Emulsion glues

Emulsion glues (e.g., the poly(vinyl acetate) based white and yellow or carpenter s glues) harden by a variation on drying that involves coa-... 

Chem. Descrip. Ammine adduct with enzyme blocking agent Uses Preservative for paints, adhesives, polymer emulsions, glues, joint cements, and dry-mix prods. 

Bonds with higher water resistance can be achieved by using special blends or two-component emulsion glues. The second component may be a diisocyanate or particularly an inorganic salt (usually, aluminum nitrate). These hardeners, added in a quantity of at least 5 %, improve the moisture resistance of the joint. However, their addition limits the pot life. 

In industries that are bonding plasticized materials, there are some specific tests to measure for instance peel strength before and after accelerated aging test. The A and S suppliers, who know the raw materials included in their formulations, can tell quickly whether a given adhesive should be sensitive or not to oils, greases and plasticizers. Some adhesives are sensitive to oils (vinyl emulsion glues), some are not (epoxies, anaerobics, etc.). 

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). 

Poly(viayl acetate) emulsions or hot-melt adhesives are typically used to form the manufacturer s or glue lap joiat of the box. The main criteria for the adhesive is that it provide a strong and tough final bond and that it set up quickly enough to allow fast box production speeds. Production rates ia excess of 240 boxes per minute are not uncommon ia the iadustry. 

Poly(vinyl acetate) emulsions are excellent bases for water-resistant paper adhesives destined for use in manufacturing bags, tubes, and cartons. Glue-lap adhesives, which require moderate-to-high resistance to water, exemplify this type. When routine water resistance is required, a homopolymer vinyl acetate emulsion containing a ceUulosic protective coUoid is effective for most purposes. Next effective are emulsions containing fuUy hydrolyzed poly(vinyl alcohol) as a protective coUoid, foUowed by those containing partiaUy hydrolyzed poly(vinyl acetate). 

Rubber-based adhesives provide softness and good low temperature flexibility (see Table 8). These properties make them the primary choice for the hinge application, which are two thin glue beads applied to the sides of the book block adjacent to the spine. These adhesive beads allow the book to open with the cover and help to protect the spine glue from stresses. Hinge glues have low if any wax, and are pressure sensitive. When used for the spine application, rubber-based adhesives require a water-based emulsion primer due to their short open time and thus low penetration of paper substrates. 

In addition to the above, there are emulsion and suspension stabilizers that act as protective colloids and in some cases as thickeners gums (such as acacia and traga canth), alginates, starch and starch derivatives, casein, glue, egg albumin, methyl cellulose, hydrated Mg and Al silicates, etc Refs Same as in previous item... 

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(vmyl acetate). This is also known as white glue. ... 

Collagen and gelatin are of commercial importance. As insoluble collagen, this material may be cross-linked further by tanning and thus converted to leather. The soluble gelatins are used in the manufacture of foodstuffs, film emulsions, and glue. 

While unaffected by water, styrofoam is dissolved by many organic solvents and is unsuitable for high-temperature applications because its heat-distortion temperature is around 77°C. Molded styrofoam objects are produced commercially from expandable polystyrene beads, but this process does not appear attractive for laboratory applications because polyurethane foams are much easier to foam in place. However, extruded polystyrene foam is available in slabs and boards which may be sawed, carved, or sanded into desired shapes and may be cemented. It is generally undesirable to join expanded polystyrene parts with cements that contain solvents which will dissolve the plastic and thus cause collapse of the cellular structure. This excludes from use a large number of cements which contain volatile aromatic hydrocarbons, ketones, or esters. Some suitable cements are room-temperature-vulcanizing silicone rubber (see below) and solvent-free epoxy cements. When a strong bond is not necessary, polyvinyl-acetate emulsion (Elmer s Glue-All) will work. 

A sol is similar to a gel however, the mixture will flow, for example emulsion paint, or PVA glue. 

The major synthetic adhesives used for bonding wood include urea, phenol, and melamine formaldehyde resorcinol formaldehyde, phenol resorcinol, and polyvinyl acetate emulsions. More recently one-component, moisture cured polyurethane adhesives have become popular for bonding wood. Natural adhesives such as casein and animal glues are also often used for general-purpose wood bonding. Epoxies have been used for certain specialized wood joining applications such as when wood is bonded to metal substrates. 

Gelatin is used in foods, usually as a stabilizer or thickener. It is made into capsules for medicines, in glues and binders, in cosmetics, as sizing in paper, and in photographic emulsions. 

Animal and starch glues, especially because of their low color and ease of application on complex joint surfaces, were the adhesives of choice in the furniture and cabinet industries from colonial days until the advent of synthetic emulsion adhesives after World War II. Service conditions were limited to dry interior applications, of course. Leaving a chair out in the rain meant dismantling and regluing. 

In general, these groups of cellulose ethers have been used for their innate adhesive properties and to provide thickening to adhesive formulations. They are used for plywood adhesives, industrial adhesives, wallpaper paste, library paste, and latex adhesives. For example, methylcellulose is used in some adhesives as an additive to control viscosity, especially in the heat-cure phenol-formaldehyde glues and other hot-pressing adhesives. Hydroxyethylcellulose is used as an ingredient in polyvinyl acetate emulsions, where it acts as a thickener and protective colloid. 

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