Adhesive pressure application

For some applications, such as for repulpable type PSAs, it may be advantageous to incorporate high levels of acrylic acid because this makes the polymer more hydrophilic. At the same time, high levels of acid also improve the water-dispersibility of the adhesive, especially at higher pH where the acid groups are converted to the more water-soluble neutralized salt form. Since the high level of acid increases the of the resulting polymer, a non-tacky material results. To make the adhesive pressure sensitive, the polymer can be softened with water-dispersible or soluble plasticizers, such as polyethers [68]. 

Thermoplastic block copolymers were used for pressure-sensitive and hot-melt rubber adhesives as from the middle sixties. These adhesives found application in packaging, disposable diapers, labels and tapes, among other industrial markets. The formulation of these adhesives generally includes an elastomer (generally containing styrene endblocks and either isoprene, butadiene or ethylene-butylene midblocks) and a tackifier (mainly a rosin derivative or hydrocarbon resin). 

Pressure-sensitive adhesives Pressure-sensitive adhesions are actually viscous polymer melts at room temperature. The polymers must be applied at temperatures above their Tg to permit rapid flow. The adhesive is made to flow by application of pressure. When the pressure is removed, the viscosity of the polymer is sufficient to hold and adhere to the surface. Many tapes are of this type where the back is smooth and coated with a nonpolar coating so as not to bond with the sticky surface. The two adhering surfaces can be separated, but only with some difficulty. 

Benedek, L, Pressure-Sensitive Adhesives and Applications, 2nd ed., CRC Press, Boca Raton, FL (2004). 

One of the most popular uses of radiant curing is the advancement (viscosity increase) or crosslinking of pressure-sensitive adhesives. These applications have been satisfied mostly with acrylate-based adhesive systems. With epoxy-based adhesives, the main applications are electrical and electronic components, the bonding of large aerospace structures such as composites, and the bonding of transparent substrates such as glass and plastic. 

There are many applications for polymeric waterborne adhesives. These include packaging adhesives, pressure-sensitive tape, coatings for textiles, wood adhesives, and various industrial adhesives and coatings. The potential applications for waterborne epoxy adhesives are more limited due to their lack of tack and pressure-sensitive characteristics and the time it takes for the chemical reaction to complete cure. However, waterborne epoxy systems have found significant markets in niche areas. 

Hot-melt pressure-sensitive adhesives (spray application). 

Contact adhesives Adhesives solidifying to an adhesive layer after the evaporation of the solvent ( contact dryness ) by pressure application. 

It is possible to obtain a good bond between fluoropolymers themselves, without the use of adhesives, by application of heat and pressure. Pressure can help drive the molten pol5mier into the pores of the substrate. Bond strength is dependent on the mechanical interlocking that is achieved by the adhe-... 

In plastics, wear depends on adhesion and deformation of soft material. Frictional forces are proportional to velocity rather than load as in the case of metals. A number of additives can improve wear and slip properties. PTFE has lower friction coefficient than any other material. Additionally, its particles form a film on shearing surfaces thus decreasing friction. Its addition is very effective in high-pressure applications. Optimum additions are 20% in crystalline polymers and 15% in amorphous ones. Molybdenum disulfide is primarily used in PA compounds. It works as a nucleating agent, promoting increased crystallinity in PA, thus providing harder, more wear... 

Natural rubber adhesive, or latex, is used in self-seal applications, where it makes use of its unique ability to bond only to itself with pressure. Applications include selfseal envelopes, press-to-seal cases, and cold-seal candy wraps. Natural rubber latex is also used in adhesives for lamination of polyethylene film to paper, such as in multiwall hags. 

Stabilization of Carboxylated Styrene Butadiene (X-SBR) Latices Carboxylated SBR latices are used as adhesives in applications where durability and flexibility are desired. Some of the major uses for X-SBR latex are in tufted carpet backing, paper coatings, wall and vinyl floor tile adhesives, and pressure-sensitive adhesives. Typically, discoloration is the first measure of the degradation of an X-SBR latex. Discoloration of a dried latex film can often be related to a loss of the physical properties and subsequently, to inferior performance in an adhesive formulation. Figure 9 illustrates the effects of adding an effective antioxidant system to an X-SBR latex on the level of discoloration as a result of static oven aging at 150°C (300°F). The addition of AO-4 alone... 

Adhesive, pressure-sensitive—A viscoelastic material which, in solvent-free form, remains permanently tacky at room temperature. Such material will adhere instantaneously and tenaciously to most soUd surfaces with the application of very slight manual pressure. These adhesives are frequently used on tapes. An adhesive which, in the dry state, is aggressively and permanently tacky at room temperature and firmly adheres to a variety of dissimilar surfaces upon contact without the need for more than finger or hand pressure. 

Pressure-sensitive adhesives (PSAs)— Adhesive materials which bond to adherend surfaces at room temperature immediately as low pressure is applied. Adhesives which require only pressure application to effect permanent adhesion to an adherend. 

Resins based on para-substituted phenols can be either one-step or two-step, but they cannot cure to a thermoset state. In the manufacture of phenolic resins, smaller quantities of acetaldehyde and furfuraldehyde are used in addition to formaldehyde. Furthermore, resorcinol, bisphenol A, and p-alkylphenols are employed, in addition to phenol, when special properties are desired. Formaldehyde concentrations of 37-50 weight % in aqueous solutions are most commonly employed. The catalysts most frequently used are acids such as oxalic, hydrochloric, sulfuric, p-toluenesul-fonic, and phosphoric and bases such as sodium, calcium, and barium hydroxide. In the weakly acidic range metal carboxylates are employed. Thermoset phenolic resins are employed as structural adhesives for laminating and bonding applications. Para-alkyl-substituted resins are employed as tackifiers in contact adhesives, pressure-sensitive adhesives, and hot-melt adhesives. 

Coating/dispensing Brush, trowel Spraying, extrusion Roll application (manual or automatic) Hot melt equipment Stencil, dip coating Film adhesives Pressure sensitive adhesives Preformed adhesives and sealants (in solid form)... 

Adhesives Solution adhesives consist of a mixture of solid rubber and other components dissolved in a solvent. Several adhesive systems are used to produce pressure-sensitive adhesives. The applications of solid... 

Adhesive coating Ease of adhesive coating after surface treatment or adhesive modification Ease of postfabrication Smooth surface Regular cellular structure Wide range of mechanical properties Pressure-sensitive adhesive coated applications, tapes, strips, pad, joints and gaskets... 

The company s annual picnic kicked off the 50th celebration on the weekend of September 17, with more than 850 local Kraton employees, retirees and their families attending. Kraton also constructed an exhibition hall to showcase its latest technological advancements, including the recent commercialization of a new C5 tackifier reduction technology. Kraton s new SlBS-based compound enables customers to reduce the amount of tackier resins by 15-20% while achieving similar or better performance at similar system costs in hot-melt pressure-sensitive adhesive (PSA) applications. 

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