Epoxy-phenolic adhesives, effects

FIGURE 15.3 The effect of 260°C aging in air and nitrogen on an epoxy-phenolic adhesive.10... 

TABLE 15.5 Effect of Several Chelating Agents on the Resistance of an Epoxy-Phenolic Adhesive to Thermal Aging13... 

Fig. 119. Effect of storage at elevated temperatures on room temperature strength of stainless steel lap shear joints with an epoxy-phenolic adhesive (Hidux 1197A, Ciba-Geigy) (adapted from Althof, 1966).

Fig. 120. Effect of elevated temperature on sustained load. Stainless steel adherends, epoxy-phenolic adhesive (Hidux 1197A). The lines are drawn as lower envelopes of the range of the data points to the same scale as Fig. 119 (adapted from Althof, 1%6).

FIGURE 7.1 The effect of temperature on the tensile shear strength of modified epoxy-phenolic compared to other hybrid adhesives (substrate is aluminum).4... 

Not only is low tensile shear strength noticed on moisture aging, but also the mode of failure changes from one of cohesion to adhesion. Table 7.6 shows the effect of humidity and water immersion on an epoxy-nylon adhesive compared to a nitrile-phenolic adhesive. Substrate primers have been used with epoxy-nylon adhesives to provide improved moisture... 

TABLE 7.6 Effect of Humidity and Water Immersion on the Tensile Shear Strength of Epoxy-Nylon and Nitrile-Phenolic Adhesives 10... 

Chem. Descrip. Aminopropyltriethoxysilane CAS 919-30-2 EINECS/ELINCS 213-048-4 Uses Adhesion promoter for solv., water-based, solventless, and powd. system coupling agent tor metal treatment resin additive in mineral-reinforced polyester resin improves chem. bonding of resins to inorg. surfaces pigment treatment effective as primer or additive, esp. in epoxy, phenolic, PU, vinyl plastisols and imide systems food pkg. adhe-siv6s... 

HMIS Health 3, Flammability 1, Reactivity 1 Uses Coupling agent for plastics effects immobilization of enzymes sizing of glass fibers for making laminates filler for thermosets, thermoplastics as primer or additive, esp. in epoxy, phenolic, PU, vinyl plas-tisols and imide systems in food-pkg. adhesives Regulatory FDA 21CFR 175.105... 

Structural adhesives are normally categorized or subdivided into subclasses based on the resin chemistries used in their formulation, which can be in the form of solids, liquids, pastes or films. The most important categories of structural adhesives are the thermoset cured adhesives based on phenolic, epoxy and polyurethane or acrylic resins and include phenolic adhesives. Epoxide adhesives, Toughened epoxide adhesives, Polyurethane adhesives, Acrylic adhesives and Toughened acrylic adhesives. Several of the categories can be further subdivided into both one- and two-component adhesives. The one-component structural adhesives, which can be liquids, pastes or solids (films), usually require the inclusion of added energy for activation or to effect cure in the... 

Cotter has reported the results of weathering conducted at three sites over a period of six years. All adhesives performed best at the desert site, although the epoxy/polyamide bonds were considered the least durable. At the hot, wet tropical site, the epoxy/polyamide bonds lost most of their strength after two years, in sharp contrast to the excellent strength retention of specimens bonded with novolac-epoxy, nitrile-phenolic, and vinyl-phenolic adhesives. It was also found that the combination of environmental exposure and stress was particularly harmful, the effects being more pronounced with certain adhesives. Thus stressed epoxy/polyamide bonds all failed after two years tropical exposure and stressed vinyl-phenolic bonds under the same conditions lost strength rapidly after two years and all specimens had failed after six years. The novolac-epoxy and nitrile-phenolic were less effected by stress, as were an epoxy-phenolic and a modified epoxy. 

