Epoxy systems, toughness

Glycidyl Ethers of Aliphatic Polyols. Glycidyl ether epoxy resins based on polyols provide greater flexibility and lower softening temperatures for the final cured epoxy system. The polyol is reacted with epichlorohydrin to produce these resins. These resins are generally not used alone because of water sensitivity and overall lack of toughness. However, they serve as modifiers for DGEBA-based epoxy resins. An idealized structure for a flexible resin based on this chemistry is shown in Fig. 2.9. 

Diglycidyl ether of ethoxylated resorcinol (DGER), a resorcinol-based epoxy monomer, can be cured with various epoxy curing agents to yield a balance of flexibility, low viscosity, and fast cure capability.12 The molecular flexibility of DGER is claimed to improve the impact strength and fracture toughness of the cured epoxy system. These flexibilized... 

However, newer adhesives systems having moderate temperature resistance have been developed with improved toughness but without sacrificing other properties. When cured, these structural adhesives have discrete elastomeric particles embedded in the matrix. The most common toughened hybrids using this concept are acrylic and epoxy systems. The elastomer is generally a amine- or carboxyl-terminated acrylonitrile butadiene copolymer (ATBN and CTBN). 

Another development has been reported by P.A. Lucas, W.E. Stamer and S.G. Musselman of Air Products and Chemicals Inc. (Lucas et al., 1994). An acrylate functional urethane flexibiliser has been used to modify epoxy resin, which optimises reactivity and is more compatible with epoxy. Urethane-acrylate flexibiliser offers very tough hybrid epoxy systems meeting the more demanding requirements of civil engineering applications. 

The important maintenance coating area, particularly for pipe and tank coatings, is served by epoxy systems cured with polyamine or polyamidamines. Two-component, air-dried, solventless systems used in maintenance coatings provide tough, durable, nonporous surfaces with good resistance to water, acids, alkalies, organic solvents, and corrosion. 

In the case of abrasive freight goods, the interior of the car must be lined with a thick coat system consisting of solvent-free two-pack polyurethane or epoxy material. Toughness combined with flexibility results in a film that is highly resistant to abrasion. 

Ma Ma, J., Mo, M.-S., Du, X.-S., Rosso, P., Friedrich, K., Kuan, H.-C. Effect of inorganic nanoparticles on mechanical property, fracture toughness and toughening mechanism of two epoxy systems. Polymer 49 (2008) 3510-3523. 

Mos Mostovoy, S., Ripling, E. J. Eracture toughness of an epoxy system. J. Appl. Polym. Sci. 10 (1966) 1351-1371. 

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