General Purpose Adhesives

Adhesives. Poly(vinyl alcohol) is used as a component in a wide variety of general-purpose adhesives to bond ceUulosic materials, such as paper and paperboard, wood textiles, some metal foils, and porous ceramic surfaces, to each other. It is also an effective binder for pigments and other finely divided powders. Both fully and partially hydrolyzed grades are used. Sensitivity to water increases with decreasing degree of hydrolysis and the addition of plasticizer. Poly(vinyl alcohol) in many appHcations is employed as an additive to other polymer systems to improve the cohesive strength, film flexibiUty, moisture resistance, and other properties. It is incorporated into a wide variety of adhesives through its use as a protective coUoid in emulsion p olymerization. 

SBR adhesives are used in applications where low stress but high flexibility and resistance to shock are needed. If ageing is critical, SBR adhesives should not be used. SBR adhesives have relatively low surface energy and therefore can be used as general-purpose adhesive to join several substrates. 

One commercial adhesive is marketed with the following claims High Strength Adhesive Durable Bonding Fast Acting Bonds Metals, Rubber, Ceramics, Plastics, Glass, Wood, Veneers, Fabrics, Vinyl, Cardboard, Cork, Leather, Nylon, and Other Similar Surfaces. 1 How can one substance act as a general purpose adhesive with affinity for so many types of surfaces ... 

Amidoamines Reduced volatility Convenient mix ratios Good toughness Poor elevated-temperature performance Some incompatibly with certain epoxy resins General-purpose adhesives Construction adhesives Concrete bonding Toweling compounds... 

Two Component Adhesive Starting Formulation, General Purpose Adhesive, Air Products and Chemicals Company, Allentown, PA, 2001. 

The polysulfide additive provides excellent adhesion to concrete because of its chemical nature and low viscosity, resulting in good penetration. Table 11.16 describes a formulation for a flexible epoxy-polysulfide adhesive. This adhesive is claimed to provide excellent adhesion between new and old concrete surfaces. Table 11.17 describes several epoxy-polysulfide formulations for general-purpose adhesives. 

Components Tough, general-purpose adhesive Tough, general-purpose adhesive Concrete bonding adhesive... 

General-purpose adhesive good chemical resistance... 

Scotch-Weld 2214 3M Company 60 min at 121°C Aluminum-filled, general-purpose adhesive... 

Structural adhesives General-purpose adhesives Crack injecting systems Anchoring systems Grouts... 

General purpose adhesive Adhesion to wood, stone, bricks, metals, plastics, ceramics Various bonding applications... 

Depending upon the end-use, an epoxy adhesive can be classified further as a structural adhesive, general purpose adhesive or tile adhesive. 

Today, even in the most developed countries, natural adhesives dominate the market because they are less expensive than synthetic-based materials, and they perform the intended function. Natural rubber is still the most widely used base material in pressure-sensitive adhesives. The first such modern uses were flypaper to trap flying insects, and medical bandages and tapes. Because of restrictions on the use of pesticides in many countries, both natural rubber and sticky synthetic materials have returned full circle to one of their original uses in trapping rodents and other small mammals. Natural rubber solvent solution adhesives are widely used throughout the world as general-purpose adhesives. 

Uses Epoxy for floor topping and repair compds., general purpose adhesives, laminating binders, casting and encapsulation compds., solventless or high-solids/low-VOC coatings Properties Gardner 1 color dens. 9.56 Ib/gal vise. 2180 cps EPON Resin 58134 [Resolution Perf. Prods.)... 

Uses Polychloroprene for wire/cable, hose, gaskets, seals, tire sidewalls, molded/extruded goods, cellular prods., sealants, protective coatings, general-purpose adhesive cements... 

But often solvents must be used in adhesives in order to lower their viscosity so that product can be applied without the use of extensive force and so that the adhesive can flow into small openings in the substrate surface to promote mechanical adhesion by anchoring. The easiest formulating technique is to add solvent. This is simple and there is no need to develop new polymeric material. This is particularly true of polyurethane based adhesives which require either a special blending techniques or manufacture of the polymer with low viscosity polyols to reduce its viscosity. However, formulation of polyurethanes without solvents is technically possible as shown in patents for an automotive adhesive and a general purpose adhesive." In these areas additional research will bring dividends but the current effort lags behind the needs. 

In the two-part mixed versions the amount of hardener added to the monomer can vary between 5% and 50% depending on the formulation. These are suitable as general purpose adhesives capable of filling gaps up to 5 mm in thickness with a usable life of between 10 and 60 minutes. In the unmixed versions the hardener is applied as a thin film to one of the surfaces to be bonded. The monomer is then applied to the opposite surface, the parts immediately fitted together and held under contact pressure. The polymerisation starts instantaneously after the adhesive touches the hardener and requires about 15-20 minutes before the bonded joint can be handled. Although the overall performance is generally better than with the mixed versions, the gap which can be filled is limited to about 0.5 mm. 

The most suitable adhesive for general weldbond applications is modified-epoxy one-part paste type containing metal filler. Most adhesives used for weldbonding are arbitrarily selected from adhesives that were developed for other purposes, resulting in a compromise when used for weldbonding. Adhesives specifically developed for weldbonding should show improvements over general-purpose adhesives. ... 

Adhesive price is dependent on development costs and volume requirements. Adhesives that have been specifically designed to be resistant to adverse environments are more expensive than general-purpose adhesives. Adhesive prices range from pennies a pound for inorganic and animal-based systems to hundreds of dollars per pound for certain heat-resistant synthetic adhesives. Adhesives in film or powder form require more processing than liquid or paste types and are more expensive. 

Substrate General purpose adhesives (EtCA) Metal-bonding adhesives ... 

EN 15274 General purpose adhesives for structural assembly. Requirements and test methods. 

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