Epoxy resin Cycloaliphatic

There are three major types of epoxy resins cycloaliphatic epoxy resins (R and R are part of a six-membered ring), epoxidized oils (R and R are fragments of an unsaturated fatty acid, such as oleic acid in soybean oil), and glycidated resins (R is hydrogen and R can be a polyhydroxyphenol or a polybasic acid). The first two types of epoxy resins are obtained by the direct oxidation of the corresponding olefin with a peracid as illustrated by the following ... 

Chlorinated polyether Polysulphone Polytetrafluoroethylene Epoxy resin, amine-cured Epoxy resin, anhydride-cured The same filled with 65% of quartz flour The same filled with 65% of Al(OH)8 Epoxy resin, glass-laminated Epoxy resin, cycloaliphatic Expanded polystyrene Expanded polystyrene, flame-retardant Expanded polystyrene, extruded profile The same with flame-retardant Rigid polyurethane foam The same with flame-retardant Polysiocyanurate foam Flexible polyurethane foam Paraffin (candle)... 

Cycloaliphatic Epoxy Resins. This family of aUphatic, low viscosity epoxy resins consists of two principal varieties, cycloolefins epoxidized with peracetic acid and diglycidyl esters of cycHc dicarboxyhc acids. 

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. 

This reaction is quite general and, since the organic group R can be aliphatic, cycloaliphatic, or aromatic, there is wide scope for variation in the composition of epoxy resins. In practice, however, the most frequently used materials are those based on bisphenol A and epichlorohydrin, which represent over 80% of commercial resins. 

The DIBF OPPI combination has been shown to efficiently cure a wide variety of epoxies including cycloaliphatics. With this photoinitiator it is possible to cure bisphenol A epoxies such as Epon 828 quickly without the need for acrylation of the epoxy. Cycloaliphatic epoxies were of special interest because they were expected to react much faster than bisphenol A type epoxies. Those tested include 3,4-epoxycyclohexylmethyl-3 ,4 -epoxycyclohexyl-carboxylate (UVR 6110), bis(3,4 epoxy-cyclohexylmethyl) adipate (UVR 6128), and 1,2-epoxy-4-vinylcyclohexane (vinyl cyclohexene oxide). It was found that the vinyl cyclohexene oxide reacted rapidly, but work with it was discontinued because it has a fairly high vapor pressure (2 torr at 20 °C), an intense odor, and the photoinitiator does not dissolve in this resin. 

Curing agents account for much of the potential hazard associated with use of epoxy resins. There are several major types of curing agents aliphatic amines, aromatic amines, cycloaliphatic amines, acid anhydrides, polyamides, and catalytic curing agents. The latter two types are true catalysts, in that they do not participate in the curing process. 

The control resin network used in this study was a diglycidyl ether-based epoxy resin crosslinked with a cycloaliphatic diamine. Cooligomeric modifiers were prepared having varying percentages of TFP and DP siloxane and aminoethylpiperazine end groups. Both siloxane and ATBN and CTBN elastomers were used as epoxy modifiers, the latter two having been included to facilitate direct comparisons between modifiers in similarly prepared networks. 

Specialty Epoxy Resins. In addition to bisphenol, other polyols such as aliphatic glycols and novolaks are used to produce specialty resins. Epoxy resins may also include compounds based on aliphatic, cycloaliphatic, aromatic, and heterocyclic backbones. Glycidylation of active hydrogen-containing structures 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. 

Tpo maximize the utility of crosslinked cycloaliphatic epoxy resins in some of the more critical application areas, improved toughness is required. Such improvements can often be made through modification with various flexibilizing agents, but as a rule this improvement is accompanied by a severe degradation of the strength and heat distortion temperature of the cured system. 

In addition to the DGEB A resins, there are several other types of epoxy resins of commercial significance. The most common of these are epoxy novolacs, glycidyl ether of tetraphe-nolethane, bisphenol F-based resins, and aliphatic and cycloaliphatic resins. 

Aliphatic and Cycloaliphatic Resins. Aliphatic and cycloaliphatic epoxy resins have been produced from the epoxidation of olefinic compounds. The epoxidation process involves the use of an olefinic or polyolefinic compound and a peracid (e.g., peracetic acid) or other... 

Two types of epoxy resins are formed by this process (1) cycloaliphatic resins and (2) aliphatic resins. Of the many structures that can be synthesized by this process, the cycloaliphatic diepoxies offer the most interesting combination of properties. However, the aliphatic epoxy resins have the greatest utilization in epoxy adhesive formulation. 

The cycloaliphatic epoxy resins are characterized by the saturated ring in their chemical structure. They are almost water-white, very low-viscosity liquids. They provide excellent electrical properties such as low dissipation factor and good arc-track resistance, good weathering, and high heat distortion temperature. They are also free of hydrolyzable chlorine, sometimes present in DGEBA resins, which adversely affects certain electronic applications. 

Because of their low viscosity, cycloaliphatic epoxies are often used to dilute other epoxy resins. These resins, however, have not achieved general importance in adhesive formulations because of relatively low tensile strength and because they do not cure well at room temperature. One major application for cycloaliphatic epoxies, however, is for adhesives and coatings that can be cationically cured by exposure to uv light. 

Stevens, J. J., Cycloaliphatic Epoxy Resins, Chapter 2 in Epoxy Resin Technology, P. F. Bruins, ed., Interscience Publishers, New York, 1968. 

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. 

Their use in adhesive systems is minimal because they are relatively brittle and higher in cost than aromatic resins. However, cycloaliphatic epoxy resins are used in cationi-cally cured epoxy adhesive formulations. These are cured via uv or electron beam (EB) radiation. 

Other cycloaliphatic diamines such as isophorone diamine, bis-p-aminocyclohexylmethane and 1,2-diaminocyclohexane are used as epoxy resin curing agents for both ambient and heat cured epoxy resin systems. While they have advantages, such as light color and good chemical resistance, they provide rather sluggish cure rates at low temperatures. 

Suitable curatives for the polysulfide-epoxy reaction include liquid aliphatic amines, liquid aliphatic amine adducts, solid amine adducts, liquid cycloaliphatic amines, liquid amide-amines, liquid aromatic amines, polyamides, and tertiary amines. Primary and secondary amines are preferred for thermal stability and low-temperature performance. Not all amines are completely compatible with polysulfide resins. The incompatible amines may require a three-part adhesive system. The liquid polysulfides are generally added to the liquid epoxy resin component because of possible compatibility problems. Optimum elevated-temperature performance is obtained with either an elevated-temperature cure or a postcure. 

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