Diglycidyl Ether of Bisphenol A DGEBA

Epoxy resins were first introduced by Ciba-Geigy, Ltd., in 1946 although their development began decades earlier. The most common commercial epoxy resin is formed from the reaction of bisphenol A and epichlorohydrin. This resin is known as the diglycidyl ether of bisphenol A or DGEBA (Fig. 2.4). 

The addition of NaOH catalyzes the reaction to produce the chlorohydrin intermediate, acts as the dehydrohalogenating agent, and neutralizes the formed HC1. The reaction generally occurs over 16 h at 110°C. The caustic is added slowly as a 30% aqueous solution. The resulting organic is separated, dried with sodium sulfate, and fractionally distilled under vacuum. 

FIGURE 2.4 Synthesis of DGEBA epoxy resin from bisphenol A and epichlorohydrin/ 

TABLE 2.1 Effect of Varying Reactant Ratios on Molecular Weight of Epoxy Resins7 

Mole ratio epichlorohydrin/ bisphenol A Mole ratio NaOH/ epichlorohydrin Softening point, °C Molecular weight Epoxide equivalent Epoxy groups/ molecule 

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Diglycidyl ether of bisphenol A (DGEBA, MW 340 Da) and 4,4 -dihydroxy-diphenylmethane (DHDPM, MW 200 Da) were analysed by SEC-MALS [784]. DGEBA and DHDPM are the basic oligomers of epoxy resins and phenol-formaldehyde condensates, respectively, which are widely used in the electronic and automotive industries. Excellent reproducibility ( 1 %) and good accuracy (better than 10%) were observed. SEC has also been used for the determination of mineral oil in extended elastomers [785] and in PS [178]. With heptane containing 0.05% isopropanol as the mobile phase, mineral oil is completely unretained and elutes before the solvent via SEC all other components in a PS extract are retained on silica and elute after the solvent peak. 

Shell s Epon 828, a blend of oligomers of diglycidyl ether of bisphenol A (DGEBA, n=0), was used. 

Dezincing, lead refining by, 14 754-755 DGEBA-aromatic polyamine adduct system, 10 416, 417. See also Diglycidyl ether of bisphenol A (DGEBA)... 

Yamani and Young (5) applied the theory to explain the plastic deformation of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin cured with various amount of triethylene tetramine (TETA). They found that the theory gave a reasonable description for the resins below the glass transition temperatures T. ... 

We have undertaken a systanatic investigation of the effect on cured resin physical properties of various alkyl groups on the MFD aromatic ring. In this report we present static and dynamic mecdaniccd properties, density measurenents, and glass treuisition tenperature (Tg) measuremmits of diglycidyl ether of bisphenol-A (DGEBA) cured with various alkylated MFD s. 

Diglycidyl ether of bisphenol-A (DGEBA), epoxy resin (YD 128, Kuk Do Chem., Mn = 378), and bisphenol-A dicyanate (BPACY, Arocy B-10, Ciba-Geigy) were used as the thermoset resin. 4,4 -diaminodiphenyl sulfone (DDS, Aldrich Chem. Co.) was used as a curing agent for epoxy. Polyetherimide (PEI, Ultem 1000, General Electric Co., M = 18,000) and 2-methyl imidazole (2MZ, Aldrich Chem. Co.) were used as the thermoplastic modifier and catalyst. 

The epoxy resin can be defined as any molecule that contains two or more alpha-epoxy groups which can be reacted to form a thermoset system. An example of a difunctional epoxy resin is diglycidyl ether of Bisphenol-A (DGEBA) which is formed... 

Table 1. Gk values measured at room temperature for Diglycidyl ether of bisphenol A (DGEBA) epoxy resins cured with various hardeners 11...

The complex sorption behavior of the water in amine-epoxy thermosets is discussed and related to depression of the mechanical properties. The hypothesized sorption modes and the corresponding mechanisms of plasticization are discussed on the basis of experimental vapor and liquid sorption tests, differential scanning calorimetry (DSC), thermomechanical analysis (TMA) and dynamic mechanical analysis. In particular, two different types of epoxy materials have been chosen low-performance systems of diglycidyl ether of bisphenol-A (DGEBA) cured with linear amines, and high-performance formulations based on aromatic amine-cured tetraglycidyldiamino diphenylmethane (TGDDM) which are commonly used as matrices for carbon fiber composites. 

