Dispersion Polymerization Of Low-charge-density Polyacrylamide In Aqueous Solution Of Ammonium Sulfate

In recent years, the water-soluble polymers via aqueous dispersion polymerization have been widely used in the fields of wastewater treatment, enhanced oil recovery (EOR), pulping and papermaking and so on. Herein, the progress of the low-charge-density polyacrylamide with positive and negative charges via aqueous dispersion polymerization has been revealed. The solution properties, swelling and thixotropy behaviors, flocculation were initially investigated. The results indicated that the dispersion may be tailored for the potential applications as viscosifier or flocculant.The low-charge-density amphoteric terpolymers (denoted as D-amPAM) composed of acrylamide (AM), acrylic acid (AA) and 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) were prepared via free-radical dispersion polymerization in the aqueous ammonium sulfate media using 2, 2'-azobis (2-methylpropionconidine) dihydrochloride (V-50) as initiator and poly (2-methylacryloylxyethyl trimethyl ammonium chloride) (PDMC) as cationic polymeric stabilizer. The effects of the stabilizer concentration and viscosity-average molecular weight thereof, ammonium sulfate concentration, comonomer concentration and molar ratio thereof, initiator concentration, pH, polymerization temperature, stirring speed, polymerization time, chelator disodium ethylenediamine tetraacetic acid (EDTA·2Na) concentration and chain-transfer agent isopropyl alcohol (IPA) concentration on the dispersion system were systemically investigated. The intrinsic viscosity, monomer conversion, apparent (bulk) viscosity, colloidal particle size and the apparent morphology thereof were measured via Ubbelohde viscometer, rotary viscosimeter, laser particle size analyzer, transmission electron micrograph (TEM) and cold field emission scanning electron microscope (SEM), respectively; and the amPAM structure and composition were characterized by Fourier Transform Infra-Red (FTIR) and NMR spectrometer. A dispersion stabilization theoretical model of the dispersion stability was proposed by considering the morphologies of the TEMs of redispersed particles and the dispersion apparent characters, and the"ionic cloud layer"model was further validated by quantitatively analyzing the thixotropy strength of D-amPAM.The solution properties of D-amPAM were studied with Ubbelohde viscometer, rotary viscosimeter and Zetasizer Nano ZS90 by variation of the polymer concentration, salt concentration and type thereof, and temperature. The acrylamide-based dispersion swelling properties were also been comparatively studied with the AS concentration. The results were as follows: The network structures might be formed by the amPAM and PDMC chains in the D-amPAM solutions. In D-amPAM solutions, it was found that the influences of hydrogen bonds, the relationships between PDMC and amPAM chains, the micro-environmental salt concentrations around the polymer chains, typically the network structures formed by the effects of salt (Mg2+) and PDMC chain bridges and micro-aggregation in the solution, played important roles which directly relieved the transitions of polymer chain conformation. And the linear manner of the reduced viscosities was different and complicated as a function of the D-amPAM concentration in different concentration of NaCl media or at different temperature conditions. In concentrated solutions, the data of apparent viscosities and apparent phenomena indicated that the phase-separation behaviors (solution and swollen phases) occurred when the D-amPAM concentrations exceeded 1.92 g/dL, and the solutions exhibited typically pseudo-plastic viscosity profiles. The acrylamide-based dispersion solution or swelling behaviors as a function of AS concentration were markedly different, mainly depending on the comonomer molar ratios.From the rheological point of view, the studies on the effects of PDMC concentration and viscosity-average molecular weight thereof, steady shear rate, ammonium sulfate (AS) concentration, comonomer concentration and composition thereof on the D-amPAM thixotropy behaviors and thixotropy strengths, which indicated the information of dispersion microstructure. The thixotropy testing results well represented the dispersion apparent characters, which was first reported by the lecture.In the last chapter, the D-amPAM flocculation for 2.0 wt% kaolin suspension were carried out via variation of the D-amPAM concentration and intrinsic viscosity thereof, pH and flocculation temperature and so on. Through these experiments, D-amPAM could be used as an effective polymer flocculant.