Additives epoxy formulations

Tetrahydrofurfuryl alcohol is used in elastomer production. As a solvent for the polymerization initiator, it finds appHcation in the manufacture of chlorohydrin mbber. Additionally, tetrahydrofurfuryl alcohol is used as a catalyst solvent-activator and reactive diluent in epoxy formulations for a variety of apphcations. Where exceptional moisture resistance is needed, as for outdoor appHcations, furfuryl alcohol is used jointly with tetrahydrofurfuryl alcohol in epoxy adhesive formulations. 

Flexibilized epoxy resins are important structural adhesives [69]. Liquid functionally terminated nitrile rubbers are excellent flexibilizing agents for epoxy resins. This liquid nitrile rubber can be reacted into the epoxy matrix if it contains carboxylated terminated functionalities or by adding an amine terminated rubber. The main effects produced by addition of liquid nitrile rubber in epoxy formulations is the increase in T-peel strength and in low-temperature lap shear strength, without reducing the elevated temperature lap shear. 

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

Tetrabromobisphenol A epoxy resins are available as viscous liquids with several molecular weight ranges. As the bromine content increases, the flame resistance increases but the viscosity of the resin generally increases as well. They are primarily used as an additive in formulations producing epoxy laminates and adhesives that require improved resistance to ignition. 

This transformation or conversion is accomplished by the addition of a chemically active compound known as a curing agent or catalyst. Depending on the particular details of the epoxy formulation, curing may be accomplished at room temperature, with the application of external heat, or with the application of an external source of energy other than heat such as ultraviolet (uv) or electron beam (EB) energy. 

Properties often used by epoxy resin manufacturers to specify particular grades of resin include the epoxy content, viscosity or softening point, and color. In addition, properties such as density, vapor pressure, flash point, refractive index, solubility characteristics, and hydroxyl content are often reported. The important properties of uncured epoxy formulations with regard to most adhesive applications are... 

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. 

The addition of particulate fillers generally decreases compression fatigue, but increases ultimate compressive modulus and compressive yield strength, because of a stiffening effect. Compressive strength as a function of filler loading is shown for a cured epoxy formulation in Fig. 9.7. 

Fillers. Fillers are added in epoxy formulations to obtain the desired properties in a system. Additionally, they reduce the cost of formulations. The amount of filler by weight that can be incorporated into an epoxy resin will depend on the filler s particle size, density and oil absorption properties. Within each family of filler there are products that impart different properties because of varying coarseness, impurity level and method of preparation. The effect of addition of fillers to epoxy formulations is to ... 

Epoxies are excellent electrical insulators. Electrical properties are reduced on increasing the polarity of the molecules. Addition of metallic fillers, metallic wools and carbon black convert the non-conductive epoxy formulation into an electrically conductive system. Non-conductive fillers increase the arc resistance and to some extent increase the dielectric constant. 

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. 

Epoxy resins are amenable to modification in many ways and commercial epoxy formulations often contain a number of materials whose presence serves to modify the properties and characteristics of both uncured and cured epoxy. These additives fall into the following general categories ... 

Polyamides, aromatic amines, cylcoaliphatic amines, reactive diluents, and specialty epoxy resins, which are used as performance additives in epoxy formulations... 

Another class of adherends is that of thermoplastic polymers. In contrast to metal adherends, thermoplastics are not impenetrable and thus absorption effects can be expected in addition to adsorption phenomena. Hence, given sufficient conditions for preferential absorption, a considerable mass uptake by the thermoplastic can occur, potentially resulting in significant stoichiometric imbalances on the epoxy side. Apart from the driving force for absorption of molecules from the liquid epoxy formulation, it is the diffusivity of these molecules within the thermoplastic which plays a major role in the interdiffusion process. In particular, the diffusivity is affected by the mobility of the host molecules. Thus enhancement of diffusivity occurs in the glass transition region and at higher temperatures when intermolecular cooperative motion is activated. 

The hardener portion (Part B) may also be mixed with fillers, diluents, solvents, and other additives. Fillers may be mixed in the resin portion alone or partly in the resin and partly in the hardener portion. Adhesion promoters such as Dow Corning A-180 silane may also be added to enhance the adhesion of the filler particles to the resin or hardener. Examples include several electrically conductive epoxy formulations that were used to evaluate their electrical stability on non-noble metal surfaces. The base epoxy resin was the diglycidylether of bisphenol-F (DGEBF, equivalent wt. = 170 g). Methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, and 4-methylphthalic anhydride were evaluated as curing agents with 4-methylimidazole as a catalyst. The manufacturing procedure was ... 

OTHER INGREDIENTS IN EPOXY FORMULATION Diluents, resinuous modifiers (to affect flexibility, toughness, peel strength, adhesion, etc.), fillers, colorants and dyes, other additives (e.g., rheological additives, flame retardants). 

Furfuryl alcohol is used as a viscosity reducer for epoxy formulations. The addition of furfuryl alcohol to urea-formaldehyde resins improves the craze resistance and heat stability of the adhesives. Furfuryl alcohol serves as an effective wetting agent and solvent for phenolic resins in the manufacture of phenolic resin abrasive grinding wheels. Other miscellaneous uses of furfuryl alcohol include use in alkaline paint strippers and cleaning formulations, as a solvent and carrier for dyes in textile printing, and as a chemical intermediate. 

Epoxy formulations with amine hardeners, cured at room or elevated temperature, have a tendency to become hard and brittle. The addition of polysulphide modifiers increases elasticity, although at the expense of generally lower bond strength. These adhesives permit a fairly thick cement line . 

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