Silicone-based pressure sensitive

Toddywala, R. D., K. Ulman, P. Walters, and Y. W. Chien. 1991. Effect of physicochemical properties of adhesive on the release, skin permeation and adhesiveness of adhesive-type transdermal drug delivery systems containing silicone-based pressure-sensitive adhesives. Int. J. Pharmaceut. 76 77-89. 

Sihcone products dominate the pressure-sensitive adhesive release paper market, but other materials such as Quilon (E.I. du Pont de Nemours Co., Inc.), a Werner-type chromium complex, stearato chromic chloride [12768-56-8] are also used. Various base papers are used, including polyethylene-coated kraft as well as polymer substrates such as polyethylene or polyester film. Sihcone coatings that cross-link to form a film and also bond to the cellulose are used in various forms, such as solvent and solventless dispersions and emulsions. Technical requirements for the coated papers include good release, no contamination of the adhesive being protected, no blocking in roUs, good solvent holdout with respect to adhesives appHed from solvent, and good thermal and dimensional stabiUty (see Silicon COMPOUNDS, silicones). 

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... 

Silicone release liners are used as a nonadhering surface to which adhesive materials, such as, for example, pressure-sensitive adhesives, can be laminated. UV curable release coatings are based on poly(dimethylsiloxane) oligomers functionalized with acrylate or epoxy groups and are mostly coated onto papers or thin films. 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

The primary mode of bonding for a pressure-sensitive adhesive is not chemical or mechanical but rather a polar attraction to the substrate. This always requires pressure to achieve sufficient wet-out onto the surface thereby providing adequate adhesion. The four main varieties of pressure-sensitive adhesives are derived from rubber-based, acrylic, modified acrylic and silicone formulations. Release liners are used to carry the sticky label and enable it to be printed. The release liners are normally paper, treated with a very thin silicone coating to allow the label to be peeled away easily without tearing. Some transfer of the silicone into the adhesive is inevitable. 

Devices are secured to the skin by use of a skin-compatible pressure-sensitive adhesive, usually based on silicones, acrylates or polyisobutylenes. These adhesives are evaluated by shear-testing and assessment of rheological parameters (Musolf 1987). Standard rheological tests include creep compliance (measurement of the ability of the adhesive to flow into... 

The backing material and release liner can be fabricated from a variety of materials including polyvinylchloride, polyethylene, polypropylene, ethylene-vinyl acetate and aluminium foil. The most important property of these materials is that they are impervious to both drug and formulation excipients. The most useful backing materials conform with the skin and provide a balanced resistance to transepidermal water loss, which will allow some hydration of the stratum corneum, yet maintain a healthy subpatch environment. The release liners are usually films or coated papers and must separate easily from the adhesive layer without lifting off any of the pressure-sensitive adhesive. Silicone release coatings are used with acrylate and rubber-based adhesive systems, and fluorocarbon coatings with silicone adhesives. 

The hydrosilylation reaction, leading to the formation of an alkylsilane by addition of a hydrosilane unit (Si-H) to a double bond, is widely used in the production of silicon polymers, paper release coatings and pressure-sensitive adhesives. Many homogeneous organometalhc complexes based on Co, Ni, Pd, Rh or Pt have been used to catalyze this reaction, but strong evidence has proved that the really active species were metal colloids [95-97]. Moreover, it has been demonstrated that Pt colloids were the most effective catalysts for SiH addition to terminal olefins (98). However, Lewis et al. [99] have reported Rh colloids-catalyzed hydrosilylation (Scheme 11.16). The particles were prepared by the reduction of rhodium chloride by the silane reagents. The authors have shown that Rh colloids present an interesting activity in the addition of di- and trihydrides to olefins, compared to platinum colloids. 

Pressure-sensitive adhesives are applied from a liquid base, usually as hot-melts, and retain tack when they are cool and dry. To keep pressure-sensitive labels and other components from sticking to something before they are supposed to, they generally remain on a carrier web until they are ready to be applied. The carrier web is coated with a material that provides easy release, usually a silicone. 

Silicone adhesives were introduced commercially in 1944 [5, p. 213]. In 1960 the silicone sealants were introduced to the construction industry [11, p. 86]. Silicones are useful at both high and low temperatures and are available today as solvent-based moisture-curing adhesives, one-part moisture-curing adhesives and sealants, two-part curing adhesives and sealants, and pressure-sensitive adhesives. 

