Oya Atıcı

The effect of SDS surfactant on the flow and zeta potential of bentonite suspensions

Abstract The influence of the surfactant on the flow behaviour of bentonite suspensions (2% w/w) was studied for an anionic surfactant, sodium dodecyl sulphate (SDS). In the range of 10 −4 –10 −2 mol/l, SDS was added to the bentonite water system in eight different concentrations and the observed result was the different effects on the viscosity, which is related to the interactions among particles and surfactant, particles and particles, and particles and water molecules. IR studies have been carried out in parallel to the viscosity and zeta potential studies. Based on the structural changes due to the SDS additions, the rheological and colloidal properties of the altered bentonite–water systems have been interpreted.

Graft Copolymerisation of Methyl Methacrylate onto a Bacterial Polyester Containing Unsaturated Side Chains

Poly(3-hydroxy alkanoate) containing unsaturated side chains was produced by feeding Pseudomonas oleovorans with soybean-soil acid (PHA-soybean). The composition of PHA-soyebean were found to be 10 mol-% of unsaturated side chains with the saturated hexanoate, octanoate and decanoate units. Methyl methacrylate (MMA) was thremally grafted on PHA-soybean in the presence of benzoyl peroxide. Fractional precipitation was used to isolate the grapht copolymer from related homopolymers. PHA content in copolymer samples was between 15 to 30 mol-%. Graft copolymer samples were kept in hydroquinone to prevent post polymerization leading to crosslinking in a day under laboratory atmospheric conditions. Copolymer characterization was performed using GPC and NMR techniques. Thermal analysis of the graft copolymer indicated the decomposition and glass transition temperatures of the PHA and PMMA segments of the graft copolymers. They also showed elongation at break in the range 10 to 21 related to the plasticizer effect of the biopolyester segments.

Synthesis of block copolymers via redox polymerization

Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen-containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s-b-polyacrylonitrile, poly(ethylene glycol)s-b-poly(acrylonitrile-co-vinyl acetate), poly(ethylene glycol)s-b-polyacrylamide, poly(ethylene glycol)s-b-poly(acrylamide-co-vinyl acetate), poly(1-chloromethyl ethylene glycol)-bpoly(acrylonitrile-co-vinyl acetate), and bis[poly(ethylene glycol terephthalate)]-b-poly(acrylonitrile-co-vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed.

Interactions of BDTDACl and DTABr Surfactants with Montmorillonite in Aqueous Systems

In this study, the effect of the two cationic surfactants (benzyldimethyltetradecylammonium chloride (BDTDACl) and dodecyltrimethyl-ammonium bromide (DTABr)) on the electrokinetic and rheologic properties of Na-montmorillonite dispersion (3% w/w) has been investigated at their concentrations between 0 and 10 mmol/L. Experimental results reveal that cationic surfactants are attached on the surface of negatively charged clay particles and also they penetrate into the interlayer of clay particles. The intercalation of surfactants with clay minerals is shown to lead to an increase in the interlayer spacing of montmorillonites by X-ray diffraction. The Fourier transform infrared (FTIR) spectra obtained from the modified bentonite products reveal the characteristic absorption bands. The morphology of bentonite dispersions was analyzed by scanning electron microscopy (SEM). Both X-ray diffraction data and scanning electron micrographs of intercalated montmorillonites indicate that most of the montmorillonites are dispersed randomly in the organo-clay dispersion.