Diepoxide-diamine systems

This value is close to experimental values of gel conversion reported for several diepoxide - diamine systems. 

General concepts will be analyzed by stating kinetic equations for a diepoxide diamine system in stoichometric proportions, and under condi-... 

As discussed in Chapter 4, for many thermosetting polymers a unique relationship may be established between conversion and glass transition temperature, as was also verified for this particular diepoxide-diamine system (Wisanrakkit and Gillham, 1990). So, the left-hand side of Eq. (5.46) may be written as a unique function of Tg, F(Tg)... 

Fig. 14. Dependence of the critical value of the conversion of excess epoxy groups available for polyetherification, in diepoxide-diamine systems on the initial molar ratio of epoxy to amino groups 1 dependence calculated using the kinetic theory, 2 dependence calculated using the kinetic theory.

Riccardi, C.C. and Williams, R.J.J. (1992) Influence of prepolymerixation on gelation of diepoxide diamine systems. Pdytner,... 

However, for an alternating bicomponent system (like in diepoxide-diamine addition) both formulations give the same result. These problems are exposed in more detail in Ref. 

The concept of an ultimate conversion lower than 100% is reasonable in view of steric restrictions in a highly crosslinked network. Oleinik has reported an ultimate conversion of 92% in a diepoxide-diamine stem. This ultimate conversion value is attributed to topological limitations and is consistent with computer simulations Hale reports an experimental ultimate conversion of less than 85% for a 1 1 stoichiometry ECN-phenolic cresol novolac (PCN) system which is similar to the one in this study. The lower ultimate conversion seen in the ECN-PCN stem is in agreement with greater steric hindrances arising from the cresol pendant group. The topological constraints on the ultimate conversion will increase as functionahty of the reactive molecules also increases. 

The functionality of precursors varying between/ = 2 and/ = 6 is considered to be low (Figure 5.2). Polyurethane networks prepared from bifunctional telechelics and trifunctional triisocyanates, diepoxide (f = 2)-diamine (f = 4) systems, diepoxide if = 4)-cyclic anhydride (/ = 2) systems, phenol (/ = 3)-formalde-hyde if = 4) resins, or melamine (/ = 6)-formaldehyde (/ = 2) resins are in this category. 

Figure 5.7 shows the superposition of Tg vs lnt data for the diepoxide (DGEBA)-aromatic diamine (TMAB) system, to form a master curve at 140°C (Wisanrakkit and Gillham, 1990). Vitrification times, defined as the time at which Tg equals the cure temperature, are marked by arrows (Tg was defined as the midpoint of the baseline change during a DSC scan). 

As an additional component, various thermoplastic polymers can be used. As a binder for copper clad laminates, a solution of solid epoxide resin (Epikote 1001), BPA/DC prepolymer, Zn acetate and poly(phenylene sulfide) was used [83], Other binders for reinforced plastics contain polysulfone. Such compositions consist of liquid BPA/ECH epoxide resin, BPA/DC prepolymer, polysulfone and bis(4-hydro-xyphenyl)sulfone [85]. Bis(4-aminophenyl)sulfone can be also added [86]. In such systems the bisphenol reacts with the epoxide resin as a chain extension agent, whereas the diamine crosslinks the diepoxide. The Tg values are close to 200 °C. They can be increased a little, if the BPA/ECH epoxide resin is replaced by the tetra-epoxide A,A,A, A -tetrakis(2,3-epoxypropyl)diaminodiphenylmethane [87]. 

The advantage of this procedure consists in the possibility that the structures generated in (b) are still finite. This method was applied to the treatment of nonlinear initiated polymerization of a monomer carrying two polymerizable groups and also to gelation of diamine-diepoxide systems This application will be explained in more detail in Section 4. 

The extinction probabilities necessary for obtaining the structural characteristics beyond the gel point are defined by Eq. (20). For the diamine-diepoxide system we have... 

In order to obtain a phase diagram in conversion-composition coordinates, a particular system consisting of a diepoxide based on diglycidylether of bis-phenol A (DGEBA), a stoichiometric amount of a diamine (4,4 -diamino-3,3 -dimethyldicyclohexyl-methane, 3DCM), as a hardener, and a rubber based on a statistical copolymer of butadiene and acrylonitrile, will be considered [65]. The increase in the number-average molar mass for the polycondensation of a stoichiometric diepoxy-diamine mixture, is given by [65]... 

A linear-chained epoxy resin was formulated from phenyl glycidyl ether and nadic methyl anhydride, catalysed by benzyldimethylamine (248). An IR fibre-optic probe was used to follow the conversion of a thermosetting tetrafunctional epoxy resin in which the hardener was an aromatic diamine and a carboxylic dianhydride. A polymerisation system consisting of a cycloaliphatic diepoxide, epoxidised natural rubber (ENR), glycidyl methacrylate (GMA) and a cationic photoinitiator, triphenylsulfonium hexafluoro-antimonate, was studied (75). Multifunctional epoxy/ amine formulations (Epon 825 plus 4,4 -methylene-... 

Figure 3.15 Fraction of elastic chains, Ve/[F10], as a function of conversion, for a diepoxide (B2) - diamine (A4) stoichiometric system, with the following kinetic parameters R21 = 0.4, (OH)o/F20 = 0.061, and k i/(kiF20) = 0.0576.

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