Adhesive match

Figure 10. 1SS/SIMS data from adhesive matching areas to adherend shown in...

In optical applications, in addition to optical liber claddings, special optical adhesives matching refractive indexes of optical glass components based on fluorinated epoxyacrylates and epoxymethacrylates are used.29 Fluoroalkyl methacrylates are frequently incorporated as comonomers with siloxanyl methacrylates into contact lenses for the improvement of oxygen permeability.31... 

Table 7.6 Refractive indices (Rl) of piastics and commonly used adhesives. A join is invisible if the adhesive matches the Rl of the object 0.01. A consolidant or coating should match the Rl of a surface 0.06 to give optimum saturation ...

Chem. Descrip. Synthetic wax CAS 8002-74-2 EINECS/ELINCS 232-315-6 Uses Lubricant candles chewing gum dental wax explosives film pkg. firearms floor polish furniture polish hot-melt adhesives matches paints paper rubber food and food-contact applies. 

The metals initially considered as possible adherends included 750-T5 aluminum, iron-silicon-bronze, 440C stainless steel, ductile Niresist, cast-iron, SAE No. 52100 steel, and chrome-plated steel. Since the thermal expansion coefficients of most resinous adherends and adhesives are several times that of these metals, the most advantageous metal adhesive match would utilize those metals with the highest coefficient. This would indicate the use of the aluminum, bronze, or stainless steel. The elimination of these materials, in favor of 52100 steel, due to factors outside the scope of this report, heightened the problem of thermal stressing. The use of Teflon further emphasized the thermal stress problem. 

Diffusion Theory. The diffusion theory of adhesion is mosdy appHed to polymers. It assumes mutual solubiUty of the adherend and adhesive to form a tme iaterphase. The solubiUty parameter, the square root of the cohesive eaergy deasity of a material, provides a measure of the iatermolecular iateractioas occurring within the material. ThermodyaamicaHy, solutioas of two materials are most likely to occur whea the solubiUty parameter of oae material is equal to that of the other. Thus, the observatioa that "like dissolves like." Ia other words, the adhesioa betweea two polymeric materials, oae an adherend, the other an adhesive, is maximized when the solubiUty parameters of the two are matched ie, the best practical adhesion is obtained when there is mutual solubiUty between adhesive and adherend. The diffusion theory is not appHcable to substantially dissimilar materials, such as polymers on metals, and is normally not appHcable to adhesion between substantially dissimilar polymers. 

The polymeric encapsulating resin, modified by additives, must possess adequate mechanical strength, adhesion to package components, manufacturing and environmental chemical resistance, electrical resistance, GTE matching, as weU as thermal and moisture resistance in the use-temperature range. 

The excellent chemical resistance and physical properties of PVA resins have resulted in broad industrial use. The polymer is an excellent adhesive and possesses solvent-, oil-, and grease-resistant properties matched by few other polymers. Poly(vinyl alcohol) films exhibit high tensile strength, abrasion resistance, and oxygen barrier properties which, under dry conditions, are superior to those of any other known polymer. The polymer s low surface tension provides for excellent emulsification and protective coUoid properties. 

Solders should flow promptly and smoothly over the surfaces of the parts to be joined. This property depends on the surface tension, viscosity, and adhesive properties of the molten solder. Finally, the color of a solder should match that of the metal employed, and its physical properties should be at least as good as those of the metal, in order for the joint not to be a source of weakness (150). 

The adhesion promotion of an organic matrix to an inorganic substrate using a silane has been studied to model the structure of the created interphase [64-66]. The polymer/silane interphase is influenced by the solubility parameter of both the silane coupling agent and the polymer. More interdiffusion occurs when the solubility parameters of the polymer and the silane closely match together. It is believed that this model can be applied to silicone adhesive/solid substrate system. 

The morphology of a typical urethane adhesive was previously shown in Fig. 3. The continuous phase usually comprises the largest part of the adhesive, and the adhesion characteristics of the urethane are usually controlled by this phase. From a chemical standpoint, this continuous phase is usually comprised of the polyol and the small amount of isocyanate needed to react the polyol chain ends. A wide variety of polyols is commercially available. A few of the polyols most commonly used in urethane adhesives are shown in Table 2. As a first approximation, assuming a properly prepared bonding surface, it is wise to try to match the solubility parameters of the continuous phase with that of the substrate to be bonded. The adhesion properties of the urethane are controlled to a great extent by the continuous phase. Adhesion to medium polarity plastics, such as... 

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