Thermoplastic Emulsions

These are commercially the most important class of vinyl and acrylic polymers for coatings, forming the basis of most decorative paints used today. 

One of the most common types of emulsion for decorative paint is based on vinyl acetate internally plasticised with about 20 parts of vinyl versatate. Di-butyl or di-octyl maleate or fumarate are also used as plasticising monomers for vinyl acetate, but butyl acrylate or 2-ethylhexyl acrylate are now preferred. Vinyl acetate homopolymers externally plasticised with di-butyl phthalate are still widely used. 

Styrene-acrylic copolymers have replaced vinyl versatate copolymers in some areas where improved properties are required such as hydrolysis resistance, but the highest performance coatings are now based on the more expensive full acrylic emulsions. 

In recent years, there has been a fast growth in the use of terpolymers based on vinyl acetate - ethylene - vinyl chloride. These terpolymers do not give quite as good performance properties as the acrylics, but ethylene and vinyl chloride are relatively inexpensive monomers. 

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Aqueous thermoplastic emulsions Fast air-dry/flow-temperature forced dry Film formation guidelines must be followed... 

These materials do not cross-link during cure and they can be melted without significant change in their properties. They are single-component systems that harden upon cooling from a melt state, or by evaporation of a solvent or water vehicle. Wood glues are thermoplastic emulsions that are common household items. They harden by evaporation of water from an emulsion. 

Aqueous thermoplastic emulsions n. Water based acrylic emulsions with noncros-slinked latex particles. 

More recently, a number of interstitially crosslinked coating materials have been prepared.These are blends in which a water-soluble or water-dispersible resin, capable of crosslinking, is blended with an ordinary thermoplastic emulsion. The main resins include aminoplast, phenol-formaldehyde, polyurethane, epoxy, and drying oils. Applications include sealants, adhesives, and architectural coatings. 

Another way to classify polymers results from the consideration of their typical applications. Typical classes are Compression molding compounds, injection molding compounds, semi-finished products, films, fibers, foams (urethane foam, styrofoam), adhesives (synthetic adhesives are based on elastomers, thermoplastics, emulsions, and thermosets. Examples of thermosetting adhesives are Epoxy, polyurethane, cyanoacrylate, acrylic polymers), coatings, membranes, ion exchangers, resins (polyester resin, epoxy resin, vinylether resin), thermosets (polymer material that irreversibly cures), elastomers (BR, silicon rubber). 

Aqueous Thermoplastic Emulsions n Water-based acrylic emulsions with noncrosslinked latex particles. 

Much smaller quantities of thermosetting emulsions are used compared with either thermosetting solution polymers or thermoplastic emulsions. This is because one of the big advantages of emulsion resins of a very high molecular weight is of much less importance for thermosetting systems, where molecular weights are increased by... 

A variety of thermoplastic emulsion polymers are used in decorative coating apphca-tions, with VA-BAs, EVAs, styrene acrylics, and acryhcs being most popular. VA-BAs, EVAs and styrene acrylics are commonly used for interior flat wall coatings, with the... 

The diversity of release products and the wide range of release problems make classification difficult. One approach is by product form, with subdivisions such as emulsions, films, powders, reactive or iaert sprays, reactive coatings, and so on. Another approach is by appHcation, eg, metal casting, mbber processiag, thermoplastic iajection mol ding, and food preparation and packagiag. 

The first five of these techniques involve deformation and this has to be followed by some setting operation which stabilises the new shape. In the case of polymer melt deformation this can be affected by cooling of thermoplastics and cross-linking of thermosetting plastics and similtir comments can apply to deformation in the rubbery state. Solution-cast film and fibre requires solvent evaporation (with also perhaps some chemical coagulation process). Latex suspensions can simply be dried as with emulsion paints or subjected to some... 

Poly(acrylic acid) is insoluble in its monomer but soluble in water. It does not become thermoplastic when heated. The sodium and ammonium salts have been used as emulsion-thickening agents, in particular for rubber latex. The polymer of methacrylic acid (Figure 15.13 (VI)) is similar in properties. 

Latexes are usually copolymer systems of two or more monomers, and their total solids content, including polymers, emulsifiers, stabilizers etc. is 40-50% by mass. Most commercially available polymer latexes are based on elastomeric and thermoplastic polymers which form continuous polymer films when dried [88]. The major types of latexes include styrene-butadiene rubber (SBR), ethylene vinyl acetate (EVA), polyacrylic ester (PAE) and epoxy resin (EP) which are available both as emulsions and redispersible powders. They are widely used for bridge deck overlays and patching, as adhesives, and integral waterproofers. A brief description of the main types in current use is as follows [87]. 

Solution (S-SBR) consists of styrene butadiene copolymers prepared in solution. A wide range of styrene-butadiene ratios and molecular structures is possible. Copolymers with no chemically detectable blocks of polystyrene constitute a distinct class of solution SBRs and are most like slyrcnc-buladicne copolymers made by emulsion processes. Solution SBRs with terminal blocks of polystyrene (S-B-S) have the properties of self-cured elastomers. They are processed like thermoplastics and do not require vulcanization. Lithium alkyls are used as the catalyst. 

POLYVINYLIDENE CHLORIDE. [CAS 9002-86-2J. A stereoregular, thermoplastic polymer is produced by the free-radical chain polymerization of vinylidene chloride (H>C=CCIi) using suspension or emulsion techniques. The monomer lias a bp of 31.6°C and was first synthesized in 1838 by Regnault. who dehydrochlorinated 1,1.2-trichloroethane which he obtained by the chlorination of ethylene. The copolymer product has been produced under various names, including Saran. As shown by the following equation, the product, in production since the late 1930s, is produced by a reaction similar to that used by Regnault nearly a century earlier ... 

RESINS (Acrylonitrile-Butadiene-Styrene). Commonly referred to as ABS resins, these materials are thermoplastic resins which are produced by grafting styrene and acrylonitrile onto a diene-rubber backbone. The usually preferred substrate is polybutadiene because of its low glass-transition temperature (approximately —80°C). Where ABS resin is prepared by suspension or mass polymerization methods, stereospedfic diene rubber made by solution polymerization is the preferred diene. Otherwise, the diene used is a high-gel or cross-linked latex made by a hot emulsion process. 

In the 1960s, anionic polymerized solutron SBR (SSBR) began to challenge emulsion SBR in the automotive tire market. Organolithium compounds allow control of the butadiene microstructure, not possible with ESBR. Because this type of chain polymerization takes place without a termination step, an easy synthesis of block polymers is available, whereby glassy (polystyrene) and rubbery (polybutadicnc) segments can be combined in the same molecule. These thermoplastic elastomers (TPE) have found use ill nontire applications. 

The effect of various plasticizers was studied for a number of plastisols prepared both from emulsion and suspension PVC 2>6,7,37 42 46 4% Judging from the published data 48), the most viscous plastisols are formed with mesamole, low-viscosity plastisols with dioctyladipate taken as a base, irrespectively of PVC type. Plastisol viscosity may be controlled by certain additives small smounts of certain solvents may lower plastisol viscosity by as much as an order of magnitude37,41>, the use of bentonites makes pastes more dense 40,48>. Thermoplastic polyethylene may also be used as a thickening agent6,42). 

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