Solids adhesives

The test with the step loading shows that acoustic activity of the solid adhesive joints in the tested carbon plastic is quite low. The maximum on the endurance area was fixed at the predestructive moment. The last is evidence to the fact that the prevailing defect of the adhesive joints is starting its development at the loading level, which is close to the destruction point. 

Lee, I. and Wool, R.P, Thermodynamic analysis of polymer-solid adhesion Sticker and receptor group effects. J. Polym. Sci. Polym. Phys. Ed., 40(19), October (2002). 

A variety of applications exist for liquid, 100% solid adhesives, (An adhesive is considered 100% solid if there is no solvent in the adhesive.) Some of the largest uses include structural wood adhesives and adhesives used for the transportation industry, such as windshield adhesives and those used for bonding composite sidewalls of a recreational vehicle (RV). Structural wood adhesives are often made of a polymeric MDI with functionality of approximately 2.7 or higher. Rigid assemblies often utilize polymeric MDI, whereas flexible adhesive assemblies will more often utilize pure MDI, a solid waxy material that melts at around 37°C, or a modified MDI , i.e., MDI that has been modified to make it a liquid at room temperature. Prepolymers are made with ratios of anywhere from NCO/OH = 1.6 to 3.0 or higher. 

Fig. 10 relates the composite extraction index (see above) obtained in the low-shear aqueous test system for these Tween surfactants, and adhesion tensions measured against various solids. Adhesion tensions against platinum and bitumen saturated pyrophyllite are irregularly related to tar sand extraction, while the adhesion tension against a fresh pyrophyllite surface is linearly (inversely) related to tar sand extraction. This is the first linear correlation between a measurable property of a surfactant solution and tar sand extraction which we have been able to obtain, and there appears to be no such finding in the literature. Fig. 11 gives the relations between extraction of bitumen with the paddle mill, solvent-aqueous-surfactant extraction and adhesion tensions measured against platinum, bitumen saturated pyrophyllite and hydrated (48 hours in water) pyrophyllite. 

Plasters are solid adhesive (with cloth) preparation applied to the skin to protect, soothe and lessen pain e.g. Mustard plaster. Capsicum plaster. 

New insights into solid/solid adhesion have been provided by Chaudhury and Whitesides [12] who have directly studied the adhesion forces between various silicone surfaces. They analyzed the deformations occurring on contact of small... 

One effect of a lubricant is to reduce adhesion between the solids. Adhesion between solids is usually dominated by van der Waals forces. Hydrocarbons have a small Hamaker constant and their presence leads to a reduction in the adhesion and hence friction. Films of only a monomolecular thickness are sufficient to have a pronounced effect. This shows up when we measure friction between solids, which are coated with monomolecular layers (see example 11.1). In that case, friction can be as small as friction with plenty of lubricant. A monomolecular film affects significantly the frictional properties [495], At least with metals it can be shown that the number of microcontacts is not changed by the lubricant. Only the contact intensity is reduced. The reduced van der Waals attraction can thereby diminish the actual contact area. 

Dicyandiamide Latent cure Good elevated-temperature properties Good chemical resistance Good combination of tensile and peel strength Long elevated-temperature cure Insoluble in resin One-component adhesives Powder coatings Film and solid adhesives Laminates and other composites... 

Heat curing epoxy systems may consist of one or two components. The nomenclature is similar to that employed with the room temperature curing adhesives (e.g., resin component, curing agent component, 2Ksystem, etc.). Many heat curing epoxy adhesives systems are liquids or pastes. However, heat curing systems also can be processed into solid adhesive forms (e.g., powders and films). This chapter describes the paste and liquid formulations solid adhesive forms are considered separately in Chap. 13. 

Epoxy adhesives are most commonly used as liquids or pastes. However, certain types of epoxies can be employed in the form of a solid. The components in these adhesives are mixed and processed to a stage where the resulting adhesive product is in a solid but still fusible (uncrosslinked) state. When the applied solid adhesive is heated, it melts, flows, and wets the substrate. Additional heating time then causes the adhesive to cure completely into a strong, thermosetting structure. 

