Epoxy formulation table

Figure 12.7 Plot of yield stress and modulus data according to Kitagawa s equation (T0 = 22°C) for different epoxy formulations (see Table 12.1 for abbreviations). (Reprinted from Cook et al., 1998, Copyright 2001, with permission from Elsevier Science.)... 

Typical glass transition temperatures for adhesive resins are shown in Table 3.9. Note, however, that the Tg for epoxy adhesives can vary significantly with their formulation. Glass transition temperatures for several epoxy formulations are shown in Table 3.10. 

DEAPA was used in several early commercial epoxy adhesive formulations. Schonhom and Sharpe9 have shown that this amine is surprisingly effective in reducing the surface tension of epoxy resins (Table 5.4). It is speculated that the utility of DEAPA adhesives is in part due to better wetting than other epoxy formulations. 

TABLE 8.2 Typical Flexible Epoxy Formulations and Their Effect on Properties5... 

Fillers and extenders are used in epoxy adhesive formulations to improve properties and to lower cost. Properties that can be selectively improved include both the processing properties of the adhesive as well as its performance properties in a cured joint. However, the use of fillers can also impair certain properties. Typically, the formulator has to balance the improvements against property decline. The advantages and disadvantages of filler addition in epoxy formulations are listed in Table 9.1. Common fillers used in epoxy formulations and the properties that they are used to modify are shown in Table 9.2. 

Fillers generally represent one of the major components by weight in an adhesive formulation. However, their concentration is quite often limited by viscosity constraints, cost, and negative effects on certain properties. The degree of improvement provided by a filler in an epoxy formulation will heavily depend on the type of filler and its properties (particle size, shape, size distribution, and concentration), surface chemistry, dispersion characteristics, dryness, and compatibility with the other components in the formulation. Table 9.3 summarizes the properties of selected fillers. 

TABLE 9.1 Advantages and Disadvantages of Fillers in Epoxy Formulations (Depending on Type of Fillers Employed)1... 

One of the distinct advantages of epoxy adhesives is that they can be cured at room temperature or even at lower temperatures. Epoxy adhesives are often divided into room temperature curing types and elevated-temperature curing types. This chapter discusses room temperature epoxy formulations. The major advantages and disadvantages of room temperature curing epoxy adhesives are shown in Table 11.1. 

As a family of curing agents for epoxy resins, the amidoamines are lower in viscosity than the polyamides. They exhibit very good adhesive properties due to their chemical structure and easy penetration. Amidoamine cured epoxy adhesives have shown very good properties on concrete and other porous substrates. They cure extremely well under humid conditions. In fact amidoamine cured epoxy formulations have been used to cure underwater in certain applications. A typical general-purpose room temperature curing epoxy-amidoamine system is described in Table 11.7. This adhesive is used as a general-purpose metal-to-metal adhesive and body solder in the automotive industry. 

Table 12.2 describes an epoxy formulation cured with DEAPA. Cure conditions of only 45 min at 100°C are adequate to obtain high bond strength on aluminum and moderately better performance at elevated temperatures than that for systems cured at room temperature. In this formulation the low-molecular-weight, high-epoxy-content resin (EPON 1009)... 

A typical formulation for a metal-to-metal adhesive-sealant that is cured with a combination of phthalic anhydride and pyromellitic anhydride is shown in Table 12.6. Table 15.9 shows the high-temperature properties of another epoxy formulation cured with pyromellitic dianhydride. Epoxy formulations cured with pyromellitic dianhydride (PMDA) show good short-term thermal stability in the temperature range of 150 to 230°C. 

Both GPC and DSC show that impurities or reaction byproducts in commercial TGMDA resins increase the rate of reaction. This effect is illustrated in Figures 8 and 9 where the epoxy/amine equivalent ratios are held constant. Impurities also tend to lower g, reduce the gelation time, increase M at g, and increase Ofjnai The magnitude of these effects are particularly notable upon comparing the DSC parameters of the TGMDA and Residue formulations (Table IV). 

There are many metal-type additives in epoxy adhesives and for the sake of analytical input to these products for metal content the following formulations were prepared to study the effect of different sample preparation methods as applied to these products. Four typical epoxy formulations containing active monomer/resin, colorants, curatives and fillers were prepared in the laboratory as part of a study of sample preparation methods for the determination of the concentration of the Ge(AcAc)BF4 additive. The four preparations were formulated as shown in Table 6.14. 

