TGDDM/DDS resin

Other possible reactions, such as homopolymerization (epoxide+epoxide) and epox-ide+hydroxyl group (in the latter stages of cure), can be neglected when the ratio of epoxide to amine is stoichiometric and in the absence of catalyst or accelerator [194], For TGDDM/DDS resins, the homopolymerization reaction may be neglected at cure temperature below 180°C [84], At temperatures between 177°C and 300°C, dehydration and/or network oxidation occur, which results in formation of ether cross-linkings with loss of water. Decomposition of the epoxy-OH cure reaction can also take place, which results in propenal... 

Specimens of probe-containing TGDDM/DDS resin cured at 150 C produced Ip vs cure time profiles similar to the... 

Fig. 3. Liquid water uptakes for a TGDDM-DDS neat resin at increasing applied hydrostatic relative pressures. (22)...

Fig. 6. First (open circles) and second (full circles) equilibrium moisture sorptions in the TGDDM-DDS neat resin...

The free volume model seems to be more adequate to describe the plasticization behaviour of the systems of lower amine content. According to Eq. (5), the higher is the change of the expansion coefficient the lower is the influence of the diluent volume fraction. The three TGDDM-DDS mixtures cured with 20, 30 and 50 PHR of hardener were characterized l2) by changes of the expansion coefficient at the glass transition, respectively, of 0.63, 1.08 and 2.94x 10 3 °C l. The more dense and stiffer resin crosslinked with 50 PHR of DDS should be, in principle, the less... 

Neat Epoxv Resin. Neat epoxy resin (TGDDM/DDS) was found to be a relatively weak emitter of photons, electrons and positive ions. The general shape of all the emission curves consists of a relatively rapid burst, followed by a very low intensity decay which lasts approximately 100 jis. We frequently observed that during... 

Han et al. [191] found that the rate of cure of a resin is greatly influenced by the presence of fibers and the type of fibers employed. The rate of reaction for resin-fiber system can be 60 percent different from that of neat resin, after a 10-min cure. A similar conclusion was presented by Mijovic and Wang [192] for graphite-epoxy composites based on TGDDM/DDS (33phr). They verified large differences (see Table 2.5) in the kinetic parameters when considering an autocatalytic model. 

H and 19F NMR were used to study the interaction of the individual resin components of the C-fiber/TGDDM-DDS prepregs with BF3 NH2C2HS. 

The catalyst composition in Fiberite 934 and Hercules 3501 prepregs was investigated by 19F NMR. The epoxy resin in these commercial C-fiber/TGDDM-DDS prepregs was dissolved in DMSO. 

Numerous studies have been reported on the effect of diffusion of water into epoxy resins 177 178>. It is generally agreed that moisture acts as a plasticizer which lowers the Tg of the resin uo 134). Very little work, however, has been reported on the effect of physical aging on the diffusion behavior of water into network epoxies. This Section of the review summarizes the first attempt to study such an effect on TGDDM-DDS epoxy/water interactions. 

In order to help to identify the various resonance peaks in the solid-state NMR data, it was necessary to measure the solution NMR for each of the components in the neat resin. Carbon-13 NMR spectra measured at 125 MHz of TGDDM, DDS, and DGOP dissolved in deuterated chloroform are shown in Fig. 40-44. 

Figure 17. Dynamic viscosity profiles for the TGDDM/DDS neat resin including isothermal holds at 115, 135, 155, and 170 °C.

Figure 2. Stress chemiluminescence of epoxy resin (TGDDM/DDS) at 80°C in...

For TGDDM/DDS the values 1 = 2 and m + n = 2 enabled a good fit for DSC data for up to 70% conversion, after which diffusion control of the reaction rate became dominant. The difficulty with this type of approach is that for each different resin it is necessary to determine not only new pseudo-rate constants but also new values for the exponents (Lee et al, 1992, Mijovic and Wang, 1986). This supports the view that the exponents are more akin to curve-fitting parameters rather than being a true reflection of the underlying reaction mechanisms involved. 

Figure 3.10. Change in spin population with time of cure of the TGDDM epoxy resin MY720 cured with 26.5% DDS at 160 °C. Brief UV irradiation is used to create the radical cation species analysed. Reproduced with permission from St John (1993).

Figures 3.16(a) and (b) show the MIR spectra in two spectral regions for the TGDDM resin (Ciba MY721) and the aromatic amine hardener DDS as well as the mixture containing 27% DDS, which is typical of commercial formulations used in composite materials. The assignments of the significant bands in the spectra are given in Tables 3.2 for the TGDDM (MY721 resin) and 3.3 for DDS.

Epoxy resin (TGDDM/DDS) (Sourour and Kamal, 1976) Thermosets (Gonzalez-Romero and Casillas, 1989)... 

Dusi et al. (1987) examined the chemorheology of Fiberite976 resin (TGDDM/DDS). The chemoviscosity is described by a simple Arrhenius relationship as shown by the following equation ... 

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