The main advantages of solid adhesives are that they are single-component (i.e., metering and mixing are not required) and that they can be applied uniformly to a substrate with... 

Other latent curing agents that are used in solid adhesives are dihydrazides and BF3-MEA complexes. These compositions are also stable at room temperature but cure when heated. Solid anhydrides can be used in one-component powder blends (e.g., 10 pph of trimellitic anhydride accelerated with 0.5 pph of 2-methylimidazole). Solid systems with aromatic diamines are prepared by comelting the solid epoxy with the amine. Typically 30 pph of curing agent is used.1... 

Knowledge of the surface dynamics of a solid has recently allowed significant progress in many academic and scientific fields adsorption (gas-solid interaction), wettability (liquid-solid), adhesion (solid-solid), and in applications catalysis [1,2], membrane [3,4], friction [5-8], blending [9,10],... 

Solid-solid Adhesion Solid suspension, adhesion, cohesion, corrosion, passivation, epitaxial growth, wear, friction, diffusion, thin films, delamination, creep, mechanical stability, durability, solid state devices, blend and alloy, charge transfer, nucleation and growth abrasion... 

These surface-anchored layers can be used as adhesion promoters to enhance elastomer-solid adhesive strength. We have shown that there is then an optimum surface density of surface anchored chains to do so. At high coverage of the surface, the layers lose their efficiency, a tendency which can be rationalized in terms of interdigitation between the elastomer and the surface chains. A full characterization of the different regimes of adhesion enhancement associated with the different regimes of interdigitation between the surface chains and the elastomer is a difficult experimental task, not fully accomplished to date. 

Figure 5.4. Interfaces lost or fonned during inunersional, adhesional and spreading wetting and during solid-solid adhesion.

The size of the contact angle depends on the magnitude of the liquid-solid adhesive force compared with that of the liquid-liquid cohesive force. Specifically, Young s equation (also called the Young and Dupre equation) indicates that... 

First-generation solventless polyurethane adhesives are one-component isocyanate terminated prepolymers formed by the reaction of MDI (4,4 methylene bis (phenyl isocyanate)), or other isocyanates with polyether and/ or polyester polyols. One-component 100% solids adhesives rely on moisture from the air or substrates or from induced moisture misting during the converting process, to cure the adhesive via an isocyanate/water reaction and subsequent polyurea-polyurethane polymer formation. Typically the high viscosity of the adhesive is such as to require adhesive delivery equipment and application rollers heated from 65-80 °C for use. They have a high level... 

The transformation of liquid monomers to solid adhesive involves an increase in molecular size and molecular weight through polymerization. The increase in molecular weight of the polymeric adhesive is responsible for the attainment of adequate mechanical properties, cohesive strength, impact strength, etc., and should, therefore, be allowed to proceed to the required levels during bond formation. 

Some examples of solid-solid adhesion processes are shown diagrammatically in Fig. 

Most thermoplastic foams can be solvent cemented. However, some solvent cements will collapse thermoplastic foams. The best way to determine if such a problem exists is to try it. In cases where the foam collapses due to softening of the foam cell walls it is desirable to use water-based adhesives based on SBR or polyvinyl acetate, or 100%-solids adhesives. In general, the relatively amorphous thermoplastics, such as the cellulosics, polycarbonate, and polystyrene are easier to solvent cement than the crystalline materials, but there are exceptions. 

Some solvent cements and solvent-containing adhesives, such as pressure-sensitive adhesives (PSAs), will collapse thermoplastic foams by dissolving the cell walls. In such cases water-based adhesives based on SBR or polyvinyl acetate, or 100%-solids adhesives are often used (1). 

Adhesive Nonmetal (working) material joining two or more adherends after being transferred from the liquid state into a solid adhesive layer. 

Heat-sealing adhesive A hot-melt adhesive applied to the adherends as solid adhesive layer, which melts under heat/pressure and joins the adherends after cooling. 

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