Solvents rubber-based adhesives

Variety of form. Rubber base adhesives can be supplied for assembly operations as solvent or water-borne dispersions, hot melts, precast films, extruded tapes or reinforced films. In addition solvent and water-borne dispersions can be supplied as single or two-components systems. 

For viscosity or sag control. When the rubber base adhesive is applied on a vertical surface, addition of a filler prevents the adhesive from running down the wall. In solvent-borne formulations, fumed silica can be used as anti-sag filler. In water-borne systems, clays impart yield stress and excellent sag control. 

The solvent plays an important role in the performance of rubber base adhesives. The solvent is the carrier for all components of the adhesive. Furthermore, the solvent controls the viscosity, open time, tack and adhesion of rubber base adhesives. 

Polystyrene Although polystyrene is usually bonded by solvent cementing, it can be bonded with vinyl acetate/vinyl chloride solution adhesives, acrylics, polyurethanes, unsaturated polyesters, epoxies, urea-formaldehyde, rubber-base adhesives, polyamide (Versamid-base), polymethylmethacrylate, and cyanoacrylates. The adhesives should be medium-to-heavy viscosity and room-temperature and contact-pressure curing. An excellent source is a Monsanto Company technical information bulletin which recommends particular commercial adhesives for bonding polystyrene to a number of different surfaces. Adhesives are recommended in the fast-, medium-, and slow-setting ranges (10). 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

Variety of forms Rubber-based adhesives can be supplied to the user in solvent or water-based formulations, as a solid hot melt or a soft tacky extrusion, as a tape (reinforced or not, single or double-sided), as a film, and even pre-applied to a surface for later solvent or heat activation. Products can be single or multiple component, depending on the application requirements. 

Variety of bonding methods The numerous forms and types of rubber-based adhesives and sealants also provide for numerous mechanisms for developing bonds to surfaces. Contact bond, pressure sensitive, wet bond, heat reactivation, and solvent reactivation are all feasible modes of product assembly with these products. 

Virtually all rubber materials, and plastic materials, can be made into an adhesive or sealant compound. This is because many elastomers begin as monomers dispersed in water or solvent and are polymerized in situ. Latex products can remain so, while solid elastomers that are extracted from either water or solvent systems can be solvated with an appropriate organic solvent system. In addition, most solid elastomers exhibit thermal flow characteristics which can make them suitable for hot-melt formulations. And since there are many different rubber polymer families, it stands to reason that there will be many different rubber-based adhesives to identify and describe. Some, however, have... 

Certain general categories are also listed, such as alloys, aromatic polymer, conductive, delayed-tack, elastomeric adhesives, anaerobic, film and tape adhesives, hot-melt adhesives, inorganic glues, microencapsulated adhesives, rubber-based adhesives, solvent-based systems, thermoplastic resin adhesives, thermosetting-resin adhesives, and water-based adhesives. 

Solvent solutions and latex cements require the removal of the solvent from the adhesive before bonding can take place. This is accomplished by simple or heat-assisted evaporation. Some of the stronger or more environmentally resistant rubber-based adhesives require an elevated-temperature cure. Only slight pressure is usually required with pressure-sensitive adhesives (PSAs) to obtain a satisfactory bond. These adhesives are permanently tacky and flow under pressure, thus they provide intimate contact with the adherend surface. 

Adhesives used to bond acetal homopolymer to itself and to other materials, such as aluminum, steel, natural rubber, neoprene rubber, and Buna rubber, include polyester with isocyanate curing agent, rubber-based adhesives, phenolics, epoxies, modified epoxies, and vinyls. Solvent cementing... 

Use of Solvent-based adhesives in seaming stems from the pioneering work of Charles Macintosh in the last century seam bonding with rubber solutions was a method used in the original waterproof coats carrying his name. Developments of the rubber-bonded seams are used in the manufacture of items such as life jackets and life rafts. The following (in cross-linked form) are commonly used Natural rubber-based adhesives, Poiychioroprene rubber adhesives, Poiyurethane and butyl rubber. 

