Polyacrylic adhesives

Tanamer [Cytec]. TM for sodium polyacrylate adhesive for use during the drying of leather. 

Given that the metal surface tension was the s lme in all cases, the thermodynamic work of adhesion depends on the interphase tension and on the adhesive surface tension. In this case (see Fig. 2.22) a correlation is seen between the thermodynamic work of adhesion and the adhesion strength. This correlation was determined earlier by Lipatov and Myshko by applying the modified equation of Dupre-Young [102]. Epoxy, polyester, polyurethane, and polyacrylate adhesives were used the type of the adhesive did not have a significant effect on the correlation dependence. 

Polyacrylics. Polyacrylic adhesives and sealants are formulated from functional acrylic monomers, which achieve excellent bonding upon polymerization.Alkyl esters of acrylic or methacrylic acids up to 80,000 molecular weight constitute the main bonds of acrylic sealants. 

Fig. 2. Influence of carboxyl content on Mylar-to-alu-minum bond strength of polyacrylate adhesives.

A range of acetoacetylated lesins has been intioduced (68,69). The acetoacetoxy functionahty can be cioss-linked with melamine—formaldehyde resins, isocyanates, polyacrylates, and polyamines. There is particular interest for possible corrosion protection on steel because the acetoacetoxy group can form coordination compounds (qv) with iron, perhaps enhancing the adhesion to steel surfaces (see Chelating agents). 

Thickeners can be added to increase the viscosity of the NR adhesives. Natural materials can be used such as casein or karaya gum, but currently synthetic polymers are used (methyl cellulose and derivatives, polyacrylates). 

Thickeners. Thickeners increase the viscosity of the polychloroprene latex adhesives. Amounts up to 1% of polyacrylates, methyl cellulose, alginates and polyurethane thickeners can be used. Particular attention should be paid to fluctuations in pH when thickener is added in the formulations. For low-pH (7-10) formulations, fumed silica or some silicates can be used. 

Standard-grade PSAs are usually made from styrene-butadiene rubber (SBR), natural rubber, or blends thereof in solution. In addition to rubbers, polyacrylates, polymethylacrylates, polyfvinyl ethers), polychloroprene, and polyisobutenes are often components of the system ([198], pp. 25-39). These are often modified with phenolic resins, or resins based on rosin esters, coumarones, or hydrocarbons. Phenolic resins improve temperature resistance, solvent resistance, and cohesive strength of PSA ([196], pp. 276-278). Antioxidants and tackifiers are also essential components. Sometimes the tackifier will be a lower molecular weight component of the high polymer system. The phenolic resins may be standard resoles, alkyl phenolics, or terpene-phenolic systems ([198], pp. 25-39 and 80-81). Pressure-sensitive dispersions are normally comprised of special acrylic ester copolymers with resin modifiers. The high polymer base used determines adhesive and cohesive properties of the PSA. 

The precise nature of the adhesion of the polyelectrolyte cements to untreated dental enamel and dentine has yet to be established. The earliest theory was due to Smith (1968) who speculated that the polyacrylate chains of the cement formed a chelate with calcium ions contained in the hydroxyapatite-like mineral in enamel and dentine. Beech (1973) considered this unhkely since it involved the formation of an eight-membered ring. Beech studied the interaction between PAA and hydroxyapatite, identified the formation of polyacrylate and so considered that adsorption was due to ionic attraction. 

The tacky polymeric microspheres that comprise the pressure-sensitive adhesive layers of repositionable notes are patented inventions. One such material (U.S. Patent 5,714,237) is prepared by a free-radical polymerization reaction of isooctyl acrylate (Fig. 14.3.1) in the presence of polyacrylic acid with a chain-... 

A product is only considered to be totally biodegradable if all its single components can be degraded naturally. Currently, pressure sensitive adhesives (PSA) are mostly based on non-biodegradable synthetic polymers such as polyacrylates, ethylene-vinyl acetate copolymers and styrene block copolymers [124]. Therefore there is a growing demand for the application of biodegradable PSAs on naturally degradable products like paper and cardboard. 

