Studies Of Preparation Of Organic-montmorillonite As Rheological Agent In Coatings And Intercalation Mechanism

In recent coating industry markets,there are many kinds of rheological agent of coatings,but each of them has its advantages and disadvantages.Therefore,the development of a new type of additive with higher rheological performance becomes an important issue.Based on the analyses of the Elements Construction Additive Product Bentone SD-1,cationic surfactant cetyl trimethylammonium bromide(CTAB),anionic surfactant sodium dodecyl sulfate(SDS),and nonionic surfactant hydrogenated castor oil(MT)intercalated na-montmorillonite(MMT)were prepared by solution method and dry method(dry ball milling).The influences of surfactants and their added orders on montmorillonite’s structure and rheological performance were investigated.To verify the interaction mechanism between three kinds of surfactants and montmorillonite,different quaternary ammonium salts intercalated montmorillonites were prepared by dry method and half-dry method.The effects of carbon chain length of different quaternary ammonium salts and types of MMT were studied.Meanwhile,molecular dynamics simulations have been performed to investigate the intercalation processing of surfactants into the MMT interface.The results showed that new types of rheological agent named CTAB-SDS-MT-MMT and(CTAB,SDS)-MT-MMT with higher performance than BentoneSD-1 were successfully prepared.The suggested processing for organic-MMT as rheological agent in coatings is three-steps intercalated solution method(CTAB-SDS-MT-MMT),i.e.,surfactants added order is CTAB/SDS/MT.The processing conditions are suggested as follows:the dosage of CTAB= 1.2 CEC,SDS=0.2CEC,MT=0.2CEC,the slurry concentration =10%,the constant temperatures= 80℃,the stirring time=3h(each surfactant stir 1h).Surfactants and their added orders played an important role in the structure of organic-montmorillonite.The intercalation effect greatly depended on CTAB,it could be intercalated into MMT interlayer mainly due to the substitution of the exchangeable cations in the MMT interlayer,SDS and MT could not be intercalated into MMT interlayer but could help CTAB make the structure of organic MMT more stable and ordered.The processing conditions for organic-MMT by dry ball milling are suggested as follows:the dosage of surfactant= 1.2 CEC,the ball mill speed=400r/min,the ratio of ball to raw materials=1:20,the ball mill time=lh.The results testified that CTAB,SDS and MT could not be intercalated into MMT interlayer whether used single or composite surfactant to intercalate MMT by dry ball milling;when used composite of three kinds of them as modifier,the largest basal d(001)-spacing of MMT was about 4.85nm.The results also indicated that the interaction effect of MMT was affected by the carbon chain lenth of surfancts,the interlayer capacity of divalent cations,the interlayer water content and the interlayer environment of MMT.The intercalation effect of MMT increased in an organic interlayer environment with decreasing the carbon chain lenth and increasing the interlayer capacity of dicalent cations and interlayer water content.The results of molecular dynamics simulations testified that the existence of different arrangements of surfactants in the interlayer of MMT,and vividly recreated the processing of the exchange reaction between cationic surfactant and the exchangeable cations in MMT.The results of molecular dynamics simulations also testified that the existence of water in the MMT interlayer was helpful to the intercalation effect.And by the existence of water molecules,CTAB would be interacted with SDS by electrostatic interaction forming mixed micellar aggregates,then intercalated into MMT interlayer.