polymer is 0 %,0.3 %,0.6 % and 0.9 %,respectively)were added to PB-g-PS latex with 50/50 mass ratio for modified cement mortar.It is found that the addition of coupling agent has an obvious effect on the properties of mortar.With the addition of coupling agent,the fluidity and water absorption of the modified mortar are greatly improved compared with the ordinary mortar.Then,the effect of coupling agent content and polymer content on the mechanical properties of cement mortar was investigated.The results show that when the polycement ratio is 0,the incorporation of the coupling agent reduces the flexural strength and the compressive strength of the cement mortar.With the increase of the content of the coupling agent,the flexural strength and the compressive strength of the modified mortar tend to increase with the increase of the cement-cement ratio.The flexural strength of the modified mortar is gradually reduced.The compressive strength of the composite modified mortar is larger than that of the latex modified mortar after the cement-cement ratio is more than10%.3.The microstructure of the modified mortar was investigated by SEM.The microstructure analysis showed that the structure of the modified mortar was denser,the dendriform structure and the formation of polymer film were observed.At the same time,the effect of PB-g-PS latex and coupling agent on hydration of cement was studied by means of FTIR,DSC and TG.The results show that when the coupling agent content is0.6 %,the content of calcium hydroxide is the highest.It shows that the addition of appropriate coupling agent can promote the hydration of cement,and the amount of coupling agent is too high,which may bring negative effect.