Two other classes of silicones deserve mention. These are the water-based silicones that are used in sealant and coating applications and the silicone pressure-sensitive adhesives. Water-based silicones can be prepared by anionic polymerization of siloxanes in water using a surface-active catalyst such as dodecylbenzenesulfonic acid [4]. The resulting emulsion can then be cross-linked in several ways, including the use of alkoxysilane copolymerization or tin catalysts in conjunction with colloidal silica. The result is essentially an emulsion of cured PDMS in water. Various fillers and other components are added, resulting in a sealant composition. Upon evaporation of water. 

Chem. Descrip. Water-based two-component silicone o/w emulsion Uses Release coating for general-purpose pressure-sensitive adhesive release applies., providing low release from films and papers of varying porosity, and suitable for food contact in resinous/polymeric food-contact coatings... 

Solid PIBs are used in plasticized formulations. In the drag containing adhesive of transdermal patch, 10-40 wt% plasticizer (mineral oil, silicone oil, octyl palmitate, etc.) is added to plasticize material and impart hydrophobic properties. Petrolatum or mineral oil was used in adhesive skin barrier which is a pressure sensitive adhesive based on... 

The chemistry of silicone resins and siloxane gums used to prepare silicone pressure sensitive adhesives is briefly reviewed. The thermal, dynamic mechanical and X-ray scattering properties of the silicone adhesives is presented. A specific morphological model for the silicone pressure sensitive adhesives is proposed based on the characterization data. The results for adhesives prepared from polydimethyl siloxane gums is compared to adhesive prepared from polydimethyl-co-diphenyl siloxane gums. 

Adhesives as materials can be classified in a number of ways such as chemical structure or functionality. In this book, adhesives have been classified into two main classes natural and synthetic. The natural group includes animal glue, casein- and protein-based adhesives, and natural rubber adhesives. The synthetic group has been further divided into two main groups industrial and special compounds. Industrial compounds include acrylics, epoxies, silicones, etc. An example of the specialty group is pressure-sensitive adhesives. 

Silicone polymeric materials are used in a variety of forms such as pure fluids, emulsions, solvent-based formulations, resins, elastomers and so on. They are formulated in numerous products for various applications involving different processes across many different industries. Some of these products where adhesion plays a major role are adhesives, coatings, encapsulants, hair conditioners. Pressure-sensitive adhesives, mould Release agents. Sealants, skin creams and so on. 

Most pressure-sensitive adhesives are made from formulations based on elastomer (natural, butyl, nitrile, and styrene butadiene thermoplastic), acrylate, or silicone resins. 

The results are reported of an investigation into the stability, in-vitro drug delivery and adhesive properties of drug-in-adhesive transdermal drug delivery systems. These systems are composed of a flexible backing film, a fluoropolymer release liner and active adhesives, which vary in their monomeric compositions and functionalities. The adhesives are composed of an acrylic pressure-sensitive adhesive, an amine-compatible silicone pressure-sensitive adhesive and methylphenidate base, as the drug. 4 refs. 

The surface applications of silicone products, particularly those based on polydimethylsiloxane (PDMS), are many and varied (7). Familiar examples include release liners for pressure-sensitive adhesives (PSAs), antifoaming agents, and water-repellent treatments for a wide variety of substrates. This broad diversity of application is a direct consequence of the low surface energy of PDMS which is lower than most other polymers except for those based on aliphatic fluorocarbon moieties. Despite the commercial importance of this aspect of the properties of polydimethylsiloxane, there is no fully satisfactory contact angle characterization of PDMS yet available. There is no lack of potential candidates part of the difficulty in identifying a definitive study lies in the breadth of these diverse wetting... 

These adhesives consist of a polymerizable liquid matrix and large volume fractions -of electrically insulating thermally conductive filler. Typical matrix materials are epoxies, silicones, urethanes, and acrylates, although solvent-based systems, hot-melt adhesives, and pressure-sensitive adhesive tapes are also available. Aluminum oxide, boron nitride, zinc oxide, and increasingly aluminum nitride are used as fillers for these types of adhesives. The filler loading can be as high as 70 - 80 wt %, and the fillers raise the thermal conductivity of the base matrix from 0.17-0.3 up to about... 

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