Influences On Structural Parameters Of Ether-type Polycarboxylate Superplasticizers And Research Of Its Dispersing Properties

Polycarboxylate ether based superplasticizers(PCEs) have become key objects ofresearch institutions from domestic and overseas because of their outstanding designability ofmolecular structure and excellent comprehensive performance. With the progress of thetechnology of ether-type macromonomer in our country, ether-type PCEs compared withester-type PCEs, ether-type PCEs have more advantages in synthetic process andcomprehensive performance. The study focused on influences on structural parameters ofether-type PCEs and influences of its structural parameters(side chain density, main chainlength) on dispersing properties.With oxidation-reduction initiator, ether-type PCEs were synthesized through freeWadicaO cRURO^PeWi_aYiRQ Pade Rf+3(*aQd acW^Oic acid($$)3&(X’ XYWZcYZWaO UaWaPeYeWXwere characterized by gel permeation chromatography(GPC). The results reveal that somekinds of reductants and chain transfer agents may result in lowering the conversion of HPEG,broadening molecular weight distribution (MWD) and worsening the regulation of molecularweight. When the mole ratio of AA to HPEG is4:1, PCEs have the narrowest MWD, asuperior regulating effect of molecular weight and the conversion of HPEG about95%withR as reductant and T as chain transfer agents.A series of ether-type PCEs were synthesized with different n[AA]/n[HPEG] anddifferent dosage of chain transfer agents. Their structural parameters were characterized byGPC. Through theoretical calculation, their side chain density are0.231,0.212,0.192,0.177,0.163respectively, their main chain length varies at the same side chain density.Taking fluidity of cement paste and fluidity of cement mortar as assessment respectively,the article studied the side chain density and main chain length of ether-type PCEs on itsdispersing properties. The results reveal that: side chain density ranging between0.163~0.231,when side chain density is fixed, with the shortening of main chain length, initial dispersingability and disperse-retaining ability increase first and then decrease;the lower side chaindensity is, the better initial dispersing ability could be and the wores disperse-retaining abilitycould be;when side chain density is fixed, the peak of1h’s disperse-retaining ability appearsin the range between500~600of main chain length, the peak of2h’s disperse-retaining ability appears in the range less than500of main chain length.the laws deduced in cement paste canreappear in mortar symtem. However, the best performance points of PCEs in mortar symtemlocate at different positions than that in paste system. In paste system, which2%cement weresubstituted by clay material, PCEs failure seriously with too high or too low side chaindensity. When side chain density is0.192, PCEs have best sodium-bentonite-resisting ability.When side chain density is0.212, PCEs have best kaolin-resisting ability.