USING EPOXY RESIN

Epoxy Resins. Epoxy resins (qv) are used to cross-link other resins with amine, hydroxyl, and carboxyHc acid (or anhydride) groups. The epoxy group, properly called an oxkane, is a cycHc three-membered ether group. By far the most widely used epoxy resins in coatings are bisphenol A (BPA) (4,4 -(l-methylethyHdene)bisphenol) [80-05-7] epoxy resins. 

Epichlorohydrin and Bisphenol A-Derived Resins. The most widely used epoxy resins are diglycidyl ethers of bisphenol A [25068-38-6] (1) derived from bisphenol A [80-05-7] and epichlorohydrin [106-89-8],... 

Han SS, Kim MK. An improved method for double-isotope and double-emulsion radioautography using epoxy resin sections. Stain Technol 1972 47 291-296. 

The most widely used epoxy resin intermediates (Araldite, Epon, and Epi-Rez) are produced from the reaction of bisphenol A and epichlorohyorin, as shown in Figure 15.7,... 

Epichlorohydrin and Bisphenol A-Derived Resins. The most widely used epoxy resins are diglycidyl ethers of bisphenol A... 

After glass bonding, solution reservoirs were created over access holes to hold reagents. The reservoirs were formed by various methods. Most commonly, short plastic or glass tubings were glued to the access holes using epoxy resin. Septa... 

Epichlorohydrin, or l-chloro-2,3-epoxypropane, is the key raw material in the manufacture of the most widely used epoxy resins known as glycidyl ethers, amines, and esters. The most... 

Organic Base Non-reactive high M.W. tertiary amine End Uses Epoxy resins, ketone solutions... 

The most widely used epoxy resins and adhesives are based on a prepolymer made from bisphenol A and epichlorohydrin. On treatment with base under carefully controlled conditions, bisphenol A is converted into its anion, which acts as a nucleophile in an S142 reaction with epichlorohydrin. Each epichlorohydrin molecule can react with two molecules of bisphenol A, once by S 2 displacement of chloride ion and once by opening of the epoxide ring. At the same time, each bisphenol A molecule can react with two epichlorohydrins, leading to a long polymer chain. Each end of a prepolymer chain has an unreacted epoxy group, and each chain has numerous secondary alcohol groups. 

The equipment and the experimental procedures using the C02-methanol medium have already been described in previous papers. . For the photoelectrochemical experiments, a stainless steel pressure vessel was equipped with a 2-cm thick quartz window for illumination, p-type InP and GaAs wafers were cut into ca. 0.4 cm x 0.5 cm electrodes and were mounted using epoxy resin. Ohmic contact was made with successive vapor deposition of Zn (30 mn) and Au (100 nm), which was annealed afterward at 425 C in Ar. A silver wire (0.8 mm dia) was used as a quasi-reference electrode (Ag-QRE, ca. +80 mV vs. SCE). A Pt wire (0.8 mm dia) was used as the counter electrode. The photocathode was etched in hot aqua regia for ca. 5 s before each experiment. The electrolyte solution [3 cm, 0.3 mol dm" tetrabutylammonium perchlorate (TBAP) in CH3OH] was placed in a glass cell liner in the stainless steel vessel. Gases were introduced into the pressure vessel and were left to equilibrate for one hour at the desired pressure (1 to 40 atm). 

MONOMERS. Amine hardener, 4,4 -methylene-bis-(cyclohe.xylamine) (PACii ), was distilled under reduced pressure and stored under dry argon. It was melted under dry argon before use. Epoxy resin, diglycidyl ether of bisphencl A (DGEBA), had an epoxy equivalent weight of approximately 175 and was used without further purification. 

Like most other synthetic resins, epoxy resins have a limited tolerance for certain solvents. A 40% acetone solution can be prepared with an epoxy resin (mol wt 2900), but a 20% solution cannot. Acetone is not a true solvent because a true solvent provides infinite dilution of the resin. The dilution tolerance may be extended by adding alcohols and aromatic hydrocarbons many such solvent mixtures have become established in epoxy resin based coatings. The study of alternate solvent mixtures has been systematized and simplified using epoxy resin solubility maps and ternary diagrams. 

In recent years, there have been some interesting developments in epoxy-modified mortar and concrete in Germany. The developments include a one-component epoxy resin system for the cement modifier and a dry mortar using epoxy resin. The former does not need any hardeners added at the construction site. The latter is produced as a dry mixture of an epoxy resin with a hardener, cement, and aggregates, and can be applied by adding only water in the field. 

Y. Ohama, K. Demura and T. Endo Properties of polymer-modified mortars using epoxy resin without hardener, in Polymer-Modified Hydraulic-Cement Mixtures, STP 1176, American Society for Testing and Materials, Philadelphia (1993), pp.90-103. 

The most widely used epoxy resins are reaction products of either bisphenol A or a novolac phenolic resin with epichlorhydrin. When used to manufacture corrosion-resistant structures for use in the chemical process industry, epoxy resins are generally hardened with either aromatic or cycloaliphatic amines. The hardeners for epoxy resins are, with few exceptions, added at levels varying from 20phr (parts per hundred resin) to lOOphr. This means that the hardener is actually quite a high proportion of the matrix resin and has quite a profound effect on the mechanical and corrosion properties of the cured resin. Thus the selection of the most suitable hardener is critical to the eventual success of the application. Epoxy resins have viscosities of several thousand mPas at room temperature, which makes it much more difficult to wet out glass fibre efficiently with them than with polyesters. Wet-out therefore involves heating the resin formulation to between 40°C and 60°C to reduce the viscosity to less than 1000 mPas. 

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