Pressure sensitive adhesives applications

Gelva [Solutia], TM for a family of acrylic multipolymer products designed for high-performance, pressure-sensitive adhesive applications where skin adhesion, high temperature and/or diffi-cult-to-adhere-to surface are involved. Provided for both solvent and water based grades. 

Produced by a solution polymerization process, this material exhibited an ordered molecular structure with the styrene monomer located at the ends of the butadiene monomer chain. In addition, other monomers such as isoprene, ethylene, butylene, and others, could be added to the polymer chain, which further modified basic properties. These materials possess a continuous rubber phase for resilience and toughness, and a discontinuous plastic phase for solubility and thermoplasticity. A variety of different grades are also available for this type of SBR, with differences in molecular weight, differences in the types of monomers used, differences in structural configuration, and differences in the ratio of endblock to midblock. Both emulsion and solution polymerized grades of SBR are available as solvent-based and water-based adhesives and sealants. Block copolymers are extensively used for hot melt formulations and both water-based and solvent-based pressure sensitive adhesive applications. Today, SBR elastomers are the most popular elastomers used for the manufacture of adhesives and sealants. 

Surface energy of epoxies can be reduced by addition of methacrylates or acrylates which allows production of films which can be used as release agents for pressure sensitive adhesive applications. 

These polymers have typically been used without tackifying resins or with quite low levels of tackifying resin. The rationale for this is that the desired properties can be built into an acrylic polymer by changes in monomer composition, ratios or final polymer molecular weight. However, literally hundreds of acrylic polymers would be required to fill all of the pressure-sensitive adhesive applications, making this a rather undesirable situation for the producers of acrylic polymers. A number of resins have been found to be compatible with acrylic polymers. The properties obtained with combinations of these resins with a number of acrylics exhibit desirable adhesive properties as well as lower cost. In all cases, an ion-tolerant resin emulsion was used to ensure compatibility. 

Mecham, S. Sentman, A. Sambasivam, M., Amphiphilic Silicone Copolymers for Pressure Sensitive Adhesive Applications. J.Appl. Polym. Sci. 2010,116, 3265-3270. 

Higher Tg acrylic polymers are used for bonding of ceramic tiles, lamination of aluminum foil or plastic films to paper and wood, and in the treatment of textiles. The lower Tg (tacky) versions of the polymer, where the acrylic component is secondary to the elastomeric-based adhesive component, are used in pressure-sensitive adhesive applications. 

Pressure-sensitive adhesives (PSAs) are typically used to hold objects together by bringing the surfaces into contact under pressure, applied briefly at room temperature. Natural rubber, styrenebutadiene (SBR), butadiene-acrylonitrile rubber, thermoplastic adhesives, polyacrylates, and silicones are the typical materials used for pressure-sensitive adhesive applications. These materials have viscous properties to provide flow while resisting excessive flow, partial elastic behavior to be able to carry some load, the ability to store energy to provide peel and tack, and the capability to dissipate energy during usage. Tack may be obtained by the use of resinous softeners such as pine tar or rosin esters, by the use of mineral fillers and various coal tar or petroleum derivatives. 

Polyvinyl ether OR R methyl, ethyl, or isobulyl These polymers are frequently used in pressure-sensitive adhesive applications, as in cellophane tapes and skin bandages. 

Acrylics are some of the most common and most versatile materials used in the PSA industry. Although the basic monomers and some of the acrylic polymers have been known for about a century, their commercial application as pressure sensitive adhesives did not happen until after the Second World War. 

Silicones are probably best known for their application as sealants and as release materials for pressure sensitive adhesives [107]. The silicone polymer combines an inorganic backbone made from silicon-oxygen bonds with organic substitution on the silicon atom. This repeating unit, shown below is called a siloxane. 

Because of their ease of use and their cost-effectiveness relative to other methods of assembly, pressure sensitive adhesives continue to penetrate all kinds of industrial applications. Some of the main reasons PSAs and PSA coated articles are prime candidates for industrial applications include the following ... 

Pressure sensitive adhesives and adhesive-coated articles have found a growing list of applications in the automotive, marine, airplane and appliance industries. The main uses are in assembly and decoration, but applications in the areas of... 

The film that is selected for the application mainly controls the properties these products deliver to the customer. However, in the case of optical applications where transmission of the light is needed, the choice of pressure sensitive adhesive and the quality of the application to the substrate become very critical. Even for the non-optical uses, the PSAs have to perform reliably under sometimes very demanding circumstances. 

Ulman, K.L. and Thomas, X., Silicone Pressure Sensitive adhesives for healthcare applications. In Advances in Pressure Sensitive Adhesive Technology-2. Satas Donatas Ed., Satas and Associates, Rhodes Island, 1995, pp. 133-157. 

The adhesives employed for in-line adhesive application are generally of two types (1) flexible, but non-pressure-sensitive adhesives based on blends of saturated stryenic block copolymers and wax and (2) pressure sensitives based... 

Pressure-sensitive adhesives (PSAs) based on acrylic, natural rubber and silicone are employed primarily for ease of application. To name Just a few applications, PSAs bond decals to surfaces, interior decorative surfaces to interior panels, interior trim pieces in place directly or hook and loop tape for the same purpose, structural shims in place during manufacturing and acoustic (sound deadening) materials to body skin interior surfaces. Tape products with pressure-sensitive adhesive on one or both surfaces are used for such functions as cargo compartment sealing, as a fluid barrier to prevent spills and leaks in the lavatories and... 

The section on chemistry of adhesives evolves from rubber-based adhesives to semi- structural and finally to structural adhesives. Everaerts and Clemens provide a thorough description of chemistry and applications of pressure sensitive adhesives and Kinning and Schneider describe an enabling technology for pressure... 

Aqueous, removable, pressure-sensitive adhesive compositions, useful for high-performance applications, comprise a mixture of a copolymer of alkyl (meth)acrylate and N-substituted (poly)amide of (meth)acrylic acid and a copolymer of alkyl (meth)acrylate and ethylenically unsaturated carboxylic acid, where at least one of the copolymers is an emulsion copolymer. Polyoxyalkyl-enes and phosphate esters may be used as surfactants [234]. 

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. 

Kinning, D. J. Schneider, H. M. Release Coatings for Pressure Sensitive Adhesives. In Surfaces, Chemistry Applications, Chaudhury, M., Pocius, A. V., Eds. Elsevier Amsterdam, 2002 Chapter 12, pp 535-571. 

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. 

Adhesive Transfer Processes. Many polymers, whether deliberately or accidentally, are adhesives, so that much of the adhesive industry can be regarded as a part of the mbber and plastics industry. However, there are several important material-transfer applications involving polymer products that are so critically dependent on controlled adhesion that they merit specific mention in that category. They include hot stamping foils, release coatings for pressure-sensitive adhesive products, photocopier materials, transfer coatings, and transfer printing of textiles. 

---