Plate–sphere hybrid dispersions: Heterocoagulation kinetics and DLVO evaluation

Dispersed calcium carbonate particles are encapsulated with poly(methyl methacrylate). The optimum condition for the polymerization is investigated; and the encapsulated particles are characterized by spectrophotometric analysis, acid decomposition, thermal analysis, and microscopic observation. From the conversion comparison of the MMA monomer it is found that the optimum concentration of polymerization initiator is 1.58 × 10−3 mol/L. The highest yield of encapsulation is obtained at 250 rpm with a concentration of 0.5 wt % surfactant (sodium dodecyl benzene sulfonate). A comparison of the Fourier transform IR spectra distinctly indicates the formation of PMMA on the surface of the calcium carbonate particles. The outcome of an acid decomposition test proves that the PMMA coating protects the particles. In addition, thermal analyses and microscopic observation characterize the PMMA on the surface of encapsulated particles. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4063–4073, 2004

Poly(methyl methacrylate) encapsulation of calcium carbonate particles

The inorganic/organic core-shell type nanocomposite particles of Al(OH)3/PSt were synthesized through the emulsion polymerization of styrene (St, shell monomer) with ammonium persulfate (APS, initiator), polyoxyethylene (50) nonyl phenyl ether (NP-1050, nonionic surfactant), and ammonium (POE) alkyl arylether sulfate (EU-S133D, anionic surfactant) in the presence of the modified Al(OH)3 particles. The improved compatibility of Al(OH)3 surface with St achieved by the modification with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS) enabled to form a polymer shell around the mineral particles. The structure of nanocomposites prepared from different feed ratio of Al(OH)3/St was investigated by scanning (SEM) and transmission (TEM) electron microscopies.

Synthesis and Characterization of Al(OH)3/Polystyrene Nanocomposite Latex Particles by Emulsion Polymerization

Al(OH)3/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface-functionalized Al(OH)3 particles. Nanosized Al(OH)3 particles were previously functionalized with a silane coupling agent, 3-(trimethoxysilyl) propyl methacrylate (γ-MPS), which was confirmed by FT-IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m−2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)3 core were produced with stable latex emulsion when the weight percents of Al(OH)3 to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)3 nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.

Preparation of Al(OH)3/PMMA nanocomposites by emulsion polymerization

Interfacial-initiated microemulsion copolymerizations of Styrene (St) and N-vinylpyrrilidone (NVP) by the redox initiation couple of cumene hydroperoxide (CHPO) and the presence of the base tetraethylenepentamine (TEPA) were carried out using Tween-80 and n-butanol as the surfactant and co-surfactant, respectively. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were recorded to analyze the chemical composition of latex particles. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) were used to observe the particle morphology and dynamic light scattering (DLS) to determine the particle size. The results demonstrated that interfacial-initiated microemulsion polymerization prompted the copolymerization of water-soluble NVP monomer with oil-soluble St monomer to form core-shell nanoparticles by one-stage.

One-stage Preparation of PSt/PNVP Core/Shell Nanoparticles via Interfacial-initiated Microemulsion Copolymerization

A process was developed for the microencapsulation of inorganic filler particles with poly-methyl-methacrylate, to increase the interaction between the hydrophilic filler particles and a polymer matrix. The filler utilised was aluminium hydroxide with an average diameter of 1.9 microm and a specific surface area of 5 m2/g. The process comprised a surface modification, in which a monolayer of isopropoxy titanium isostearate was chemically bound to the surface to render it hydrophobic and to ensure a chemical bond between the filler and the organic phase. Then, an encapsulation reaction was carried out by means of an emulsion-like polymerization process at monomer starved conditions. The modified particles were stabilized in water with sodium-dodecyl-sulphate. A redox system consisting of cumene-hydroperoxide in combination with sodium-formaldehyde-sulphoxylate and iron(II) salt was applied for the initiation of the polymerization. Besides surface polymer, free polymer particles were also formed. The parameters which varied were the filler concentration, the concentration of the initiator components and the surfactant concentration. At optimum conditions, approximately 50% of the added monomer polymerized at the modified filler surface, thus forming encapsulated filler particles. SEM together with TGA analysis indicated that a smooth polymer layer had been formed on the filler surface. At high filler loading, however, coagulation occurred.

A.M. van Herk

Papers

Encapsulation of aluminium hydroxide fillers with poly-methyl-methacrylate.