Epoxy functional resins

Many photoinitiator systems have been developed which are capable of producing acidic products. Most of these cationic photoinitiators are based on some form of onium salt which (in the absence of light) is stable in the presence of epoxy functional resins. Following irradiation, an acidic catalyst is produced which can initiate the formation of polymer. 

Since epoxy functional resins are widely available and contribute many desirable characteristics to coatings such as adhesion, toughness and abrasion resistance, it may be desirable to have UV-curable adhesives based on epoxy systems. In conventional UV-curable coatings, the... 

Direct and sensitized photolysis of diaryliodonium and triarylsulfonium salts, as well as sensitized photolysis of phenacylsulfonium salts, yields both cationic and radical initiators (see Volume 4, Chapter 20). Accordingly, triarylsulfonium salts have been used for photocrosslinking mixtures of acrylate- and epoxy-functional resins, as well as acrylate- and vinyl ether-functional resins with suppression of air inhibition. 

Enhanced cure rates and cure depths,as well as desirable application and film properties, have been reported for photocrosslinking mixtures of acrylate- and epoxy-functional resins using mixtures of photoinitiators for radical and cationic polymerization. 

Formulated Melamine resin + epoxy-functional silane... 

Figure 7. Paint adhesion loss in salt spray exposure (ASTM B117) as a function of ester content for chain-extended epoxy-amine and epoxy-ester resin based coatings. All coatings applied at 20-25 urn film thickness to SAE 1010 steel test panels, baked, scribed and exposed for 24 hours to salt spray conditions.

Eckert et al. (2) prepared curable dental compositions consisting of epoxy functionalized carbosilane derivatives, (I). Carbosilanes, ( ), were prepared by Chappelow et al. (3) and used in dental matrix resin systems, such as restorative composites. 

Shih et al. [60] studied the modification of a novolac-type epoxy resin with PDMS to overcome brittleness and poor impact resistance. This kind of resin is typically cured via their epoxy functions. The authors also introduced isocyanate monofunctionalized PDMS. Hence, the common treatment with MDA (4,4 -methylene dianiline) not only cured the resin on the one hand, but also made it possible to form the branched copolymer. Mechanical and thermal analyses showed that an optimum in isocyanate-terminated PDMS content was required to reach good thermal and physical properties and low moisture absorption. 

Epoxy Novolac and Other Phenols. Resins of greater functionality than DGEB A can be produced in several ways. Polyols having more than two hydroxyl groups per molecule (e.g., phenol novolac resins) can be reacted with epichlorohydrin to produce epoxy novolac resins with a structure shown in Fig. 2.5. 

Of course, in the case of both curing agents and catalysts, suitable adjustments will have to be made for the presence of nonreactive fillers and modifiers. Such ingredients can be liquids such as a solvent, a hydrocarbon resin, or a plasticizer. Since they do not contribute any epoxide functionality, they should not be considered when one is determining stoichiometry. However, if the additives have epoxy functionality, such as in the case of reactive diluents, the stoichiometric calculations will have to take these materials into consideration, by calculating ratios similarly as with an epoxy resin. 

Skin. Most epoxy resins are not acutely irritating to the skin. However, they are capable of causing skin sensitization. Susceptibility to skin irritation and sensitization varies from person to person. The epoxy resins are considered to be milder skin sensitizers than amine-type curing agents or epoxy functional reactive diluents. 

The repeat unit of bisphenol F epoxy resins (Figure 2.3) or epoxy novolac resin does not significantly increase the epoxy equivalent weight although viscosity and functionality do increase (Helfad, 1996). 

F yrolysis of gaseous hydrocarbons at 1000-1700 °C is a common route (cf. Nos. 6 and 7 in Table 9, where two examples involving benzene are considered [441, 442]). The substrate was nickel, and dense black layers were obtained to serve as a host lattice for the lithium negative electrode. The pyrolytic carbon from benzene at 1000 °C gave a lithium GIC (CeLi) and could be cycled at 99% current efficiency [407]. Pyrolysis of epoxy Novolac resin and epoxy-functionalized silane gave a material containing silicon with a capacity of 770 mAh/g for the lithiated form [443]. 

The commercially available phenoxy resin has Mw around 50,000 and little epoxy functionality. The phenoxy polymer is then classified as a polyol or a po-ly(hydroxy ether) [3]. Typical applications for the phenoxy resin are as hot-melt adhesives, coatings for beverage cans, and toughening agents for various epoxy resin formulations. The viscoelastic properties of phenoxy resins have been studied by Alegria et al. [11-15]. The phenoxy polymer can be used as a reference in the viscoelastic study of DGEBA oligomer. 

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