Epoxy resins characteristic group

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]. 

These findings suggest strongly that the composition of the elastomeric molecule and the nature of the functional groups affect its compatibility and rate of reaction with the epoxy resin, which in turn affect the molecular and morphological structure of the heterophase system. These data indicate the importance of the acrylonitrile comonomer and the carboxyl groups in controlling the polarity of the rubber, and subsequently its compatibility characteristics with the epoxy. We could also... 

The base epoxy resin can be either liquid or solid. As molecular weight increases, the epoxy equivalent weight and the number of hydroxyl groups available for reaction increase. Waterborne epoxy adhesives provide excellent adhesion to metals and other high-energy substrates. Modified waterborne epoxy adhesives can also provide good adhesion to substrates such as vinyl and flexible plastic film. Characteristics of these epoxy dispersions are summarized in Table 4.6. 

The primary and secondary amines are discussed in this section. The secondary amines are derived from the reaction product of primary amines and epoxies. They have rates of reactivity and crosslinking characteristics that are different from those of primary amines. The secondary amines are generally more reactive toward the epoxy group than are the primary amines, because they are stronger bases. They do not always react first, however, due to steric hindrance. If they do react, they form tertiary amines. Tertiary amines are primarily used as catalysts for homopolymerization of epoxy resins and as accelerators with other curing agents. 

Ultrahigh-molecular-weight epoxy resins can be used directly as a thermoplastic adhesive. The hydroxyl groups and good wetting characteristics provide for good adhesion to many surfaces. These adhesives are prepared in film form by solvent casting or extrusion. 

FTIR spectroscopy was used for the analysis of ultrathin organic films on metals. FTIR in the reflection mode (IRRAS) was used to study the interaction of ultrathin films of dicyandiamide (hardener of most one-pack epoxy resins) with various substrates, model ones such as gold or zinc and industrial ones such as steel and zinc-coated steels. Pure zinc surfaces and, to a lesser extent, zinc-coated steels are shown to react with dicyandiamide after heating at 180 C, as evidenced by the frequency shift of the absorption band characteristic for nitrile groups. Some mechanically tested specimens are then analysed, after failure, by FTIR microspectrometry. The spectra obtained, corresponding to the fracture initiation zone which is about 100 micrometers in diameter, indicate the presence of an ultrathin layer of modified polymer still covering the substrate. 28 refs. 

Chemical characteristics. Epoxy resins are a group of cross-linking polymers and are sometimes known as the oxirane group which is reactive toward a broad range of curing agents. The curing reactions... 

Epoxy resins are characterised by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopic analysis. Detailed description of various spectroscopic analyses has already been discussed in Chapter 1. In FT-IR spectra, peaks at 890 cm" to 910 cm" are attributed to an epoxy group. A hydroxyl group is indicated by a broad band at 4000 cm"E The characteristic proton NMR peaks for epoxy resin appear at 2.8-3.2 ppm. 

Lewis and Bronsted acids, activate the epoxy ring toward ring opening by various nucleophilic species, most often hydroxyl or other epoxy groups (Eqs. 2-4). Both types of curatives can take the form of catalytic species, such as tertiary amines and Lewis acids, or coreactants, such as primary amines, mercaptans, and dicarboxylic acids. When the curatives are catalytic species, the properties of the cured adhesive are due primarily to the epoxy resin and the stability/activity of the catalyst in the resin under cure conditions. Coreactant curatives offer much greater latitude in choosing the final cured adhesive properties because the physical characteristics of the... 

Bisphenoi A-epichlorhydrin resins may be blended with a variety of other resins which contain reactive groups. On curing, interaction occurs to give a cross-linked copolymer which exhibits characteristics of the two straight resins. Examples of resins used in conjunction with epoxy resins are ... 

Ink analysis and related analyses of questioned documents have come to rely heavily on IR spectroscopy. As with paints, applications evolved from traditional IR through DRIFTS techniques and now employ principally MSR Inks are analyzed in situ or on sampling substrates such as KBr plates. like paints, inks produce IR spectra representative of mixtures unlike paints, inks rarely have a layered structure. Regardless, spectra of inks do contain information that is useful for classification. For example, a study of 108 inks demonstrated that distinctive absorption bands could be rationalized on the basis of ink composition and then employed to divide the test population into two groups. As shown in Figure 12.7, one group contained C—C stretching characteristic of an epoxy resin and features associated with triarylmethane dyes, as shown in... 

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