Aromatic epoxy resin

Andersen, M., Kiel, P, Larsen, H. Maxild, J. (1978) Mutagenic action of aromatic epoxy resins. Nature, 276, 391-392... 

Cycloaliphatic and heterocyclic epoxy have better weather resistance and less tendency to yellow and chalk than do aromatic epoxy resins. These resins possess excellent electrical properties and are often used in electrical and electronic applications. They are generally formulated into casting and filament winding compounds. 

Metal curing salts function with aliphatic or aromatic epoxy resins in the presence of trace water. 

For laboratory use and, perhaps, for small-volume production, another first stage can be added. Microreactors, which require much less solvent, are being studied for fluorina-tion,6 DNA chips, and other uses.7 A variation on item 2 is the use of a polyhydroxyester based on aromatic epoxy resins and aliphatic carboxylic acids to reduce the loss of styrene from unsaturated polyester resins by 95-99%.8... 

Aliphatic epoxy resins generally have higher color stability and reactivity than aromatic epoxy resins, but their resistance to aqueous acid solutions is much lower. 

Powder coatings based on aromatic epoxy resins have high chemical and mechanical resistance, but are not resistant to weathering. To obtain weather-resistant powders, triglycidyl isocyanurate (Araldite PT 810, Ciba-Geigy Tepic, Nissan) must be used as the epoxy component with carboxy-functional polyesters. 

Shear yielding is well established as the principal deformation mechanism and source of energy dissipation in both uiunodified and rubbo -toughened epoxy resins [2,3,27,83,121]. As molecular mobility in the epoxy resin network chains decreases, the ability of the matrix to deform by shear yielding is reduced. This is the reason why epoxy resins become both more brittle and more difficult to toughen as the epoxy resin crosslink density increases and/or as the network chains increase in rigidity, e.g. by use of highly aromatic epoxy resin monomers (see Section 19.7.1.1). 

Several nitrogen-containing aromatic epoxy resins were also commercialized. These are condensa-... 

Several nitrogen-containing aromatic epoxy resins were also commercialized. These are condensation products of aromatic amines with epichlorohydrin. Following are some examples [140] ... 

The bisphenol A novolac epoxy resin is a non-ionic aqueous dispersion of a polyfunctional aromatic epoxy resin. It contains reactive epoxide functionality and is intended for high performance applications which require maximum chemical and solvent resistance and/or elevated temperature service. This thixotropic dispersion contains no organic solvent and is completely water reducible. Upon evaporation of water, the novolac epoxy coalesces to... 

The epoxy resins based on aliphatic alcohols are interesting because they impart flexibility to the final product, and the glass transition temperature, Tg, is lower than for aromatic epoxy resins, which can be an important feature when the cure is close to room temperature. The aliphatic resins should be useful products in civil engineering, where cure at room temperature is necessary. 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

Reactive (unsaturated) epoxy resins (qv) are reaction products of multiple glycidyl ethers of phenoHc base polymer substrates with methacrylic, acryhc, or fumaric acids. Reactive (unsaturated) polyester resins are reaction products of glycols and diacids (aromatic, aUphatic, unsaturated) esterified with acryhc or methacrylic acids (see POLYESTERS,unsaturated). Reactive polyether resins are typically poly(ethylene glycol (600) dimethacrylate) or poly(ethylene glycol (400) diacrylate) (see PoLYETPiERs). 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Specialty Epoxy Resins. In addition to bisphenol, other polyols such as aUphatic glycols and novolaks are used to produce specialty resins. Epoxy resins may also include compounds based on aUphatic, cycloaUphatic, aromatic, and heterocycHc backbones. Glycidylation of active hydrogen-containing stmctures with epichlorohydrin and epoxidation of olefins with peracetic acid remain the important commercial procedures for introducing the oxirane group into various precursors of epoxy resins. 

Aromatic and Heterocyclic Glycidyl Amine Resins. Among the specialty epoxy resins containing an aromatic amine backbone, the following are commercially significant. 

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. 

There is, quite clearly, scope or a very wide range of epoxy resins. The nonepoxy part of the molecule may be aliphatic, cycloaliphatic or highly aromatic hydrocarbon or it may be non-hydrocarbon and possibly polar. It may contain unsaturation. Similar remarks also apply to the chain extension/cross-linking agents, so that cross-linked products of great diversity may be obtained. In practice, however, the commercial scene is dominated by the reaction products of bis-phenol A and epichlorohydrin, which have some 80-90% of the market shtu"e. 

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

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