Elastomeric adhesive

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 for 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. 

In addition to PSAs, elastomers are used in the construction industry for mastic compounds. Neoprene and reclaimed rubber mastics are used to bond gypsum board and plywood flooring to wood framing members. The mastic systems cure by evaporation of solvent through the porous substrates. Elastomer-adhesive formulation is particularly complex because of the need for antioxidants and tackiflers.  

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Elastomeric adhesives Elastomeric copolymei Elastomeric fibers Elastomeric polyamide... 

The synthesis in 1928 of polychloroprene or Neoprene, which has found much use in high strength elastomeric adhesives. 

The aim of this chapter is to describe the micro-mechanical processes that occur close to an interface during adhesive or cohesive failure of polymers. Emphasis will be placed on both the nature of the processes that occur and the micromechanical models that have been proposed to describe these processes. The main concern will be processes that occur at size scales ranging from nanometres (molecular dimensions) to a few micrometres. Failure is most commonly controlled by mechanical process that occur within this size range as it is these small scale processes that apply stress on the chain and cause the chain scission or pull-out that is often the basic process of fracture. The situation for elastomeric adhesives on substrates such as skin, glassy polymers or steel is different and will not be considered here but is described in a chapter on tack . Multiphase materials, such as rubber-toughened or semi-crystalline polymers, will not be considered much here as they show a whole range of different micro-mechanical processes initiated by the modulus mismatch between the phases. 

Rubber base adhesives, also called elastomeric adhesives, are widely used in industrial and household applications. In fact, about one-third of the adhesives used in the World are made from natural or synthetic rubbers. Some of the elastomeric adhesive systems showing industrial importance in recent years are the following ... 

Some rubber base adhesives need vulcanization to produce adequate ultimate strength. The adhesion is mainly due to chemical interactions at the interface. Other rubber base adhesives (contact adhesives) do not necessarily need vulcanization but rather adequate formulation to produce adhesive joints, mainly with porous substrates. In this case, the mechanism of diffusion dominates their adhesion properties. Consequently, the properties of the elastomeric adhesives depend on both the variety of intrinsic properties in natural and synthetic elastomers, and the modifying additives which may be incorporated into the adhesive formulation (tackifiers, reinforcing resins, fillers, plasticizers, curing agents, etc.). 

The first elastomeric adhesive was prepared at the end of the 18th Century and consisted of naphtha solutions of natural rubber. This kind of adhesive is currently... 

The chemical nature and molecular weight of the rubber will greatly determine the properties of elastomeric adhesives. However, some common characteristics can be found in most of the rubber base adhesives. The elastomeric adhesives show the following specific features in assembly operations. 

The viscosity of elastomeric adhesives determines their method of application. Typically, solvent-borne rubber compounds require low viscosities for application. Thus, viscosities lower than 0.6 Pas for spray, curtain or dip applications are required, whereas for brush application viscosities lower than 5 Pa s are generally used. Roll- coating technology requires viscosities between 5 and 15 Pa s. 

Goodman, D.L. and Byrne, C.A., Phase-separated dual-cure elastomeric adhesive formulations and methods of using the same. US Patent 5,997,682. 

TEDLAR films are supplied with different surface characteristics. A (one side adherable) and B (both sides adherable) surfaces are used with adhesives for bonding to a wide variety of substrates. These surfaces can be bonded with a variety of adhesives, including acrylics, polyesters, epoxies, elastomeric adhesives, and pressure-sensitive mastics. The S surface has excellent antistick properties and is being used as a mold-release film for parts made from epoxies, phenolics, elastomers, and other polymeric materials.94... 

Lee (41, 42) offers a valuable contribution on the mechanism of reinforcement and especially on the role of adhesion and wetting in elastomeric adhesives, pressure-sensitive tapes, nonpigmented organic coatings, and composites such as resin-reinforced rubbers or thermoplastics. I am sure it will generate much discussion. Lee (43) presents a... 

In contact molding, the block, say 2" thick, can be attached to the inner mold, and joints between the blocks made with an elastomeric adhesive, and then the FRP laid up upon, and bonded to, the back of the block. Now when the molds are stripped, the liquid contact face will be the borosilicate block, which has a top surface operating temperature of 960°F. In these higher thermal ranges, the coefficient of thermal conductivity of the block ranges from 0.60 to 0.75. Thus, it is possible to operate a vessel so lined at, say, 600°F, while keeping the inner surface of the FRP unit at about 320°F. For greater thermal drop (cooler FRP), a thicker layer of block would be used. 

Dl-SEA 210 Silicone. [GE SOicones] Two-component silicone elastomeric adhesive. 

Adhesives that reduce and dissipate stresses consist of low-modulus elastomeric types. Low-stress adhesives are required in attaching large die, large substrates, and flex circuitry. Low-modulus elastomeric adhesives are also used to attach and fillet large components to dampen vibration and shock. 

Now, while many rubber polymers exhibit many of these properties, none of them exhibits all of them, nor equally well. Each polymer type has its own unique set of properties and characteristics, which allows for an expanding array of choices for assembly applications. Listed below are the major areas in which elastomeric adhesives provide an advantage over other polymer types. 

Ease of modification Most elastomeric adhesives can be readily modified in viscosity, tack, drying time (for solvent-based products), strength properties, heat resistance, aging characteristics and other properties to fit process and... 

W. F. Harrington, Elastomeric adhesives, in Engineered Materials Handbook, Vol. 3 Adhesives and Solvents (H. R. Brinson, chairman), ASM International, Materials Park, OH, 1990, p.l43. 

Chem. Descrip. Hydrophobic silica disp. in mineral oil Uses Defoamer for latex and aq. coatings, elastomeric adhesives Properties Liq. sp.gr. 0.91 vise. 1200 cps Troykyd USM PA230 [Troy]... 

Low-modulus adhesives, on the other hand, have low deflections, low bending stresses, and high radii of curvature. For example, silicones and other elastomeric adhesives have low deflections of approximately 0.01 pm and radii of curvature of over 125,000 mm. 

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