Emulsion polymerisation Applications

In the early days of the commercial development of PVC, emulsion polymers were preferred for general purpose applications. This was because these materials exist in the form of the fine primary particles of diameter of the order of 0.1-1.0 p,m, which in the case of some commercial grades aggregate into hollow secondary particles or cenospheres with diameters of 30-100 p,m. These emulsion polymer particles have a high surface/volume ratio and fluxing and gelation with plasticisers is rapid. The use of such polymers was, however, restricted because of the presence of large quantities of soaps and other additives necessary to emulsion polymerisation which adversely affect clarity and electrical insulation properties. 

Emulsion Polymerisation and Applications of Latex, Christopher D. Anderson and Eric S. Daniels, Emulsion Polymers Institute. 

Report 158 Geosynthetics, David I. Cook Report 159 Biopolymers, R.M. Johnson, L.Y. Mwaikambo and N. Tucker, Warwick Manufacturing Group Report 160 Emulsion Polymerisation and Applications of Latex, Christopher D. Anderson and Eric S. Daniels, Emulsion Polymers Institute... 

Emulsion polymerisation has been also extensively employed for the production of molecularly imprinted core-shell particles. This application is discussed in detail in Sect. 2.2.3. 

Applications. At present there are very few known applications, although the surfactants have significant potential due to their unique properties. Sulphonated fatty acids are used in some hard-surface cleaning formulations where their low foam is a benefit and in emulsion polymerisation, where they perform similarly to LAS but with greatly reduced tendency to foam. Future applications for these products may include machine dishwash, extended use in detergent products and industrial applications such as pigment dispersants. For these to be realised, further process development will be required to give a more consistent and better defined product. 

The dominant position of conventional emulsion polymerisations in the preparation of polymer colloids is unlikely to change. However, studies of new routes for preparation of polymer colloids are essential for growth of the industry and to meet the increasing demand for replacement of solvent-borne coatings. Thus, there is great scope for the development of less conventional routes to polymer colloids and the application of newer methods of polymer synthesis to preparation of polymer colloids will undoubtedly be a fruitful area for research. 

Urban D, Schuler B, Schmidt-Thilmmes J. Large-volume applications of latex polymers. In van Herk A, editor. Chemistry and Technology of Emulsion Polymerisation. Oxford Blackwell Publishing 2005. p 226. 

The direct analysis of the organic phase of an emulsion polymerisation is possible. Quantification involves using the bending mode peak of water, which makes up the bulk of the reaction medium, as an internal standard. The process is demonstrated for MMA but is generally applicable to emulsion polymerisations. It does not require the introduction of an extraneous internal standard component into the reaction mixture (319). 

Reactions in micelle system are usually difficult for synthetic applications because of the problems in handling emulsions and the need for careful regulation of concentrations. However, there are many instances (e.g. emulsion polymerisation) where micelle systems are highly useful and are applied on a commercial basis. 

There is an enormous range of industrial applications. For the main part, latexes are prepared by emulsion polymerisation. The process was developed industrially during the last World War as a way of replacing natural rubbers. Much fundamental and applied research has gone into this area. The relevant reaction mechanisms and physical processes have been quite well understood, although a few minor points of controversy are still discussed in the literature [6.4],... 

Microemulsion processes may well find applications in areas which have traditionally used emulsion polymerisation. At the present stage of research, it is mainly water-in-oil microemulsion polymerisation which offers the most possibilities and several patents have been taken out [6.5]. This process minimises certain problems encountered in classic inverted emulsions, namely instability of the latexes they produce, large polydispersity of polymer particles, and the large quantity of coagulum which increases production costs. Water-soluble (co)polymers prepared in microemulsion polymerisation can be used in various ways ... 

This article will provide a general overview of the emulsion polymerisation process and explain how the resulting latexes are used in industrial applications. An introduction to the basic concepts of emulsion polymers will be given, followed by a description of the various production processes and characterisation methods. The classes of emulsion polymers will be surveyed, and the commercial technologies and potential future uses discussed. A number of comprehensive texts on emulsion polymers are available for more in-depth study (60, 89, 94,95, 364, a.l-a.ll). 

Flexibility is the key word in emulsion polymerisation. Latex properties can be tailored to the application (65,384). Various types of monomers, processing methods, and additives can be used during emulsion polymerisation, making the process flexible (276). A wide variety of products with specialised properties can be manufactured. Emulsion polymerisation allows for the production of particles with specially-tailored properties, including size, composition, morphology, and molecular weight. Functional groups can also be incorporated (160). Blends of different types of latexes have been formulated to provide the desired properties without copolymerisation (139,156, 213, 386). 

Hybrid (or composite) latexes (169) are essentially a combination of the artificial latex and emulsion polymerisation methods (68, 167). A water-insoluble species (such as polymer) may be dissolved in monomer and dispersed in water in the same marmer as the artificial latexes. However, rather than removing the monomeric solvent, it is polymerised in the droplets by the addition of initiator. The monomer-swollen polymer particles capture radicals and polymerise to form a polymeric blend or structured domains. In this maimer, polystyrene particles with styrene-butadiene mbber (SBR) inclusions have been prepared for impact modification applications. 

Monomers are of principal interest in emulsion polymerisation, and must be chosen based on the performance requirements of the intended application. Cost is another critical factor in the selection of an appropriate monomer. The monomer cannot be completely miscible with the water phase (otherwise it would be a dispersion polymerisation), nor can it be completely insoluble (or polymerisation by conventional emulsion polymerisation could not proceed). Most monomers are sparingly soluble in water and fall within these guidelines. Typical monomers used in emulsion polymerisation processes are the styrenics (149, 353), acrylics (141), methacrylics (309), vinyl acetate (164), vinyl chloride (363), acrylonitrile (152), butadiene (307), ethylene (114), as well as various speciahty (100) and functional monomers (332). 

---