Phenolics, modified epoxy-phenolic

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... 

Vinyl-phenolic Nitrile-phenolic Vinyl-phenolic Neoprene-phenolic Nylon-phenolic Modified epoxy Nitrile-phenolic Epoxy... 

Phenolic Adhesives recommended are neoprene and urethane elastomer, epoxy and modified epoxy, phenolic-polyvinyl butyral, nitrile-phenolic, polyester, cyanoacrylates, polyurethanes, resorcinols, modified acrylics, polyvinyl acetate, and urea-formaldehyde (1). 

Modified epoxy - phenolic -glass fiber (heat resistant 5 x 10 epoxy)... 

In this Institute, there are approximately 200 research personnel and one fourth of them are working on adhesives in two laboratories, one pilot-plant, one testing group and one adhesive-film manufacturing and testing facility. Their research and development broadly covered structural adhesives, strain gauge adhesives, wood adhesives, second-generation acrylics, anaerobic adhesives and composite binders. Their products varied from J-01 to J-53. There were at least thirty different kinds of adhesive and sealant, for example, nitrile-phenolics, modified epoxies, acrylics and epoxy-phenolics. 

The primary intent of this article is to review the status of experimental and newly developed high temperature organic adhesives with particular attention to aerospace materials. Detailed information on the synthesis of various polymers or bonding conditions can be obtained in the references cited. Several high temperature adhesives are commercially available, and information on these systems can be obtained from the major adhesive suppliers. For aerospace use, these consist primarily of modified epoxy phenolics, toughened bismaleimides, addition and condensation polyimides. 

In addition to electrical uses, epoxy casting resins are utilized in the manufacture of tools, ie, contact and match molds, stretch blocks, vacuum-forrning tools, and foundry patterns, as weU as bench tops and kitchen sinks. Systems consist of a gel-coat formulation designed to form a thin coating over the pattern which provides a perfect reproduction of the pattern detail. This is backed by a heavily filled epoxy system which also incorporates fiber reinforcements to give the tool its strength. For moderate temperature service, a Hquid bisphenol A epoxy resin with an aHphatic amine is used. For higher temperature service, a modified system based on an epoxy phenol novolak and an aromatic diamine hardener may be used. 

The alkyd resins are of value because of their comparatively low cost, durability, flexibility, gloss retention and reasonable heat resistance. Alkyd resins modified with rosin, phenolic resin, epoxy resins and monomers such as styrene are of current commercial importance. 

Again, as in many other fields covered in the book, modified epoxies are the most studied systems (toughened epoxies for adhesive coatings and composites). But also rubber-modified phenolics and low-profile unsaturated polyesters for sheet and bulk molding compounds have been extensively studied. 

Alumina trihydrate Available in various particle-size grades and in surface-treated grades Polyesters, phenolics, and epoxies. Also polypropylene and ethylene/rubber compounds Albemarle-Martinswerk, Alcan Chemicals, Alcoa, Aluchem, Amspec Chemical, DuPont Polymer Modifiers, J.M. Huber, Nabaltec... 

A significant advantage of tape and film adhesives is the greater toughness that is available compared to other adhesive types. This is primarily due to the ease with which resinous modifiers can be added to the formulation via solvent solution. Thus, hybrid epoxy adhesives such as epoxy-nylon, epoxy-phenolic, etc., are often found in tape or film form. 

Typically tape or film epoxy adhesives are modified with synthetic thermoplastic polymers to improve flexibility in the uncured film and toughness in the cured adhesive. Epoxy resins can also be blended with phenolic resins for higher heat resistance. The most common hybrid systems include epoxy-phenolics, epoxy-nylon, epoxy-nitrile, and epoxy-vinyl hybrids. These hybrid film adhesives are summarized in Table 13.2, and structural properties are shown in Table 13.3. 

Property Modified epoxy Epoxy- phenolic Cyanoacrylate Polyamide Silicone rubber... 

