Diamine hardeners

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. 

Table 2.8 Main diamine hardeners used in epoxy systems... 

Amino and functional aromatic phosphates, phosphonates, and phosphine oxides have also been used as reactive components to impart flame retardancy to cured epoxy resins. Phosphine oxides are particularly hydrolytically stable and several studies have been reported, for example, of the curing of epoxy resins with bis(aminophenyl) alkyl and aryl phosphine oxides65-67 (Structure 5.19). The relative performances of epoxies cured with aromatic diamine hardeners containing phosphine oxide, phosphinate, phosphonate, or phosphate units have recently been assessed.68 Aromatic phosphine oxides have been functionalized also with maleimide and hydroxyl groups for use as epoxy resin hardeners.69,70... 

Recently, the dynamic mechanical properties of the resins cured with a series of linear poly anhydrides having the structures shown in Table 5 were studied by Ramon41 . The dynamic mechanical properties are very similar to those of the resins cured with diamine hardeners as shown in Fig. 10. The relationships between the number of CH2 groups n and Tg Eire shown in Fig. 8. Tg drops rapidly below that of an alkyldiamine-cured resin as n increases. This is considered reasonable because, compared with the hardener.unit in an amine-cured resin, the acid anhydride segment existing in the main chain of the anhydride-cured resin is twice as long. 

The structure of DICY resembles that of diamine hardeners but the dynamic mechanical properties of the resin cured with DICY is far different from that of the diamine-cured resin in Fig. 2 (Figs. 13 and 14)47). 

Active groups on the curing agent, or hardener , molecules open the reactive epoxide rings to produce crosslinks. For example, a diamine hardener... 

Figure 24.11 Comparison of corrosion protection characteristics of nanocomposites prepared with the addition of free molybdic acid and bound molybdate as a mono salt of the diamine hardener.

With aromatic diamines or cycloaliphatic diamines hardened epoxy resins... 

Glass/epoxy Diamine hardener Glass/epoxy... 

Hycai Reactive Liquid Polymers Preliminary Data Sheet AB-16, Hycai Reactive Liquid Polymer Modified Epoxy Adhesives Polyether Diamine Hardeners, BFGoodrich, August 1983. 

Figure 5.1 Typical epoxy resin and hardening reaction using a primary diamine hardener, (a) A bisphenol A-epichlorohydrin based epoxy resin. The most important type is when n 0.2 and the liquid resin is essentially (b) a simple diglycidyl ether of bisphenol A (DGEBA). (c) A primary diamine hardener, (d) a crosslinked, thermosetting epoxy adhesive.

Araldite AY18/HZ118 (epoxy/diamine hardener) SBD Certite 19-19 (filled polyester) 2-4-3-1 9 -] Shields (1976a)... 

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