TGDDM epoxies

The tetraglycldyl 4, 4 dlamlnodiphenyl methane epoxy (TGDDM) resins used were Hercules 3501-6 (catalyzed resin) and 3502 (uncatalyzed resin). The crosslinking reagent is 4, 4 ... 

Tetraglycidyl 4,4 diaminodiphenyl methane epoxy TGDDM (liquid at 23°C)... 

Figure 14.4 Chemical structures of two common epoxy chain extenders for PET (a) a diepoxide, e.g. Shell Epon 828, based on bisphenol A diglycidyl ether (b) a tetraepoxide, e.g. Ciba MY721, based on tetraglycidyl diaminodiphenyl methane (TGDDM)...

Epoxy film specimens of two different weight/weight ratios of TGDDM/DDS were evaluated (73/27 and 80/20). The films were cast between teflon sheets using a spacer. The cure cycle was 1 hr at... 

Figure 1. Dynamic mechanical spectra of 73127 and 80/20 TGDDM/DDS epoxy.

Figures 10 and 11 show a manufacturing application in which a resin s flow properties are measured in-sltu at a particular point in a thick laminate during cure in an autoclave. The sensor was inserted on the tool surface and in the center of a thick 192 TGDDM graphite epoxy laminate. Figure 10 shows the noise free raw data taken by the center sensor during cure in the 8x4 foot production size autoclave. Using the procedures described, the ionic mobility was measured at both the tool surface and the center of the thick laminate. In Figure 11, the sensor values of a show a 10 to 20 minute time lag in the point of maximum flow on the surface versus the laminate s center. Measurements of a versus q, as shown in...

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. 

For TGDDM/DDS (<35 wt% of DDS), Morgan and Mones [57] affirmed that all primary groups were consumed at 177°C after 2.5 hours of reaction. The epoxy-amine reactions dominate the early stages of cure and, hence, the composite processing conditions. 

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... 

As a representative example of cure monitoring using a common commercially used aerospace resin and a complex cure cycle, Figure 4.6 displays the output of epoxy system. This resin consists of a tetraglycidyl 4,4 -diamino diphenylmethane (TGDDM) and diamino diphenyl sulfone (DDS). This system with catalyst is sold by the Hercules Corporation as 3501-6. 

Figure 4.7 Log (oe"(co) versus log(viscosity) for the TGDDM epoxy-based on four isothermal runs...

Figure 4.11 TGDDM epoxy that has been aged at room temperature for 30 days after which it is cured in a press using a 130°C intermediate hold...

Figure 4.12 The lay up of a thick TGDDM epoxy (Hercules 3501-6) graphite laminate autoclave run showing the positions of the dielectric sensors and thermocouples...

Processing and Chemical Structure of TGDDM-DDS Epoxies Used in Composites Fabricated from Prepregs... 

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