C cured film (nitrile-phenolic, vinyl-phenolic, novolac-epoxy) 120°C cured film (modified epoxy, nitrile-epoxy, nylon-epoxy)... 

Most crosslinked thermosetting adhesives such as epoxies, phenolics, polyurethanes, and modified acrylics are highly resistant to many chemicals, at least at temperatures below their glass transition temperature. 

All of the commercial epoxy adhesives presented in App. B bond well to aluminum and to a wide variety of other materials. Sell22 has ranked a number of aluminum adhesives in order of decreasing durability as follows nitrile-phenolics, high-temperature epoxies, elevated-temperature curing epoxies, elevated-temperature curing rubber-modified epoxies, vinyl epoxies, two-part room temperature curing epoxy paste with amine cure, and two-part urethanes. 

Various adhesives can be used to bond polyphenylene oxide to itself or to other substrates. Parts must be prepared by sanding or by chromic acid etching at elevated temperature. Methyl alcohol is a suitable solvent for surface cleaning. The prime adhesive candidates are epoxies, modified epoxies, nitrile phenolics, and polyurethanes. Epoxy adhesive will provide tensile shear strength on abraded polyphenylene oxide substrates of 600 to 1300 psi and 1300 to 2200 psi on etched (chromic acid) substrates.71... 

Common adhesives for sandwich construction include nitrile phenolic films, modified epoxy pastes and films, epoxy-nylon films, polyimide films, and modified urethane liquid... 

The use of Mannich ba.scs mixed with other monomers or oligomers as modifiers of phenolic," ureic, " epoxy, etc., resins is reported. For instance, crosslinked structures of type 425 may be envisaged for the rapid curing of hydrophilic resins " obtained by reaction of acetone/formaldchyde/resorcinol oligomers (moiety A) with aminophcnol/ formaldehyde oligomers (moiety B). 

The reaction is catalysed by an organic base, usually an amine, which in the past has nearly always been the tertiary amine 2,4,6-tri(dimethyl aminomethyl) phenol. Such LP-modified epoxy resins have been in existence for more than 30 years. Their popularity declined because of the mercaptan odour of the polysulphide polymers in the uncured state and because of the use of a tertiary aromatic amine. 

It is possible to accelerate the rate of the polycondensation reaction by incorporation of special catalysts, resulting in urethane-urea-modified epoxy resin. The low-volatility alkyl phenol liberated in this reaction remains in the film as an external plasticiser. Owing to the different rates of the above two reactions, they have been synchronised to produce suitable polymer segments (Figure 10.9). 

Polyethylene and Polypropylene Acceptable bonds have been obtained between treated polyolefin surfaces with polar adhesives, such as epoxies, or solvent cements containing synthetic rubber or phenolic resin. The solvent adhesives are applied to both surfaces and the solvents allowed to evaporate before the parts are joined. Recommended epoxies are the anhydride-cured and amine-cured types. Also suitable is a two-component, polyamide-modified epoxy compound. Other adhesives that provide adequate bond strength to treated polyolefins include styrene-unsatmated polyester and solvent-type nitrile-phenolic (15). 

Polysulfone A number of adhesives have been found useful for joining polysufone to itself or to other materials. These include 3M Company s EC 880 solvent-base adhesive, EC 2216 room-temperaturecuring epoxy two-part paste, Bloomingdale Division, American Cyana-mid Company BR-92 modified epoxy with DICY curing agent, or curing agent "Z" (both spreadable pastes), vinyl-phenolics, epoxy-nylons, epoxies, polyimide, rubber-based adhesives, styrene polyesters, resorcinol-formaldehyde, polyurethanes, and cyanoacrylates. The EC 880, EC 2216, and the two BR-92 adhesives are recommended by the polysulfone manufacturer. Union Carbide (16) (17). 

Km Kem . [Kenrich Petrochemicals] Cun l phenol derivs. modifier for epoxy, fu and phenolic resins epoxy cure acoeleratm chemical hiteiii -ate. 

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