Colloidal properties of latexes

Abstract Emulsion homopolymers and copolymers (latexes) are widely used in architectural interior and exterior paints, adhesives, and textile industries. Colloidal stabihzators in the emulsion polymerization strongly affect not only the colloidal properties of latexes but also the fdm and mechanical properties, in general. Additionally, the properties of polymer/copolymer latexes depend on the copolymer composition, polymer morphology, initiator, polymerization medium and colloidal characteristics of copolymer particles. 

It has been proved that incorporation of carboxylic acid groups in the polymeric chain has a significant effect on colloidal properties of latex, processability, and end-use property. Carboxylated styrene-butadiene latexes (XSBR) are prepared via batch emulsion copolymerization with different amounts of acrylic acid in the absence of emulsifier. They are among the most important polymeric colloids, and can be used as binder in paper coatings, carpet backing, paints, and nonwoven. There are several studies on the preparation and properties of XSBR latexes. 

Latex-modified mortar and concrete have a markedly improved water retention over ordinary cement mortar and concrete. The water retention is dependent on the polymer-cement ratio. The reasons for this can probably be explained in terms of the hydrophilic colloidal properties of latexes themselves and the inhibited water evaporation due to the filling and sealing effects of impermeable polymer films formed. Accordingly, a sufficient amount of water required for cement hydration is held in the mortar and concrete and, for most latex-modified systems, dry cure is preferable to wet or water cure. This is also examined in Sec. 2.1. 

Ottewill RH (1990) Colloidal properties of latex particles. In Candau F, OttewiU RH (eds) An introduction to polymer colloids. Kluwer, Dordrecht, pp 129-158... 

The colloidal properties of latex products are of great importance from both academic and industrial points of view. Some representative charaeteristics include the particle size and particle size distribution, the particle surface charge density (or zeta potential), the particle surface area covered by one stabilizer molecule, the conformation of the hydrophilic polymer physically adsorbed or chemically couplet onto the particle surface, the type and concentration of functional groups on the particle surface, the particle morphology, the optical and rheological properties and the colloidal stability. 

The outstanding colloidal properties of latex particles which can be tuned in a wide range of size, shape, surface charges and fiinctionahties make them very attractive in quite a lot of... 

The major distinction between the model of La Mer and that developed for uniform latex particles lies in the incorporation of colloidal stability of small particles. The La Mer model assumes that each nucleus is colloidally stable and survives at the end of the reaction at the center of a particle. The aggregation models argue that stabilizing primary small particles is difficult, but aggregation does not necessarily result in a broad particle-size distribution. When schemes for control of particle-size distribution are developed, the result of accepting the notion that colloidal stability can play an important role is that attention is focused away from the length of the nucleation period and towards the colloidal properties of the growing particles. 

Emulsion polymers have been used in a broad range of applications because of their environment-friendly nature and the versatility of the process for adjusting both macromolecular and colloidal properties of the latex. Out of the worldwide demand of emulsion polymers, 23% is used for surface sizing and coating of paper and paper board, 20% for paints and coatings, 25% for adhesives and sealants, and 9% for carpet backing [234], References 234 and 235 and several chapters of the book edited by Lovell and El-Aasser are devoted to the major industrial uses of emulsion polymerization and polymer latexes. 

El-Aasser M.S, Makgawmata T, VanderHoff, J.W (1983) Batch and Semicontinuous Emulsion Copol3dnerization of Vinyl Acetate-Butyl Acrylate. 1. Bulk, Surface and Colloidal Properties of Copol)nner Latexes. J. Polym. Sci. 21 2363-2382. 

The above latices were prepared by batch precipitation polymerisation of N-isopropylmethacrylamide using methylenebisacrylamide, as crosslinker, and potassium persulphate, as polymerisation initiator. The effect of the crosslinker on total conversion of polymer, latex particle size and morphological properties and colloidal properties of the final microgel particles were investigated. The relationship between the amount of water-soluble polymer and amount of crosslinker and the influence of temperature on the electrophoretic mobility of the latex are considered. 11 refs. 

As a result of his many publications on the colloidal properties of rubber latex, including Latex (1947), Colloidal Chemistry of Rubber (1928), Colloidal Phenomena (1939), Experiments on Colloid Chemistry (1940) and Silicia Science (1955) and his editorship of Handbuch der Gesamten Kautschirktechnolc e, he became recognized as ont of tire world s leading latex chemists. 

TABLE 13.1 The Change of Colloid-Chemical Properties of Latex and Indian Rubber in the Process of Ozonization... 

To prepare stable PVC latexes by emulsion polymerization of VC, considerable attention must be paid to the choice of a proper emulsifier. The emulsifier greatly affects the reaction kinetics and the physico-chemical and colloidal properties of the final polymer product and/or the dispersion [98]. The choice of the proper emulsifier is a complex problem because of its manifold functions, e.g. the surf ace tension of the aqueous solution, emulsification or solubilization of oil-soluble monomers or additives, and the protection of latex particles against flocculation [99]. 

There is no doubt that the discipline of interfacial phenomena is an indispensable part of emulsion polymerization. Thus, the goal of this chapter is to offer the reader an introductory discussion on the interfacial phenomena related to the emulsion polymerization process, industrial emulsion polymerization processes (primarily the semibatch and continuous reaction systems), some important end-use properties of latex products, and some industrial apphcations. In this manner, the reader may effectively grasp the key features of emulsion polymerization mechanisms and kinetics. Some general readings in this vital interdisciphnary research area [1-6] are recommended for those who need to familiarize themselves with an introduction to the basic concepts of colloid and interface science. 

Among aU these various polymerization processes, one major advantage of emulsion polymerization techniques is that according to the selected recipe, it is really possible to carefully adjust both macromolecular and colloidal properties of the obtained latexes, which is quite versatile in view of the variety of applications. For specialty ones, the control of particle size, particle size distribution, surface morphology, surface chemistry and functionality etc. is indeed of paramount importance. In that purpose, emulsion polymerization has long been proved to be appropriate in the synthesis of functional latex particles (Arshady, 1999 Kawaguchi etaL, 2003). 

El-Aasser, M.S., Makgawinata, T., Vanderhoff, J.W., and Pichot, C. 1983. Batch and semicontinuous emulsion copolymerization of vinyl acetate-hutyl acrylate. I. Bulk, surface, and colloidal properties of copolymer latexes. J. Polym. Sci. Polym. Chem. Ed. 21 2363-82. 

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