Typical Polymer Compositions

A variety of polymer compositions are used as binders in decorative and protective coating applications. By definition, emulsion polymers are based on vinyl monomers, but even with this restriction there are a number of different polymer classes which can be used for a given application. The choice of polymer system depends on many factors, which we will highlight below in the context of specific examples of coating apphcations. In this section we give an overview of the major emulsion polymer classes and discuss their general performance characteristics. 

Historically, styrene-butadiene copolymers were the first emulsion polymers to be used for coating apphcations. These polymers were based on technology developed for synthetic mbber production during WW II. Typical polymer compositions were 65 % styrene with 35 % butadiene. While paints based on styrene-butadiene emulsion polymers opened the door for the development of synthetic latex paints, their cost-performance profiles were not particularly competitive with the solvent borne coatings present at that time or with the other emulsion polymer technologies which would be developed later. They now occupy only a very small segment of the coatings market 

Most emulsion polymers used in coating appHcations are based on the general copolymer compositions outlined above. However, commercial polymers usually utilize small amounts of specialty monomers to provide added performance features desirable for specific appHcations. 

In the wet state, emulsion polymer coatings exist in the form of a densely crowded colloidal dispersion. Good colloidal stability (resistance to particle-particle aggrega-Hon processes) is required in order to provide long term storage stability and to de-Hver the intended performance features. 

Steric stabilization is based on attaching low molecular weight, water soluble polymers to the particle surface. This layer of soluble polymers on the parHcle surface provides an entropically based repulsive interacHon between parHcles, thus conferring addiHonal colloidal stability. Both coulombic and steric stabiHzaHon inhibit un- 

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The most important stmctural variables are again polymer composition, density, and ceU size and shape. Stmctural foams have relatively high densities (typically >300 kg/m ) and ceU stmctures similar to those in Figure 2d which are primarily comprised of holes in contrast to a pentagonal dodecahedron type of ceU stmcture in low density plastic foams. Since stmctural foams are generally not uniform in ceU stmcture, they exhibit considerable variation in properties with particle geometry (103). 

Conducting polymer composite materials are typical disordered structures consisting of randomly (or according to a certain law) arranged particles of a conducting filler that are submerged into a polymer medium. In this case the filler particles have macro-... 

Resin bead polymer composition Either acrylic resins or, more generally, styrene (vinylbenzene, VB) are cross-linked with typically 4 to 20% divinylbenzene (DVB) in a copolymer network or matrix. 

Table 2.3 shows a typical rubber composition. Some rubber components are amongst the most difficult compounds to analyse. For example, vulcanisation chemicals are changed by incorporation into the polymer... 

However, other polymer composite materials also popular in solid-phase synthesis, such as polyethylene or polypropylene tea bags , lanterns, crowns, or plugs, are generally less suitable for high-temperature reactions (>160 °C). Therefore, micro-wave irradiation is typically not a very suitable tool to speed up reactions that utilize these materials as either a solid support or as containment for the solid support. 

The design and development of a new product will often depend upon establishing a link between its chemical composition and its physical properties or performance. Typical examples are the development of alloys and of polymer composites. 

Another approach to exploit the properties of nanocarbons consists in integrating them in standard fiber-reinforced polymer composites (FRPC). The rationale behind this route is to form a hierarchical composite, with the nanocarbon playing a role at the nanoscale and the macroscopic fiber providing mainly mechanical reinforcement. This strategy typically aims to give FRPCs added functionality, improve their interlaminar properties and increase the fiber surface area. The first two properties are critical for the transport industry, for example, where the replacement of structural metallic... 

Most practical electrodes are a complex composite of powders composed of particles of the active material, a conductive diluent (usually carbon or metal powder), and a polymer binder to hold the mix together and bond the mix to a conductive current collector. Typically, a composite battery electrode has 30% porosity with a complex surface extending throughout the volume of the porous electrode. This yields a much greater surface area for reaction than the geometric area and lowers polarization. The pores of the electrode structures are filled with electrolyte. 

Hydroxy-terminated polyester (HTPS) is made from diethylene glycol and adipic acid, and hydroxy-terminated polyether (HTPE) is made from propylene glycol. Hydroxy-terminated polyacetylene (HTPA) is synthesized from butynediol and paraformaldehyde and is characterized by acetylenic triple bonds. The terminal OH groups of these polymers are cured with isophorone diisocyanate. Table 4.3 shows the chemical properties of typical polymers and prepolymers used in composite propellants and explosives.E4 All of these polymers are inert, but, with the exception of HTPB, contain relatively high oxygen contents in their molecular structures. 

Albert Einstein derived a simple equation for the viscosity of a solution of spherical particles, and from this result it is obvious that if we could make the polymer in small colloidal-sized balls, then the solution would be much less viscous. Also, if we could use surfactants to stabilize (e.g. by charging) the polymer particles in water, then there would be no need for organic solvents. Both these conditions are neatly obtained in the emulsion polymerization process, which is schematically explained in Figure 5.3. A polymer latex is produced by this process and can contain up to 50% polymer in the form of 0.1-0.5 im size spherical particles in water. A typical starting composition is ... 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

Although a majority of these composite thermistors are based upon carbon black as the conductive filler, it is difficult to control in terms of particle size, distribution, and morphology. One alternative is to use transition metal oxides such as TiO, VO2, and V2O3 as the filler. An advantage of using a ceramic material is that it is possible to easily control critical parameters such as particle size and shape. Typical polymer matrix materials include poly(methyl methacrylate) PMMA, epoxy, silicone elastomer, polyurethane, polycarbonate, and polystyrene. 

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