Extensive information on the durability of bonded aluminum joints is available in the reviews of Minford. " Figure 4 illustrates some typical results, showing the effect of adhesive variation on joint durability for a marine exposure. Vinyl-phenolics and nitrile-phenolics have an excellent history of joint durability and rank among the most resistant to environmental deterioration. In spite of this, however, the current trend is to use epoxy-based adhesives, which provide easier processing and higher peel... 

Primers are often used to help ensure an adequate service life and, indeed, the presence, and the chemical type, of any primer may play a crucial role in ensuring a long service life for the adhesive joint. For example, it will be shown later that the use of organometallic primers may be extremely beneficial and many commercial corrosion-inhibiting primers have been developed for use with epoxy aerospace adhesives following the above comments, it is probably not just a coincidence that many of the latter types of primers contain phenolic-based constituents. Examples of the effect of substrate surface pretreatments on joint durability were shown in Figs 4.16 and 4.17 and Table 4.15 further examples are illustrated in Fig. 8.8. 

The advanced applications for nitrocellulose plastisol propellants require that they be integrally bonded to the motor case. Successful case bonding for the multiyear storage life of a rocket calls for special adhesives and liners which are completely compatible with these highly plasticized propellants. Best results have been obtained with a combination of an impervious rubber liner and a crosslinked adhesive system with a limited affinity for the plasticizers used in the propellants. Examples of effective liners are silica-filled butyl rubber and chlorinated synthetic rubber. Epoxy polyamides, isocyanate-crosslinked cellulose esters, and combinations of crosslinked phenol-formaldehyde and polyvinyl formal varnishes have proved to be effective adhesives between propellant and impervious liners. Pressure curing of the propellants helps... 

It is becoming apparent that wood components, especially lignin, are chemically modified by solvents during wood dissolution, and that the resulting wood tars or pastes become highly reactive. Attempts have therefore been made to prepare effective adhesives, moldable resins and other products from wood after dissolution in phenols or polyhydric alcohols. This review presents recent progress on wood dissolution, and on the preparation of epoxy and phenol resin adhesives from kraft lignin. 

In general, the elastomer must be prereacted (adducted) with the epoxy for the toughening effect to take place. Adducts reduce the likelihood of early phase separation and maintain the solubility of the elastomer in the uncured resin system. For CTBN the reaction is carried out at high temperatures (150 to 160°C) and usually in the presence of a catalyst, such as tris-dimethylamino phenol or piperidine. The resulting epoxy-CTBN adducts are available from several suppliers, and they can be easily formulated into epoxy adhesives. 

The degree of tensile strength improvement is often in the 50 to 100 percent range. The effect of various fillers and loading ratios on the strength properties of epoxy adhesive formulation is indicated in Fig. 9.9. The effect of different fillers loaded at a constant 100 pph is indicated in Table 9.12 for shear strength on phenolic laminate and aluminum substrates. 

FIGURE 15.17 Effect of adhesive on the durability of etched 6061-T6 aluminum alloy joints exposed to a marine environment. (1) Two-part epoxy, (2) one-part epoxy, (3) nitrile-phenolic, (4) vinyl-phenolic, (5) vinyl-phenolic.33... 

Additives used in formulations have the purpose of improving the flow of the enamel, to improve the thermo-mechanical properties like heat shock, or to give better adhesion of the cured film to the copper surface. Some of the additives have multiple effects. Because these effects are very specific to a given poly(ester-imide) resin and varnish formulation, the product classes are here only enumerated. Phenolics [112,113], epoxies [114,115], and silicones [116] are well known and some of them were claimed. Better understood is the effect of the phenol... 

Uses Filler, additive for plastics, coating, friction, refractory, ceramic, construction, elastomer, sealant, and adhesive applies., for nylon, phenolic molding compds., epoxy, polyester, PU/polyurea Featiffes Cost-effective functional filler surf, modifications can improve processing, bonding between resin and filler, mech. and phys. props., material handling and warehousing, etc. 

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