Nadic

A number of special purpose resins are available which employ somewhat unusual acids and diluents. A resin of improved heat resistance is obtained by using Nadic anhydride, the Diels-Alder reaction product of cyclopentadiene and maleic anhydride Figure 25.5). 

The methylated maleic acid adduct of phthalic anhydride, known as methyl nadic anhydride VI, is somewhat more useful. Heat distortion temperatures as high as 202°C have been quoted whilst cured systems, with bis-phenol epoxides, have very good heat stability as measured by weight loss over a period of time at elevated temperatures. The other advantage of this hardener is that it is a liquid easily incorporated into the resin. About 80 phr are used but curing cycles are rather long. A typical schedule is 16 hours at 120°C and 1 hour at 180°C. 

When cured with room temperature curing system these resins have similar thermal stability to ordinary bis-phenol A type epoxides. However, when they are cured with high-temperature hardeners such as methyl nadic anhydride both thermal degradation stability and heat deflection temperatures are considerably improved. Chemical resistance is also markedly improved. Perhaps the most serious limitation of these materials is their high viscosity. 

HO-Ar-OH = bisphenol-A HOOC-R-COOH = isophthalic, terephthalic, adipic, azelaic or nadic acid... 

GB Corgard (Sanofi Winthrop J Nadic (Dainippon) Nadolol (Mydal)... 

The resin is more than 90% DGEBA with the remaining material predominately at n=1. The curing agent, nadic methyl anhydride (NMA), is manufactured by Allied Chemical. The catalyst was benzyl dimethylamine (BDMA). All materials were stored in a desiccator to minimize moisture pickup. 

NADH. See also Nicotinamide adenine dinucleotide (NADH) biosensors for, 3 797 requirement as cofactor, 3 672-673 Nadic group, in creating polyimide thermosetting resins, 20 275... 

To improve the processability of PI and to alleviate or eliminate volatiles, work began in the late 1960 s under NASA Lewis sponsorship (23), to end-cap oligomers with reactive groups. The first report involved the use of 3,6-endomethylene-l,2,3,6-tetrahy-drophthalic anhydride (5-norbornene-2,3-dicarbo ylic anhydride, nadic anhydride) and alkyl derivatives thereof (e.g. citraconic anhydride) and 1,2,3,4-tetrahydrophthalic anhydride (4-cyclohexene-1, 2-dicarboxylic anhydride) as the reactive end group on imide oligomers (23-25). This initial effort led to the development of P13N [with T for polyimide, 13 for Mn of 1300g/mole and N for nadic end cap] whose structure is shown below. 

Nadic anhydride was also used to terminate an amic acid oligomer prepared from the reaction of 3,3 , 4,4 -benzophenonetetra-carboxylic dianhydride and 3,3 -methylenedianiline where the... 

Figure 2. Solid-state spectra of four different epoxies (hosed on the resin diglycidyl ether of bisphenol-A) are compared with the liquid-state spectra of their respective unreacted components, The chemical compositions are in Table I. Here the epoxies are identified by their main curing agent (a) PIP—piperidine (b) MPDA—metaphenylene diamine (c) HHPA—hexahydro-phthalic anhydride (d) NMA—nadic methyl anhydride.

Materials Description. Three CIBA-GEIGY epoxy/hardener systems were studied Araldite 6010/906, Araldite 6010/HY 917 and Araldite 6010/972 with stoichiometries 100/80, 100/80 and 100/27, respectively. Araldite 6010 was a DGEBA epoxy resin. The hardeners 906, HY 917 and 972 were, respectively, methyl nadic anhydride (MNA), methyltetrahydro phthalic anhydride (MTPHA) and methylene dianiline (MDA). These systems were investigated previously for the matrix controlled fracture in composites (6-8). The curing cycles used can be found in (6). The ideal chemical structures of the systems are shown in Table I. Neat resins were thoroughly degassed and cast into 1.27 cm thick plates for preparation of test specimens. 

Crosslinking of epoxy plastics through the hydroxyl groups of the repeat unit is used for prepolymers with low epoxide group contents. The most common curing agent is phthalic anhydride although other acid anhydrides such as tetrahydrophthalic, nadic methyl, and chloroendic anhydrides are used in specialty applications ... 

Norbomene end-capped polyimide oligomers (trade name LARC) are obtained by including 5-norbomene-2,3-dicarboxylic anhydride (nadic anhydride) (XLVII) in the polymerization reaction between a dianhydride and diamine [de Abajo, 1988 Hergenrother, 1987]. Heating the oligomer at 270-320°C results in a thermoset product. The main reaction... 

A further modification of the PMR-12F-71 resin comprises changing from the nadic endgroups to vinylphenyl endgroups, simply by using p-aminostyrene in the synthesis. This resin was called V-cap-12F-71 (see Fig. 37). The V-cap versions of PMR-II-50 (V-cap 11-50) and PMR-12F-71 (V-cap-12F-71) underwent a comparative long term thermal oxidative stability testing (112). Neat resin weight loss was measured at 343 °C in air over a period of 750 hours (Fig. 38). The data clearly indicate that the 12F-PMR resins exhibit excellent thermal oxidative stability and it also shows that the NE endcap is thermally less stable than the V-cap in the PMR-II series. 

Table lb. Infrared and Raman Band Assignments for Nadic Methyl Anhydride... 

Table lc. Infrared Special Changes During the Crosslinking of a Stoichiometric Nadic Methyl Anhydride/EPON 828 Mixture Catalyzed by 2.0% Weight Benzyldimethylamine... 

Resing and Moniz 60) cured DGEBA with three different curing agents, piperidine, hexahydrophthalic anhydride (HHPA) and nadic methyl anhydride (NMA). Spectra were collected with C-13 NMR using cross polarization and high power decoupling. 

Garroway, Ritchie, and Moniz 70 continued the characterization of epoxy polymers with respect to molecular motion using variable temperature, solid state C-13 NMR. DGEBA was the epoxy of interest. The DGEBA was cured with piperidine, m-phenylene diamine, hexahydrophthalic anhydride and nadic methyl anhydride. The piperidine cured DGEBA had the best resolved polymer spectra. This system... 

Nadic anhydride introduces polar groups into the polymer. These polar groups promote adhesion. However, it has a greatly different polymerizability from that of a norbornene monomer having no polar group. Therefore, the copolymerization reaction does not sufficiently occur. Better results are obtained with tetracyclododecene instead of norbornene (3). 

The introduction of functional groups is suitable to control the chemical and physical properties of the polymer. However, the introduction of functional groups may cause a reaction of the unshared electron pairs of the functional groups with the active catalytic sites. Thus, the active sites of the catalyst are destroyed. In order to overcome this problem, a procedure has been developed, where the functionalized monomers, such as maleic acid, nadic acid or their anhydrides are grafted after the polymerization reaction (4,37). Grafting takes place as a radical reaction, using e.g., dicumyl peroxide. Other attempts use excessive amounts of catalysts. 

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