An experimental investigation of the stability of ethylcellulose latex: correlation between zeta potential and sedimentation.
ABSTRACT This paper aims at explaining the experimental observations of the stability and redispersibility of an aqueous ethylcellulose latex through the electrokinetic characterization of the particles. The surface charge and the electrical double layer thickness play an essential role in the stability of the system, hence the need for a full characterization of the polymeric particles. The effect of both pH and ionic strength of the dispersion medium were investigated. It was found that at acid pH values the latex displays "delayed" or "hindered" sedimentation: in such conditions, the electrophoretic mobility and zeta potential are rather low, indicating a small electrokinetic charge on the particles. At alkaline pH, when the dissociation of ionizable surface groups must be complete, the zeta potential is high and negative. The electrostatic repulsion between polymer particles is responsible for the low sedimentation volume and poor redispersibility of the latex. The effect of NaCl and CaCl(2) concentration on both the zeta potential and stability of the latexes was also investigated: it was found that CaCl(2) has the greatest influence, yielding flocculated, easily re-dispersible systems when its concentration in the dispersion medium is high enough. There qualitative observations were ascertained by means of calculations of the potential energy of interaction between particles. In the case of NaCl solutions, a high and relatively wide potential energy barrier was predicted, that may prevent the particle aggregation. Above 5mM NaCl a shallow minimum in the potential energy curves must lead to the formation of aggregates. Similar results were found with CaCl(2) solutions, although in this case the secondary minima are deeper and appear at lower concentrations.
- SourceAvailable from: Mladen LadikaColloids and Surfaces A Physicochemical and Engineering Aspects 10/2014; 459:274–281. · 2.35 Impact Factor
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ABSTRACT: The cationic poly(vinyl acetate-butyl acrylate-DMC) copolymer emulsions were successfully prepared using the emulsion polymerization technique with 2-methylacryloylxyethyl trimethyl ammonium chloride (DMC) as a functional cationic monomer, cetyltrimethylammonium bromide (CTAB) as the surfactant, and K2S2O8 as the initiator. The morphology, structure and composition, and thermal properties of the emulsions were characterized by TEM, FTIR and DSC, respectively. Also, the correlations between the particle size, zeta potential, viscosity, water absorption and antibacterial efficiency of prepared cationic emulsions and DMC cationic monomer content were established. The results show that the content of the DMC monomer could affect the properties of the emulsions and their films significantly. This offers an attractive opportunity for adjusting the particle size and zeta potential of cationic emulsions over a wide range by feeding DMC monomer in varying concentrations. Furthermore, the prepared emulsions present a high antibacterial efficiency of 98.2% even containing only 2.0 wt% DMC in its monomers, which results in a great potential application as a kind of antibacterial coating material in the future.Journal of Macromolecular Science Part A 01/2013; 50(2). · 0.74 Impact Factor
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ABSTRACT: The cationic poly(vinyl acetate-butyl acrylate-2-hydroxyethyl acrylate) terpolymer latexes (Poly(VAc-BA-HEA)) were successfully prepared using the emulsion polymerization. The structure and composition, morphology, and thermal property of the latexes were characterized by FTIR, TEM and DSC, respectively. Also, the correlations between the particle size, zeta potential, viscosity and water absorption of prepared cationic latexes and 2-hydroxyethyl acrylate concentration were established. The results show that the concentration of 2-hydroxyethyl acrylate could affect the properties of the latexes significantly. This offers an attractive opportunity for adjusting the particle size and viscosity of latexes over a wide range by feeding 2-hydroxyethyl acrylate with varying concentration.Polymer-Plastics Technology and Engineering 10/2013; 52(13). · 1.48 Impact Factor