Adhesive polymers water-based

The homopolymer of vinyl acetate is not used as an engineering polymer but for adhesives and water-based emulsion paints (vinyl acetate is used as a minor comonomer for the copolymerization of PVC/VAC). 

What of water-based adhesives We can apply some of the same principles and technology learned from solvent-applied adhesives to water-based systems. First, many of the polymers and elastomers available are the same (Table 2). Not only are these polymers available in latex form, but many are produced in latex form. The solid rubber used in solvent-based adhesives was derived from the latex, so one is actually eliminating a production step. Secondly, many of the resins the formulator has experience with and confidence in working with are available in dispersed form (Table 3). Some of these products have been available for a number of years and others are still in developmental stages. 

Certain general categories are also listed, such as alloys, aromatic polymer, conductive, delayed-tack, elastomeric adhesives, anaerobic, film and tape adhesives, hot-melt adhesives, inorganic glues, microencapsulated adhesives, rubber-based adhesives, solvent-based systems, thermoplastic resin adhesives, thermosetting-resin adhesives, and water-based adhesives. 

While the stain may be visible at the surface of the primer coating after drying, it is effectively locked into the film and does not lead to discoloration of the topcoat. Binders for stain blocking primers are usually based on relatively hydrophobic emulsion polymers with acrylic or styrene acrylic compositions. Primers are expected to have excellent adhesion, and water based primers are formulated to adhere to a variety of substrates including metal, wood, and chalky or aged re-paint surfaces. Since this level of performance may not be needed, or achievable, in many topcoat formulations, the use of specialized primers offers a flexible and cost effective way to meet the performance needs of many different coating apphcations with a limited number of optimized topcoat products. 

Emulsion Adhesives. The most widely used emulsion-based adhesive is that based upon poly(vinyl acetate)—poly(vinyl alcohol) copolymers formed by free-radical polymerization in an emulsion system. Poly(vinyl alcohol) is typically formed by hydrolysis of the poly(vinyl acetate). The properties of the emulsion are derived from the polymer employed in the polymerization as weU as from the system used to emulsify the polymer in water. The emulsion is stabilized by a combination of a surfactant plus a coUoid protection system. The protective coUoids are similar to those used paint (qv) to stabilize latex. For poly(vinyl acetate), the protective coUoids are isolated from natural gums and ceUulosic resins (carboxymethylceUulose or hydroxyethjdceUulose). The hydroHzed polymer may also be used. The physical properties of the poly(vinyl acetate) polymer can be modified by changing the co-monomer used in the polymerization. Any material which is free-radically active and participates in an emulsion polymerization can be employed. Plasticizers (qv), tackifiers, viscosity modifiers, solvents (added to coalesce the emulsion particles), fillers, humectants, and other materials are often added to the adhesive to meet specifications for the intended appHcation. Because the presence of foam in the bond line could decrease performance of the adhesion joint, agents that control the amount of air entrapped in an adhesive bond must be added. Biocides are also necessary many of the materials that are used to stabilize poly(vinyl acetate) emulsions are natural products. Poly(vinyl acetate) adhesives known as "white glue" or "carpenter s glue" are available under a number of different trade names. AppHcations are found mosdy in the area of adhesion to paper and wood (see Vinyl polymers). 

Inks. Refined kaolin is a common ingredient in a large variety of printing inks (qv). In addition to extending the more expensive polymers present, ka olin also contributes to improved color strength, limits the penetration of the ink into the paper, controls rheology, and improves adhesion. Kaolin for this appHcation must usually be as white as possible and free from oversize particles. Surface treated clays are used to improve compatibiHty with oil-based ink. Clays can also be an ingredient in the newer water-based or uv-cured inks. 

Vinyl polymers [polystyrene, PVC, polyethylene, polypropylene, poly(vinyl acetate), poly(vinyl alcohol), polyacrylonitrile] -1920 Packaging, tubing, household goods, records, carpets, toys, water based paint, adhesives, varnishes Phthalate esters, poly(vinyl alcohol) ... 

The benefits demonstrated from the preservative use of Bronopol alone and in combination with other preservatives have been realised in several other application fields, namely polymer dispersions, adhesives, paper coatings and water-based paints. By way of example, the results of a study in a water-based paint system are reported, where Bronopol is evaluated alone and in combination with 2,2-dibromodicyanobutane (DBDCB). 

