Flexibility epoxy resin

FIGURE 2.9 An idealized structure of a flexible epoxy resin made from a polyol.11... 

Glycidyl ethers of aliphatic polyols based on polyglycol, glycerin, and other polyols are flexible epoxy resins. They are used as reactive diluents and flexibihzers for solvent-free epoxy resin formulations. Epoxy-polyglycol resins that are produced from the reaction of epichlorohydrin and polyester polyols based on ethylene or propylene oxide are the most common of these types of flexible epoxy resins. Examples of typical commercial aliphatic epoxy resins are shown in App. C. 

Commercial products are available where n varies from 2 to 7. The flexible epoxy resins based on polyglycol also make excellent reactive diluents because they have a viscosity of 100 cP at 25°C. Table 4.4 shows the effect of two polyglycol diepoxides on the physical properties of a cured epoxy system. Another type of flexible epoxy resin is derived from dimerized unsaturated fatty acid, cashew nut oils, and other vegetable oils. Other flexible epoxy resins can be made with thiols, aliphatic acids, and hydroxyl-terminated compounds. Applications where flexible epoxy resins are valued include... 

VERs are available as both rigid and flexible epoxy resins. The flexible epoxy resins generally have a depressed glass-transition temperature, Tg, and inferior chemical resistance. Nitrile-rubber-modified VER (I) appeared on the market in the mid- to late 1970s. These elastomer-modified VERs show improved fatigue resistance over unmodified VER (2). 

Flexible epoxy resins were synthesized by the polymerization of epoxy compounds in the presence of an unsaturated alcohol (Scheme 56) followed by the epoxidation of the double bond with PAA. If a glycidyl ether of a cyclohexenyl ring-containing alcohol is used as the epoxy compound, a polyether-epoxy resin is obtained (Scheme 57). The polymerization of 3-cyclohexenyl-1-methyl glyci-... 

Uses Crossiinked polymer polyol/styrene-acrylic resin comonomer in electrodeposition, adhesives, photographic materials, flexible epoxy resins, marine and automobile coatings impurity in the mfg. of isocyanatoethyl propionate Manuf./Distrib. Kowa Am. http //www.kowa.com/chemicai/... 

Epoxy resin systems of the bisphenol A-epichlorohydrin t)rpe and epoxy novalac type generally lack flexibility. There are a number of proprietary flexible, low viscosity epoxy resins used to modify the above types to provide better impact resistance, elongation, or flexibility. These flexible epoxy resins are true epoxies and react completely with epoxy curing agents and becomes a permanent part of the cured system. However, they do not contribute towards lowering costs. 

These materials are used to improve thermal and mechanical shock, increase elongation, and obtain higher impact strength and flexibihty. Usually, there is some sacrifice of physical strength, electrical properties and chemical or solvent resistance, and elevated temperature performance. Flexible epoxy resins or monofunctional epoxide compoimds are examples of reactive epoxide-type modifiers. They can be used at ratios up to 1 1 to obtain a flexible and rubbery cured epoxy compound. They are shelf-stable when blended with the resin. 

Most of the BPA-based epoxy resins are quite rigid and are based on petrochemicals. A quite different type of flexible epoxy resin is based on cardanol, derived from cashew nut shell liquid. Mono-, di- and multifunctional derivatives are possible. Mono- and difunctional low viscosity derivatives are used as modifiers and diluents, while complex di- and multifunctional epoxies are used in two-component ambient cure epoxy systems. They give the cross-linked matrix excellent flexibility, toughness and impact resistance. They possess very good water, chemical and corrosion resistance. 

Long chain aliphatic epoxy resins based on a poly glycol or a vegetable oil fatty acid, when reacted with epichlorohydrin, are used as additives to flexibilize epoxy resin adhesives. They are not used alone because of their water sensitivity and overall lack of toughness. They serve as modifiers for Bisphenol A based epoxy resins. An idealized structure for flexible epoxy resins is shown below ... 

Examples of typical aliphatic epoxy resins based on polyol propylene glycol are D.E.R. 732 and D.E.R. 736 (Dow). Epi-Rez 505 (In-terez) and Heloxy WC-85 (Wilmington Chemical) are typical flexible epoxy resins based on a vegetable oil fatty acid. 

Figure 5 Chemical formulae of epoxy reactive diluents such as phenylglycidyl ether 28 and butanediol diglycidylether 29 and flexible epoxy resins including polyoxypropylene-a, (o-diglycidyl ether 30, diglycidyl ester of linoleic acid dimer 31, and epoxy novolac resin of...

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