Amines amine: epoxy mole ratio

Figure 8.1 DSC thermograms showing the curing of epoxy at different temperatures at a fixed amine to epoxy mole ratio of 1 1 I 40 C, II 55°C, III 60°C, IV 70°C, and V 100°C.

Figure 8.3 DSC thermograms indicating the effect of filler on curing at 70°C I no filler, amine to epoxy mole ratio 0.3 1, II 3.5 vol% 2C18-OM, amine to epoxy mole ratio 0.3 1, and III 3.5 vol% 2C18-OM, amine to epoxy mole ratio 0.2 1.

One of the key parameters defining the mechanical properties of the cured epoxy is the crosslink density. In a diepoxy fully cured with a diamine, if additional effects such as side reactions are neglected, each primary amine group is expected to react with two epoxide groups. Branched crosslinks result from this situation. With the chemical functionalities /a = 4 and /e = 2 of the diamine and the diepoxy molecules, respectively, the amine/epoxy mixing ratio, r, is given by Eq. (1), where and Ng denote the respective numbers of moles [10]. 

Figure 7.4 Mass fraction of sol as a function of the mole ratio of amine and epoxy groups (O) experimental data, (—) calculated dependences taking epoxy conversion, x, into account. 

Figure 2.16. Cure of different epoxy-amine systems at 100°C PGE-aniline in molar ratios of amine/epoxy functional groups r = 0.6 (1) andr = 1.0 (2) DGEBA-aniline with r = 0.7 (3) and r = 1.0 (4) PGE/A,A -dimethylethylenediamine at 30°C is given for comparison (5) (a) non-reversing heat flow per mole of reacted (epoxy-NH) functional groups (b) heat capacity change per mole of reacted (epoxy-NH) functional groups.

The anhydrides are usually used at ratios of 0.85 1.1 moles anhydride carboxyl group per epoxy equivalent. Lower ratios down to 0.5 1 may, however, be used with some systems. The organic bases are used in amounts of 0.5-3%. These are usually tertiary amines such as a-methylbenzyldimethylamine and n-butylamine. 

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