Latexes composite

Scotts technology (17) uses fluid-bed (Wurster column) technology to apply polymeric coatings to a number of fertilizer substrates including urea, potassium nitrate, potassium sulfate, and monoammonium phosphate (MAP). The coating material is appHed as a water-borne latex onto the fluidized substrate. As the substrate is fluidized with warm air (40—50°C), water is driven off and the latex coalesces into a continuous film around the fertilizer particle. The particular latex compositions used have selected glass-transition and blocking temperatures, which enable quick removal of the water before the soluble fertilizer core dissolves. This obviates the need to use precoats prior to the latex appHcation. 

A modified latex composition contains a phosphorus surface group. Such a latex is formed by emulsion polymerization of unsaturated synthetic monomers in the presence of a phosponate or a phosphate which is intimately bound to the surface of the latex. Thus, a modified latex containing 46% solids was prepared by emulsion polymerization of butadiene, styrene, acrylic acid-styrene seed latex, and a phosphonate comonomer in H20 in the presence of phosphated alkylphenol ethoxylate at 90°C. The modified latex is useful as a coating for substrates and as a binder in aqueous systems containing inorganic fillers employed in paper coatings, carpet backings, and wallboards [119]. 

A urethane latex composition, (I), was prepared by Kent et al. (1) and used as an in situ delivery agent for 4-hydroxyl-methyl benzoate, which was useful as an image stabilizer. Polyurea, (II), and polyurethane latex compositions were also prepared by the authors (2) containing pendant acid groups as latex stabilizers and as crosslinking sites. 

In a separate investigation by Kent et al. (3) latex compositions containing poly(methyl methacrylate-co-hexyl acrylate) were prepared containing the ultraviolet absorber monomer Norbloc 7966. 

EFFECT OF LATEX COMPOSITION ON THICKENING BY SODIUM LAURYL SULFATE ( 1)... 

Watanebe, T., Tsukiyama, K. and Kawano, T. (1988) Study on Xonotlite-SBR Latex Composite Material. Proceeding of the MRS International Meeting on Advanced materials, Vol. 13. pp. 115-123. 

Thames, S.F. K.G. Panjnani O.S. Fruchey Latex Compositions Containing Ethylenically Unsaturated Esters of Long-Chain Alkenols and Applications Thereof. U.S. Patent 6,897,255 (2005). 

A series of conducting polyaniline/PBSP latex composites was prepared by polymerisation of aniline in the presence of PBSP latex. The mass loading of polyaniline in the composite latex could be controlled by varying the PBSP latex/aniline charging ratio and oxidant/aniline molar ratio. The composites were characterised by elemental analysis, TEM and TGA. The effects of the concentration of the reactants on the conductivity at room temp, and the mechanical properties of the composite films formed from the latices were studied. 12 refs. 

After a lack of interest in these blends for some 20 years, there were some new developments in this field. Thus, protein silver was incorporated in NR to produce antimicrobial latex compositions." Proteins were also used to produce conductive rubber." Collagen protein fibres were incorporated in NR to produce studless tyres exhibiting good properties at low temperatures." Proteins were also cited as potential biofillers for accelerating the biodegradability of blends mainly composed of polyolefins and rubbers." ... 

Sherman et al. fabricated CdS and CdSe/CdS nanoparticles/PS latex composite materials [206]. The nanocrystals were stabilized with poly(cysteine acrylamide) and then bound to polystyrene latex by two different methods. First, anionic 5-nm diameter CdS particles were electrostatically attached to 130-nm surfactant-free cationic PS latexes to fabricate stable dispersions. The PL spectrum showed that the luminescence properties of the latex composite did not depend on the amount of CdS nanoparticles, and that the emission did not change. Another approach to forming CdS and CdSe/CdS nanoparticles/PS latex composites was performed in surfactant-free PS latexes by in-situ polymerization in the presence of nanocrystals. This method was simple and effective, and the size of the latexes was easily tunable. All of these nanocomposite particles were dispersed in water and have a potential application as colloidal crystals for photonic band-gap materials, biological labeling, and optical tracking [206]. 

Ramakrishnan S., McDonald C.J., Carbeck J.D., Prudhomme R.K. Latex composite membranes Structure and properties of the discriminating layer. J. Mem. Sci. 2004 231 57-70 Romero-Cano M.S., Martin-Rodriguez A., Nieves F.J.D.L. Electrosteric stabilization of polymer colloids with different functionality. Langmuir 2001 17(11) 3505-3511 Rau D.C., Parsegian V.A. Direct Measurement of the intermolecular forces between counterion-condensed DNA double helices— Evidence for long-range attractive hydration forces. Biophys. J. 1992 61(1) 246-259... 

The control challenges in emulsion polymerization processes are similar to the ones discussed previously for suspension processes. Different from suspension processes, however, intense research activity has been conducted in the field, aiming to control emulsion polymerization reactions and the final latex properties. It is important to anphasize, though, that the lack of proper instrumentation for online measurement of latex properties has limited the development of control schemes basically to the control of latex composition. In these cases, control schemes depend heavily on the availability of complex process models for in-line evaluation of unmeasured properties, such as the MSD and the PSD. Comparatively, the online control of PSDs has received little attention, and few studies are devoted to this subject. 

Curing Agents. Although SBR latexes often do not require use of curing agents in the normal sense, a number of cure systems are available. For noncarboxylated latex compositions, conventional sulfur systems may be used where external heat can be applied. Otherwise phenolic cures may be used or self crosslinking resins may be blended into the formulation. 

Beadle P, Armes SP, Gottesfeld S, Mombourquette C, Houlton R, Andrews WD, Agnew SF (1992) Electrically conductive polyaniline-copolymer latex composites. Macromolecules 25 (9) 2526-2530... 

A.J. Majumdar, B. Singh and J.M. West, Properties of GRC modified by styrene-butadiene rubber latex , Composites, 1987, 61-64. 

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