Epoxy resins description

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. ... 

Materials Description. Three CIBA-GEIGY epoxy/hardener systems were studied Araldite 6010/906, Araldite 6010/HY 917 and Araldite 6010/972 with stoichiometries 100/80, 100/80 and 100/27, respectively. Araldite 6010 was a DGEBA epoxy resin. The hardeners 906, HY 917 and 972 were, respectively, methyl nadic anhydride (MNA), methyltetrahydro phthalic anhydride (MTPHA) and methylene dianiline (MDA). These systems were investigated previously for the matrix controlled fracture in composites (6-8). The curing cycles used can be found in (6). The ideal chemical structures of the systems are shown in Table I. Neat resins were thoroughly degassed and cast into 1.27 cm thick plates for preparation of test specimens. 

Latexes are usually copolymer systems of two or more monomers, and their total solids content, including polymers, emulsifiers, stabilizers etc. is 40-50% by mass. Most commercially available polymer latexes are based on elastomeric and thermoplastic polymers which form continuous polymer films when dried [88]. The major types of latexes include styrene-butadiene rubber (SBR), ethylene vinyl acetate (EVA), polyacrylic ester (PAE) and epoxy resin (EP) which are available both as emulsions and redispersible powders. They are widely used for bridge deck overlays and patching, as adhesives, and integral waterproofers. A brief description of the main types in current use is as follows [87]. 

This article will review the impact of two powerful new techniques for characterizing epoxy resins at the molecular level — Fourier transform infrared spectroscopy (FT-IR) and high resolution nuclear magnetic resonance (NMR) of solids. Fortunately, these two techniques are not inhibited appreciably by the insoluble nature of the cured resin. Consequently, substantial structural information at the molecular level can be obtained. In this article, the basis of the methods will be briefly described in order to appreciate the nature of the methods followed by a description of the work on epoxies to date and finally some indication will be given of the anticipated contributions of these methods in the future. 

Although the simple rate expressions, Eqs. (2-6) and (2-9), may serve as first approximations they are inadequate for the complete description of the kinetics of many epoxy resin curing reactions. Complex parallel or sequential reactions requiring more than one rate constant may be involved. For example these reactions are often auto-catalytic in nature and the rate may become diffusion-controlled as the viscosity of the system increases. If processes of differing heat of reaction are involved, then the deconvolution of the DSC data is difficult and may require information from other analytical techniques. Some approaches to the interpretation of data using more complex kinetic models are discussed in Chapter 4. 

Figure 3. Effect of EME 58 (58 wt% mercaptoester units co-polymer) coupling agent concentration on the peel strength of flexible epoxy (amine-cured)/AD = acetone-degreased steel test panels following (a) I day and (b) 3 day exposure to 57°C condensing humidity. See Appendix 4 for epoxy resin and cure description.

For commodity applications, there are four major classes of resins that are used in FRP applications. They are phenolic resin, epoxy resin, unsaturated polyester resin, and epoxy vinyl ester resins. A more complete description of these types of resins and their many variations can be found in Handbook of Thermoset Plastics. This is not a comprehensive list of resins used in composite manufacture, as commodity materials like polyurethanes and isocyanurate resins are sometimes used as well to make FRP parts. However, these materials are not covered in this chapter owing to their limited use, but, the principals of fire safety that apply for the resins described subsequently apply to these materials as well. 

A review is presented of the electrical properties of polymers filled with different types of conducting particles. Following a theoretical description of a general effective media equation, experimental conductivity-volume fraction data for thermoplastic filled with vanadium oxide particles as well as thermosetting polymer composites, were fitted to the equation. The calculated property-related parameters in the equation are discussed. Data are given for PVC, HDPE, LLDPE, LDPE, and epoxy resin. 12 refs. 

A considerable number of detailed descriptions on synthesis, production, and applications of epoxy resins exists. Because the aim of this chapter is the application of cationic initiators, and more particularly photoinitiators, to the polymerization of epoxies leading to cross-linked products (curing reaction), only litterature dealing with these aspects will be cited. For the general aspects of epoxy resins the scientific and patent literature may be found in detailed reviews [119,120] and classical books [121-123]. 

One result of this development work is an instrument for accurately measuring a key property of can coatings, the sterilisation resistance. First, however, a brief description of can coatings and some of their properties is in order. The discussion will be limited to coatings to be applied to the interior of food-or beverage-containing cans since this application requires the highest chemical resistance. Most of the work described has been carried out with can lacquers of the solid epoxy resin/phenolic-formaldehyde (E/PF) type as these are the predominant type used in Western Europe. 

Methods making use of epoxy resins, resulting in polished sections in only a few minutes, are discussed first, followed by details of impregnation and encapsulation. Equipment and techniques for grinding and polishing, including thin-section procedures, are described. The use of Hyrax , a synthetic resin with an index of refraction of 1.70, is discussed, followed by a description of a recommended method for refractive-index determination of particles mounted on a thin film of epoxy. 

When the number of repeating units in a polymer chain is low, that is when the molecular weight of the polymer is low (2000-10000 g mol ), the polymer is defined as a resin, provided it possesses sufficient numbers of active sites in its structures for chemical cross-linking to occur. The resins can form three-dimensional network structures if sufficient external energy (heat/light/radiation) is applied, with or without the use of any other chemical(s) in their finished state. They are free flowing materials of low viscosity. Polyester resins, epoxy resins, and polyurethane resins are examples of this type of polymer. This book contains descriptions of the different types of resins derived from various vegetable oils. 

For the epoxy resins studied, the mobility factor based on heat capacity coincides very well with the diffusion factor, calculated from the nonreversing heat flow via chemical kinetics modelling, and describing the effects of diffusion control on the rate of conversion of the cure reaction. Although the two resins behave quite differently, this coincidence between the mobility factor and diffusion factor is valid for both systems. Therefore, the mobility factor can be used for a quantitative description of then-altered rate of conversion in the (partially) vitrified state for the decrease in rate during vitrification, the increase in rate during devitrification and the diffusion-controlled rate in the (partially) vitrified region in between both processes. 

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. 

The most commonly used materials for permanently filhng through holes include singlecure (thermal) resins, photoimageable dielectrics, conductive pastes, and the dual-cure (UV -i-thermal) epoxy resin utilized in the Noda screen flat plug process. Following are brief descriptions and comparisons of the characteristics of each of these types of via-fill materials. 

Fig. 11.8 Schematic description of a transistor chip with an ISFET and a reference gate (cf [39]). 1 Epoxy resin, 2 compartment filled with buffered agarose, 3 reference gate, 4 glass capillary, 5 ion-sensitive gate...

Other than the brief description of their use with commercial epoxy resins, little is known of their photochemistry of their mechanism of initiation. 

Dow Chemical Company, Production Description - DEN Epoxy Novolac Resins, form No. 170 - 143B (1967). 

In commercial practice, the taffy method is used to prepare lower MW solid resins, ie, those with maximum EEW values of about 1000 (type 4 ). Upon completion of the polymerization, the mixture consists of an alkaline brine solution and a water-resin emulsion. The product is recovered by separating the phases, washing the taffy resin with water, and removing the water under vacuum. One disadvantage of the taffy process is the formation of insoluble polymers, which create handling and disposal problems. Only a few epoxy producers currently manufacture SERs using the taffy process. A detailed description of a taffy procedure follows (24). 

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