Solvent-based dispersions such as polyvinyl acetate. Polyurethane, polyesters, polyethers, acrylic copolymers, Rubber-based adhesives with tackifiers and plasticizers. 

In solvent-borne rubber adhesives, a variety of solvents can be chosen to control drying rate, adjust viscosity and dissolve important ingredients. Resins can be added to improve tack, wetting properties, heat resistance, bond strength and oxidation resistance. The most common resins nsed in rubber-based adhesives are rosins, rosin esters, and terpene, coumarone-indene, hydrocarbon and phenobc resins. Plasticizers and softeners reduce hardness, enhance tack and decrease cost of rubber adhesive formulations. Paraffinic oils, phthalate esters and polybutenes are typical plasticizers. Fillers are not often added to rubber adhesive formulations because they reduce adhesion. However they are sometimes used because they decrease cost and increase solution viscosity. Carbon black and titanium dioxide are also used to provide colour to the adhesives. Clays, calcium carbonate and silicates are also common fillers in rubber adhesive formulations. For water-borne adhesives, typically protective colloid, preservative, defoamers, wetting agents and emulsifiers are included in the formulations. 

Natural rubber (NR) is characterized by high cohesive strength and high tack. For use in solution adhesives, NR must be masticated sufficiently to break down gel and reduce viscosity for dissolution in suitable solvents. When low gel content is achieved, viscosity-stabilized rubbers dissolved without the need for mastication. It is usual to form the rubber into a thin layer to present a large surface to the solvent for rapid swelling (see Natural rubber-based adhesives). 

Depending on the rubber, the solvent can either be petroleum hydrocarbon of differing boiling ranges, aromatic hydrocarbon - usually toluene - or oxygenated solvents snch as ketones or esters. If non-flammability is required, then chlorinated solvents are nsed. See also Rubber-based adhesives. 

For instance, the heads and nozzles which are used for paints are not suitable for adhesives, because the rheology of adhesives is different from that of paints. Generally speaking, atomization of adhesives is more difficult than paints, and solvent-based, rubber-based adhesives tend to dry fast and clog the nozzle if the adhesive is not properly formulated for spraying (refer to the ch ter Polychloroprene Adhesives ). 

The basic types of rubber-based adhesives used for nonstructural applications are shown in Table 7.27. These systems are generally supplied as solvent solutions, latex ce-... 

Formulation. Unlike the natural rubber pressure sensitive adhesives, acrylic adhesives are often supplied in a ready-to-use form. Natural rubber adhesives require time-consuming and costly mastication of the rubber followed by dissolving in solvent. In addition, they must be formulated with a tackifier resin and antioxidants, neither of which is required with an acrylic adhesive. The acrylic adhesives are known for their good UV and oxidative stability while the rubber-based adhesives, because of their chemical unsaturation, are poor in these properties. In general, tackifiers are not required with acrylic adhesives as tack can be designed into the polymer by the proper choice of... 

Automotive Industry. Tapes are used for decoration of automobile bodies, to secure body side molding, and for electrical harnesses, but by far the largest use is for masking of surfaces during painting. Because such masking tapes must resist solvents and baking cycle temperatures, as well as peel cleanly later, crosslinked rubber-based adhesives are widely used. 

Rubber-based solvent cements are adhesives made hy combining one or more rubbers or elastomers in a solvent. These solutions are further modified with additives to improve the tack or stickiness and the degree of peel strength, flexibility, and the viscosity, or body. Rubber-based adhesive is used in a wide variety of applications, such as contact adhesive from plastic laminates used for counter tops, cabinets, desks, and tables. Adhesive is used on pressure-sensitive tapes as floor tile adhesive and carpeting adhesive. Self-sealing envelopes and shipping containers use rubber cements. Solvent-based rubber adhesives have been the mainstay of the shoe and leather industry. 

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