Two-component IPN foams consisting of polyurethane and epoxy were prepared by the one-shot, free-rise method. The effects of PU/E ratio on the sound absorption and mechanical energy attenuation characteristics were determined with varying levels of different fillers and plasticizers. The formulations (Table IX) were based on the best elastomer results. An average of over 90X absorption was obtained at high frequencies by the Impedance tube method. However, this average drops dramatically at low frequencies. This reduction may be seen in Figs. 3 and 4 for 90/10 and 70/30 IPN foams vlth 20X... 

Although DGEBA resins provide the backbone of most epoxy formulations, they may be blended with other types to achieve modifications. Epoxy novolacs, having higher functionality, increase the cross-linking density, which improves heat resistance but decreases impact resistance. Incorporation of epoxidized oils increases flexibility at the expense of heat and chemical resistance. Low-viscosity polyfunctional epoxies based on polyols or polyhydric phenols reduce viscosity and can increase functionality without impairing cured properties. Monofunctional reactive diluents will also decrease viscosity and form part of the polymer backbone, to impart a measure of flexibility without the possibility of migration. Properties of commercially available epoxy resins and diluents from various suppliers are listed in Table 1. 

The viscosity of the epoxide prepolymers in many instances is reduced by additions of thin liquid epoxy compounds fliat may include cycloaliphatic epoxides or lactones. Various epoxidized vegetable oils, like epoxidized linseed, sunflower, soybean, and others are also used in some formulations. Table 3.4. lists come cycloaliphatic epoxy monomers used for such purposes. Vinyl ethers polymerize at a faster rate than do cycloaliphatic epoxides. They are, therefore, included in some formulations. Other materials fliat are included for such purposes or to control viscosity can be epoxy novolacs, glycidyl ethers of long chain alcohols. To control viscosity, polyols might also be used, because it is assumed that hydroxy group bearing compounds crosslink with the epoxy resins. 

Fillers. Fillers (qv) are incorporated in epoxy formulations to enhance or obtain specific desired properties in a system. The tsq)e and amoimt of filler used are determined by the specific properties desired. Fillers can also reduce the cost of epoxy formulations. Inert commercial fillers (qv) can be organic or inorganic, and spheroidal, granular, fibrous, or lamellar in shape. The properties of commercial fillers are given in Table 21, and some effects on epoxy resins are shown in Tables 22 and 23. Some formulations contain up to 90 wt% fillers. For certain applications, fillers can have significant effects on thermoset morphology, adhesion, and the resulting performance. 

At ambient temperatures epoxy formulations can be provided that will resist normal atmospheric corrosion. The general resistance is shown in Table 8.6 and the operating temperature ranges are given in Table 8.7. 

After the adhesive is cured and the die is packaged, any further release of volatiles by the adhesive is generally undesirable, particularly if the volatiles can combine with water vapor to cause corrosion. Table 3 shows two epoxy formulations which are representative of the best one-component silver-filled epoxies used for electronic assembly up to about 1980. Epoxy A in Table 3 is cured with a latent amine known as dicyandiamide (dicy) ... 

Epoxy systems used in structural applications, whether as adhesives or the matrix of fibre-reinforced composites, are normally cured under some pressure and can be regarded as in closed containers. Studies on the kinetics and mechanisms of cure chemistry are often conducted without pressure in containers essentially open to the atmosphere. Extensive thermal analysis examinations at this Laboratory on a range of epoxy formulations have shown that for such fundamental quantities as the heat of reaction substantially different values can be obtained by using open or hermetic pans (Table 2). These differences are apparent with both the TDI-DMA adduct and dicyandiamide as curing agent but not with DDS. 

Because of the presenee of fluorinated free-dandling ehains in the HBP moleeule, we were interested in investigating the surface effect of the presenee of this additive in the photocurable formulations. Different epoxy formulations, in the presenee of different amount of HBP, were coated on a glass substrate and photocured. Contact angle measurements were performed on UV cured films. The data reported in table 10 show an inerease on hydiophobicity in the presenee of fluorinated HBP. 

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