BDMA

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. 

Tanaka and Kakiuchi (6) proposed catalyst activation via a hydrogen donor such as an alcohol as a refinement to the mechanism discussed by Fischer (7) for anhydride cured epoxies in the presence of a tertiary amine. The basic catalyst eliminates esterification reactions (8). Shechter and Wynstra ( ) further observed that at reaction conditions BDMA does not produce a homopolymerization of oxiranes. 

The resin contained 100.00 parts Epon 828, 80.00 parts NMA and 2.00 parts of BDMA. A part is a unit of mass. This formulation yields a resin with good mechanical performance. The formulation was cured in small test tubes that were placed in an electrically-heated, forced-air circulating oven which was controlled within 0.1°C of the set temperature. Specimens were removed with increasing time, thermally quenched and stored at -25°C. 

Three of the four resins yield extracts of the functionality of Equation 4. The slope of the exponential decay allows for the evaluation of x. The resin, see Table II, initiated by benzyl dimethyl amine (BDMA) at the stated cure cycle, when subjected to leaching yields an extract of low solubility and a distribution of oligomeric molecules of low number average molecular weight. 

Figure 4.8 FDIR spectra of phenol (A) and the phenol-BDMA complex (B). (Reproduced with permission from ref. 18.)...

FIGURE 11.9 Displacement separation of a crude MSH mixture with the same column used as in Figure 11.8. Carrier 0.25% formic acid, 0.5% triethylamine, 19% acetonitrile displacer, 50mM BDMA in 0.25% formic acid, 0.5% triethylamine, 21% acetonitrile. Flow rate O.lmL/min feed 35 mg MSH. (Reprinted with permission from Shukla, A.A. et ah, Biotechnol. Prog., 14, 92, 1998. Copyright 1998, American Chemical Society.)... 

Figure 16.5 Examples of the intramolecular donor-acceptor system and their emission spectra-aryl derivatives of ALV-dimethyl-aniline BDMA 4-(9-acridyl)-lV,lV-dimethylaniline, ADMA 4-(9-anthryl)-A,A-dimethylaniline, PDMA 4-(l-pyrenyl)-A,A- dimethylaniline, and NDMA 4-(l-naphthyl)-A,A-dimethylaniline. (See the color version of this figure in Color Plates section.)...

Table 3. Least-Squares Analysis 2000-1400 cm 1 of 1 1 Stoichiometry Anhydride Epoxide Mixtures (0.5% wt BDMA Catalyst) Crosslinked at 90 °C...

Fig. 1. Difference spectrum depicting the infrared spectral changes accompanying the 80 °C cross-linking of a stoichiometric mixture of EPON 828 and NMA with 2.0% weight BDMA catalyst...

A survey of the extensive literature of kinetic results reported for epoxy-anhydride-tertiary amine systems is surprising. Both nth order and autocatalytic expressions have been reported for the same system. As an example, we analyze the results reported for the copolymerization of a diepoxide based on diglycidyl ether of bisphenol A (DGEBA) with methyl-tetrahydrophthalic anhydride (MTHPA), initiated by benzyldimethylamine (BDMA). 

Hexahydrophthalic anhydride (HHPA) is a low-melting-point (36°C) solid. It is liquefiable at temperatures of 50 to 60°C and can be mixed easily with hot epoxy resins. The mixed resins are characterized by low viscosity, long pot life, and low exotherm. Because of its low reactivity HHPA is generally used with an accelerator, usually BDMA or DMP-30. 

HHPA is generally used in a concentration between 55 and 80 pph depending on the nature of the epoxy resin. The viscosity is generally about 200 cP at 40°C when mixed with a DGEBA epoxy resin. A typical cure schedule for a 0.5 to 2 percent BDMA catalyzed system is 2 h at 80°C plus 1 h at 200°C. Typical of all the anhydride curing agents, the cured epoxy will demonstrate high heat distortion temperatures and excellent chemical resistance. 

The DMP designation comes from the original manufacturer of these chemicals, Rohm and Haas, and continues today with their manufacturer, Resolution Performance Polymers LLC. There are other tertiary amine catalysts such as benzyldimethylamine (BDMA), primarily salts of the above, and substituted imidazoles. 

Benzyldimethylamine (BDMA) is another tertiary amine that can be used as either a sole catalyst or an accelerator with other curing agents. It is used with DGEBA epoxy resins at 6 to 10 pph. The pot life is generally 1 to 4 h, and the cure will be complete in about 6 days at room temperature. When used by itself, BDMA can provide epoxy adhesive formulations with high-temperature resistance (Chap. 15). However, BDMA is mostly used as an accelerator for anhydride and dicyandiamide cured epoxy resins. 

Dicyandiamide is a true latent catalyst for epoxy resin curing. It is also considered to be the workhorse of one-component adhesives due to its ease of use, excellent performance properties, long shelf stability, and low toxicity. In certain admixtures with DGEBA, it has demonstrated a room temperature storage life in excess of 4 years. Dicyandiamide is usually added to the solid epoxy resin in concentrations of about 3 to 6 pph. It melts at about 150°C. Cures can be conducted in the range of 120 to 175°C but are very slow at the lower temperatures. As a result, it is common practice to add accelerators such as benzyl-dimethylamine (BDMA) and mono- or dichlorophenyl substituted ureas to these systems. 

Solid epoxy resin Epoxy novolac resin Solvent Dicyandiamide BDMA 100 100 As required 16 2-4... 

Solid epoxy resin (40% solids) Epoxy novolac resin (85% solids) Dicyandiamide BDMA 212 37.5 12 2.0... 

EPI CURE 3253 BDMA Ancamine K61B CAPCURE EH-30 Versamine EH-30 DMP-30, tri (s-dimethylaminoethyl) phenol DMP 10, dimethy-laminomethyl phenol Benzyldimethylamine Tertiary amine salt Tertiary amine Tertiary amine 575-625 180-380 10 Resolution Resolution Resolution Cognis UCB chemical... 

Source Du Pont Methylamines Bulletin aMMA = Monomethylamine bDMA = Dimethylamine CTMA = Trimethylamine... 

SYNS ARALDITE ACCELERATOR 062 BDMA BENZYLDIMETHYLAMINE BENZYL-N SI-DIMETHYLAMNE N-BENZYLDIMETHYLAMINE NJSI-DIMETHYLBENZENEMETHANAMINE N-(PHENYLMETHYL)DIMETHYLAMINE SUMINE 2015... 

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