The increase of the glass transition temperature with the conversion of the thermosetting polymer may be followed by DSC. Figure 4.6 (Montserrat, 1992), shows DSC thermograms in the heating mode, for a system based on diglycidyl ether of bisphenol A (DGEBA)-phthalic anhydride and a commercial tertiary amine as initiator, cured at 80°C (a) and 130°C (b), for different times, tc (h). The initial formulation exhibits a shift in the baseline at Tg0= —23.2°C (defined at the midpoint of the shift). Tg increases with cure time at constant temperature. The completely cured... 

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). 

Figure 8.1 Cloud-point temperatures versus volume fraction of modifier, for mixtures of diglycidyl ether of bisphenol A, DGEBA (n = 0.15) with two CTBN copolymers with different acrylonitrile content 18 and 10 wt%. (Reprinted from Verchere et ai, 1989, Copyright 2001, with permission from Elsevier Science)...

Figure 8.7 SEM photograph of a fully cured rubber-modified epoxy network. The rubber CTBN (26 wt% AN) is first pre-reacted with a large excess of diglycidyl ether of bisphenol A (DGEBA) to obtain an epoxy-terminated rubber. Then an equivalent of 15 wt% initial CTBN is introduced in DGEBA-4,4 -diamino diphenyl sulfone, DDS, system precured at 135°C (time > tgei) and then postcured at 230°C. Rubber-rich particles are spherical, D 2.8 0.5 gm, and well dispersed. (From LMM Library.)...

Figure 11.11 Cole-Cole plots for networks resulting from the condensation of diglycidyl ether of bisphenol A (DGEBA) and diethyltoluenediamine (ETHA), with various amine/epoxide molar ratios (numbers on the figures). Reprinted from Tcharkhtchi et at. 1998. Copyright 2001 with permission from Elsevier Science.

For many usual, moderately polar networks, such as epoxides of the diglycidyl ether of bisphenol A (DGEBA) diamine type, or vinyl esters, Hs —Hw, so that the equilibrium concentration appears almost temperature-independent. For most of the less polar networks such as polyesters or anhydride-cured epoxies, Coo (or Wro) increases slightly with temperature AW /AT 0.01 0.02% K 1 between 20 and 50°C. 

The/flc-ClRe(CO)3(4,7-Ph2-phen) complex has been demonstrated to be a useful spectroscopic probe in the curing of photosensitive epoxy-based materials [100], Emission spectra obtained from a 0.05-mm thickness film of a mixed epoxy system of bisphenol-A/novalac resin (Interz, SU8) and diglycidyl ether of bisphenol-A (DGEBA) containing cation-generating triarylsulfonium hexafluo-roantimonate salts as photoinitiators (Union Carbide, Cryacure UVI-6974) and... 

Diluents are higher-MW components than solvents that are also added to the epoxy adhesive formulation to lower the viscosity and modify processing conditions. The primary function of a diluent in an epoxy resin formulation is to reduce its viscosity to make it easier to compound with fillers, to improve filler loading capacity, or to improve application properties. Solvents, certain curing agents, and flexibilized epoxy resins can also lower the viscosity of epoxy adhesive formulations, but this is not their primary function. The effect of various diluents on the initial viscosity of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin is illustrated in Fig. 6.3. 

Murayama8> studied a series of resins from diglycidyl ether of Bisphenol A (DGEBA) cured with varying quantities of diaminodiphenylmethane (DDM). These cured resins had the same main chain structure, but differed in the degree of crosslinking. Izumo 25) performed similar studies by using diethylenetriamine (DETA) as a... 

Figure 32. The a-relaxation times for the glass formers studied in the present work (cf. Fig. 27). In addition data of diglycidyl ether of bisphenol A (DGEBA) and phenyl glycidyl ether (PGE) are included time constants as obtained from DS data sets of m-TCP and 2-picoline were combined with xrl from conductivity and light scattering measurements, respectively, (a) Relaxation times as a function of T Ts. The systems differ by the slope of Ta at Tg. (b) By plotting xr, as a function of the rescaled temperature z = m(T/Tg — 1) the effect of an individual fragility is removed and a master curve is obtained for systems with similar To. Solid line represents Eq. (41) with Kf) — 17. (c) Upper part master curve for xa according to Eq. (42). Deviations of the data from Eq. (42) (solid line) indicate break-down of the VFT equation. Lower part The ratio lg(ra/rvft) shows deviations from a VFT behavior most clearly. Dashed vertical lines indicate shortest and fastest tx, respectively, observed. All the figures taken from Ref. [275].

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