To conclude this discussion on zirconium, it is appropriate to look at the adhesion promotion effects of various zirconium compounds in flexographic and gravure ink printed on corona discharge-treated polyolefins and polyester. Flexographic and gravure inks are basically a pigment (often titanium dioxide) suspended in a polymer (normally called the binder) dissolved in a solvent. Actual commercial ink formulations are rather more complicated. These inks are either water-based when acrylic polymers and co-polymers are typically the binders, or solvent-based (usually ethanol-ethyl acetate mixtures) when the binder is typically nitrocellulose or cellulose acetate propionate. 

Water-Based. In these adhesives, the polymers are in aqueous dispersions or solutions from which water evaporates to effect the transition in the case of dispersions, the particles coalesce to form a continuous film with solutions, the film is formed from polymer coming out of solution. 

The solids contents of these dispersions generally are of the order of 50% to 60%, occasionally even higher, so that one may deposit from a certain thickness of wet adhesive quite a thick dry film of polymer. Solvent-based adhesives generally have lower solids contents (20% to 30%), and since the shrinkage after drying of water-based dispersions also is lower such adhesives can be formulated to fill gaps between materials as well as to bond them. 

Many polymers have a limited life and are subject to aging processes even before they are used in production. To delay these aging processes to a usable time period, antioxidants, antihydrolysis agents, and stabilizers are added to adhesive formulations. Antifungal agents or biocides are used in many water-based adhesive systems. 

The ever increasing emphasis on reducing air pollution and on health considerations emphasized by OSHA has provided a strong impetus for adhesive manufacturers to develop water-based emulsion polymer systems to replace the organic solvent-based systems on which the industry was founded. This has been a difficult process. 

Components with improved mechanical properties can be produced by mixing the above processable polymers with other polymers. For example, we have mixed conducting polymer colloids with water based latex paints to form conductive, electroactive paints with excellent adhesion to a range of metals [132], Interestingly, the paint-metal adhesion was actually increased by addition of the conducting polymer colloid. 

JIS K 6806 1985 Water-based polymer-isocyanate adhesives for wood. JIS K 6860 1974 General recommended practices for atmospheric exposure of adhesive bonds. 

The most common polymer of a vinyl ester is poly(vinyl acetate), CAS 9003-20-7, with the formula [-CH2CH(OC(0)CH3)-]n. Other vinyl esters also are known, such as poly(vinyl butyrate), poly(vinyl benzoate) CAS 24991-32-0, and poly(vinyltrifluoroacetate), CAS 25748-85-0. Poly(vinyl acetate) is typically obtained from the monomer with radical initiators, either by emulsion or suspension polymerization. The polymer Is used in water-based emulsion paints, adhesives [22], gum base for chewing gum, etc. Also, poly(vinyl acetate) is used as a precursor for the preparation of other polymers such as poly(vinyl alcohol) or poly(vinyl acetals). Thermal decomposition of poly(vinyl acetate) starts at a relatively low temperature, around 200° C, some of the reports regarding its thermal decomposition being given in Table 6.5.8 [13]. The same table includes references for poly(vinyl butyrate) and poly(vinyl cinnamate), CAS 9050-06-0. 

Adhesives are nonmetaUic substances used to join two surfaces by means of surface adherence (adhesion) and inherent strength (cohesion), DIN 16920. This definition of adhesives does not cover water glass adhesives, adhesive ceramics, or adhesive mortars. The substances used as adhesives are polymers that go through a liquid phase at least once (reactive adhesives) or more than once (hotmelts, thermally activated adhesives). The liquid phase can also be achieved by dissolution in suitable solvents (nonreactive adhesives). In dispersion adhesives, the polymer molecules are dispersed (finely distributed) in a liquid - usually water - whereby the polymer molecules themselves are not dissolved. Fig. 6. These adhesives are also known as water-based or aqueous adhesives. It must be remembered that solvents are contained in these adhesives in addition to the water. Genuine aqueous adhesives contain less than 5% solvents in the liquid phase. The dispersions crnitain, in contrast to the solute adhesive molecules, additional substances, disposal of which requires specific additional measures. Since the dispersions represent stable systems in water, the water-resistance of such adhesives is reduced. Their thermal and water resistance can be increased by additional crosslinking (usually with isocyanates). 

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