More recently, increasing research attention has focused upon the use of mucoadhe-sive delivery systems in which the biopharmaceutical is formulated with/encapsulated in molecules that interact with the intestinal mucosa membranes. The strategy is obviously to retain the drug at the absorbing surface for a prolonged period. Non-specific (charge-based) interactions can be achieved by the use of polyacrylic acid, whereas more biospecihc interactions are achieved by using selected lectins or bacterial adhesion proteins. Despite intensive efforts, however, the successful delivery of biopharmaceuticals via the oral route remains some way off. 

Though animal glue was used as an adhesive for more than 3000 years but its commercial manufacture started only in 1808. Later on starch, casein and rubber based adhesives also came into use. After 1940, several synthetic resin adhesives have been developed. Polyacrylates are used commercially. 

Another trend observed during the past decade was the coating of liposomes with mucoadhesive polymers. Liposomes are coated with chitosan, long-ehain polyvinyl alcohol, and polyacrylates bearing a cholesteryl group [90]. Chitosan-eoated liposomes showed superior adhesion properties to rat intestine in vitro than the other polymer-eoated liposomes. In vivo, chitosan-coated liposomes containing insulin substantially reduced blood glueose levels after oral administration in rats, whieh were sustained up to 12 hr after administration [90]. 

Acrylic acid and its salts are raw materials for an important range of esters, including methyl, ethyl, butyl, and 2-ethylhexyl acrylates. The acid and its esters are used in polyacrylic acid and salts (32%, including superabsorbent polymers, detergents, water treatment chemicals, and dispersants), surface coatings (18%), adhesives and sealants (15%), textiles and non-wovens (12%), plastic modifiers (5%), and paper coating (3%). 

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]. 

Prior to the use of the adhesives, the dentin surface is etched with a conditioning solution which is usually an aqueous acidic solution of citric acid-ferric chloride, phosphoric acid, or even polyacrylic acid [192]. These solutions tend to demineralize the dentin and expose the collagen (organic fibers in the dentin) [193], and thereby result in higher bond strengths. The effects of various pre-conditioning treatments on the bond strength of 4-META to dentin have been discussed [194]. 

Aluminium drinking carts. There are many patents [8] referring to the use of fluorozirconic acid (H2ZrF6)-based systems to treat the surface of aluminium cans to improve the corrosion resistance of the metal and the adhesion of the applied coatings. Typically, the zirconium fluoride will be used in conjunction with polyacrylic acid, presumably to form a complex in situ which acts as an adhesion promoter. Such surface treatment of aluminium is not restricted to zirconium fluorides, as ammonium zirconium carbonate displays similar properties in such application areas. 

Polycarbophil-based bioadhesive tablets of metronidazole were tested for adhesion on bovine submaxillary mucin [74]. In a more recent study, metronidazole tablets based on a mixture of modified starch-polyacrylic acid showed an increased potential for the treatment of bacterial vaginosis [75]. 

Three classes of PSAs used most widely in transdermal systems are polyisobutylene (PIB), polyacrylate, and polydimethylsiloxane (silicone). More recently, hydrophilic adhesive compositions, hydrogels composed of high-molecular-weight polyvinylpyrrolidon (PVP) and oligometric polyethylene oxide (PEO), have been shown to be compatible with a broad range of drugs and are used in several commercial products.60... 

A numerically controlled mill fabricated trenches and through holes at the ends of the trenches in a thin, colorless, polyacrylic acid plate [26], This thin plate was bonded to a more rigid, transparent polycarbonate base plate with U V-curing optical adhesive. The through holes in the plate were connected to holes in the base plate, thereby forming one conduit. The latter holes did not penetrate the base plate, but rather were connected to cross-type arranged borings. Thereby, fluid connections could be attached to the side of the base plate. 

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