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. 

Composite Particles, Inc. reported the use of surface-modified rubber particles in formulations of thermoset systems, such as polyurethanes, polysulfides, and epoxies [95], The surface of the mbber was oxidized by a proprietary gas atmosphere, which leads to the formation of polar functional groups like —COOH and —OH, which in turn enhanced the dispersibility and bonding characteristics of mbber particles to other polar polymers. A composite containing 15% treated mbber particles per 85% polyurethane has physical properties similar to those of the pure polyurethane. Inclusion of surface-modified waste mbber in polyurethane matrix increases the coefficient of friction. This finds application in polyurethane tires and shoe soles. The treated mbber particles enhance the flexibility and impact resistance of polyester-based constmction materials [95]. Inclusion of treated waste mbber along with carboxyl terminated nitrile mbber (CTBN) in epoxy formulations increases the fracture toughness of the epoxy resins [96]. 

Consist of a range of chemicals which promote cross-linking can initiate cure by catalysing ( catalysts , hardeners, initiators), speed up and control cure (activators, promoters) or perform the opposite function (inhibitors) producing thermosetting compounds and specialised thermoplastics (e.g. peroxides in polyesters, or amines in epoxy formulations). The right choice of a cure system is dependent on process, process temperature, application and type of resin. 

Epoxy-DICY systems, 10 454 Epoxy equivalent weight (EEW), 10 399 Epoxy ester alkyd resins, 2 165-166 Epoxy esters, 10 380-384, 443 Epoxy formulations, performance of, 10 428 Epoxy groups, 10 567 hydrolysis of, 10 358 acid-catalyzed cross-linking of, 15 171 Epoxy molding compounds (EMC), 10 373, 430 34, 458... 

Controlled release epoxy formulations in which tin is chemically anchored as tributyltin carboxylate to the polymer chain are discussed. NMR evidence is presented to establish that rapid exchange exists in tributyltin carboxylates. Consequently, even the interfacial reaction between tributyltin carboxylates and chloride is very fast equilibrium constants are reported for the reaction between tributyltin acrylate in hexane and sodium chloride in water. IR spectra, gas chromatographic retention time, chloride assay, and the complex intensity pattern of the molecular ion peaks in the mass spectrum show that the product of the reaction is tributyltin chloride, suggesting that it is the chemical species responsible for antifouling activity in marine environment. 

Figure 2. Infrared spectra of baked and unbaked Type I urea-urethane/epoxy formulations respectively.

Figure 3. Infrared spectra for Type II urea-urethane/epoxy formulations, respectively, showing decreases in the intensity of the urethane absorption as the1 temperature of the cure reaction is increased from 50-180°C.

Other effects were more selective. While recycle usually lowered impact strength and heat deflection temperat ire, pre-soaking polyamine recycle surprisingly improved both of these properties. While recycle usually lowered volume resistivity, polyamide recycle improved it. Finally, adhesion of epoxy formulations to the aluminum mold, in spi/ e of wax and silicone mold release agents, was dramatically increased by the use of presoaked recycle, especially in the ai ydrlde system, suggesting unexpected usefulness in epoxy adhesive formulations. 

Most epoxy formulations contain diluents, fillers or reinforcement materials, and toughening agents. Diluents may be reactive (mono- and diepoxides) or nonreactive (di-n-butyl phthalate). Toughening (flexibilizing) agents such as low-molecular-weight polyesters or... 

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. 

Hadad, D. K.., Fritzen, J. S., May, C. A. Exploratory Developments of Chemical Quality Assurance and Composition of Epoxy Formulations, Air Force Materials Laboratory Technical Report, AFML-TR-77-217, (1978)... 

Adding fillers to epoxy formulations can reduce the magnitude of the internal stresses developed upon setting because they act to reduce the difference between the... 

Durcon. A series of cast, plastic, epoxy formulations manufd by the Duriron Co for use in corrosion resistant equipment such as pumps, valves, fans and others Ref CondChemDiet (1961), p426... 

The interfacial adhesion between dispersed particles and the matrix can be improved by functionalizing the core-shell particles with any chemical group that can react with the thermosetting polymer. For example, glycidyl methacrylate can be introduced in the shell composition to incorporate functional groups that can react with epoxy formulations. 

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.)... 

Romano et al. (1994) introduced both CTBN and a linear phenoxy thermoplastic in an epoxy formulation. The resulting morphologies were strongly dependent on heating rates. They included subdomains and interconnected zones. A combination of 30 phr phenoxy and 15 phr CTBN, associated with a slow cure schedule, greatly improved the peel shear strength. 

The best generic coatings for carbon steel that may be surrounded by wet insulation in the 140° to 250° F (60° to 120° C) range are the epoxy phenolic and the amine-cured coal tar epoxy formulations. 

One problem with early epoxy formulations is that they cured to a relatively brittle material. By using reactive flexibilizers, such as polysulfides, epoxy adhesive formulators have obtained the flexibility required for many applications in this industry. Polyamides and even coal tars have also been used to provide flexibility to epoxy base resins. 

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. 

Since epoxy formulations are generally good thermal insulators, the exotherm will depend on the mass of the system. A high rate of exotherm is needed with some epoxy adhesive systems to achieve practical curing rates. However, excessively high exothermic temperatures can result in bubble formation, thermal degradation, and even a potentially hazardous situation. Control of the exotherm is, therefore, a very important factor in formulating epoxy adhesives. 

The catalytic curing agents commonly used include tertiary amines, Lewis acids and bases, and dicyandiamide. Since their function is truly catalytic, the catalyst is added at relatively low concentrations (0 to 5% by weight) to the epoxy formulation. Homopolymerization generally requires both the presence of catalysts and elevated temperatures for the reaction to proceed. Like the polyaddition reaction, the homopolymerization reaction is accelerated by hydroxyl groups or tertiary amines. 

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... 

Reactivity can also be increased by externally heating the epoxy formulation to a preselected curing temperature. Epoxy resin reactions roughly obey Arrhenius law that for every 10°C rise in temperature, the reaction rate doubles. Certain epoxy resin systems must be heated for any reaction to take place at all. This is beneficial in that these latent adhesive formulations are one-component products that do not require metering or mixing yet have long, practical shelf lives. 

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. 

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