Initial tack

High initial tack. The adequate choice of butyl or PIB provides excellent building tack (ability to produce quick adhesion by applying low pressure). 

This adhesive is a resin/solvent adhesive material compounded to supply satisfactory initial tack. The solvent system has been carefully selected for somewhat rapid evaporation, thereby requiring minimum temperature and ventilation. Useful in textiles and paper board industries. 

Resoles based on 4-terf-octy[ iesi(A react with alkaline-earth metal hydroxides to yield metal resinates. The resinate is combined with natural or synthetic mbber to produce an adhesive. The 4-/ l -octylphenol-based resin gives the adhesive its initial tack which holds the two surfaces undergoing bonding together while the other components of the adhesive undergo final curing. 

High initial tack Even without tackifying resin, the inherent tack of certain grades provides for excellent contact bond and pressure sensitive adhesives. 

Polychloroprene latex. Anionic or non-ionic latices can be used. The polymer determines the initial tack and open time, the bond-strength development and hot bond strength, the application properties and the adhesive viscosity. Anionic latices are stabilized with rosin soaps. Carboxylated polychloroprene latex is stabilized with polyvinyl alcohol and provides better freeze-thaw stability than the anionic types [78]. 

In the empirical world of tack experts, many professional terms are employed, like green strength (as initial tack is sometimes called), which relate to the resistance to separation before the adhesive has had a chance to vulcanize or crosslink. This characteristic may also be called quick tack or aggressive tack . It may be one of the most important properties in determining the suitability of an adhesive, such as that placed on a pressure-sensitive tape, for a certain application. Associated with tack is dry tack , which is a property of certain adhesives to stick to one another even though they seem to be dry to the touch. Autohesive tack (or autohesion) is the dry tack between materials having similar chemical compositions. Tack range is the time that an adhesive will remain in a tacky condition. 

Although of medium-to-high cost and of low initial tack, so as to need addition of tackifiers, NBR has a number of properties needed in specific service environments. Its temperature resistance is good if cured, NBR can easily be used at 150-175°C. Similarly, ageing properties, when compounded with adequate antioxidants, are excellent. 

Tackifier n. A substance (e.g., rosin ester) that is added to synthetic resins or elastomeric adhesives to improve the initial tack and extend the tack range of the deposited adhesive film. 

Tack enables an adhesive to form an immediate bond between contacting surfaces when they are brought together. It permits the alignment of an assembly and prevents the adherends from separating before the adhesive sets. Tack is differentiated into two types (1) wet tack, also called grab or initial tack, is the tack of an adhesive before the liquid carrier, ie, organic solvent or water, has fully evaporated (2) dry tack, also called residual tack or pressure sensitivity. 

Other Theories. In addition to these theories, some special cases are discussed in the literature. They include adhesion by primary valence forces, for example, in the bonding of metals [8], [23], and so-called liquid adhesion. In the latter, a thin film of a liquid of extremely high viscosity produces adhesion through a process in which separation of adherent and substrate results in a flow in the narrow gap which is only possible by overcoming considerable resistance. Liquid adhesion is particularly assumed in pressure-sensitive bonding [16] and in the initial tack of a liquid adhesive. 

Lamination of Paper and Board. Adhesives based on starch, dextrin, glutin and poly(vinyl alcohol), and also emulsion adhesives, mainly polyfvinyl acetate), are used for the lamination of paper and board. Only when high initial tack and a lay-flat effect are required are hot glues based on glutin still in use. Starch-based adhesives modified with silicate, casein-stabilized copolymer dispersions, and rubber latices are used in the lamination of paper to aluminum foils. Modified polyacrylate solutions and reactive polyurethane adhesives are used mainly for paper-to-plastic lamination. 

Laminating Adhesives. Aqueous adhesives based on cellulose or poly(vinyl alcohol) for the ply lamination of tissue papers must give clean machinability, good initial tack, and reliable bonding strength of the tissue laminates. 

Linoleum Adhesives. Linoleum generally is laid with waterborne adhesives based on acrylic emulsions or SBR latex. They contain higher amounts of inert inorganic fillers, and natural and/or synthetic resin is used to accelerate initial tack. Linoleum adhesives have to set rapidly to avoid expansion or shrinkage of the covering. Two-component adhesives consisting of one polymer dispersion and a second cement preparation are available to adhere linoleum to nonabsorbent substrates. 

Adhesives for Textile Floor Covering. The composition of waterborne adhesives for bonding wall-to-wall carpets is similar to that of linoleum adhesives. High initial tack (wet tack) and a resistance against carpet cleaners is required. Previously used solutions of poly(vinyl ethers) and rosin in mixtures of highly volatile solvents are still used for carpets that are extremely sensitive to water. 

Manufacturers Comments Natural resin dispersion adhesive, solvent free. Water-based acrylic dispersion. Flexible with good initial tack. 

Materials Systems of Curing or Setting Methods of Application Application Temperature °F Resistance to Oils and Greases Resistance to Water Resistance to Weathering Resistance to Acids, Alkalies, Chemicals Initial Tack or Wet Strength Cohesive Strength (Dry) Porous to Porous Porous to Non-porous Non-porous to Non-porous... 

Adhesives should be applied only in a thin film, and care must be taken to avoid large deposits occurring. Initial tack is usually sufficient to hold the areas together but frequently the maximum bond strength can take up to 24 hours to develop. There are a number of methods of application, and for each component a suitable and appropriate method is available. The main methods that can be recommended are as follows. 

Their high initial tack upon irradiation, enables immediate further processing,... 

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