Molecular Design of an Allylether PCE with Enhanced Clay Tollerance
Yue Zhang, Lei Lei
Appears on pages(s):
polycarboxylate superplasticizers; Ca2+ binding; montmorillonite; adsorption
The sensitivity problem of polycarboxylate superplasticizers (PCEs) toward clay contaminants becomes more and more severe nowadays. The negative impact of clay contaminants, especially montmorillonite (MMT) on PCEs is stemming from the intercalation of polyethylene glycol side chains into the interlayer gallery of montmorillonite. In this study, two PCE polymers were synthesized from the same α-allyl ω-hydroxy poly (ethylene glycol) (APEG) macromonomer with designated side-chain lengths of 7 EO units, but different acids as co-monomers, namely, maleic anhydride (MA) and acrylic acid (AA). These two APEG PCEs were designed such as to possess the same anionic charge amounts and similar molecular weights. The dispersing performance of the two polymers was tested in the absence and presence of montmorillonite clay. It turned out that AA-7APEG exhibited much better clay tolerance as compared to that of MA-7APEG. To further investigate the interaction mode between PCEs and montmorillonite, XRD and adsorption measurements were carried out. Additionally, the Ca2+ binding capacity of the two PCE polymers was probed via charge titration experiments. The results show that MA-7APEG could chelate more calcium cations and thus lead to decreased anionic charge density and also reduced electrostatic repulsion towards MMT.